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Chapter 6-Scan Parameters
QS4·53287v4
This chapter describes the Scan Parameters area of the Exam window and
provides detailed information about each parameter. These selections allow you
to customize your scans and processing in various ways.
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0AS Is~ MRI System Reference Manual T'hoe htlent MqiMt
Scan Parameters Area
6-2
The default location of the Scan Parameters area is on the right side of the Exam
window, as shown in figure 6- 1. The Scan Parameters area can be displayed on
either side of the Exam window. To change the display location, refer to the
"Displaying the Scan Parameters Area" section in this chapter.
Figure 6-1. The default location for the Scan Parameters area.
This area contains two tabs:
• Basic-Contains the 12 default parameters and any parameters that have been
added to the tab.
• All -Contains a ll the parameters in the Oasis MR System, including the
default parameters listed on the Basic tab.
These tabs are described in the fo llowing sections.
Copyright© 2012 by Hitachi Medical Systems America, Inc. All rights reserved.
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Scan Parameters 0 Basic Tab
The Basic tab contains the following 12 default parameters, as shown in figure
6-2:
• FOV
• TR
• TE
• FA
• Thickness
• Interval
• Multi slice
• Freq#
• Phase#
• NSA
• Sync. Stop Watch
• Gating
FOV 340
1800
150 0
90 __=} .. 1 ... ]
-l.__~~o-o --===?]-+: 1::::::::: 1
-~ r:r:l - ....... 2s_s--==--=-I.. ..
164 =--r_TI Sync Srop•Natct·, off
- off
Figure 6-2. The 12 default parameters on the Basic tab.
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6-4
This tab also contains any parameters that have been added. To add a parameter
to the Basic tab, follow these steps:
I. Click the All tab and drag the scroll box to the bottom of the scro ll bar to
reveal the Config button, as shown in figure 6-3 .
Click MIP Image
DC Level
W-VV1dthl
VV·Levell
Slice Ord A
Slice Ord S
Slice Ord C
Plane Order
Rad1al Stack
L1ne/Box
Gu1de Line
1:.1nM
Sync
ReceiVer C01l
Mode
TM Program
Figure 6-3. Adding a parameter to the Basic tab.
Drag scroll box to bo:tom of scroll bar
Copyright© 2012 by Hitachi Medical Systems America, Inc. All rights reserved.
Note: Changes made to the Basic tab apply to all Exam windows, not just the one currently in use.
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Scan Parameters 0 2. Click the Config button. The Config Setting window opens, as shown in
figure 6-4. Parameter check boxes that are selected and unavailable are the
Basic tab default parameters.
Conflg Setting Slice Plane -- -:l
D 2o13o D Sequence D Echo Time Mode D ShimMode D Oblique
FOV TR TE FA
D IR Pulse Thickness Interval Multi slice
D Multi Echo D Multi Acquisition D Mode D Stacks
Freq# Phase#
OK
..,
Figure 6-4. The Config Setting window.
3. C lick to select each parameter check box that you would like to add to the
Basic tab.
4. C lick OK to add the parameter(s) to the Basic tab and close the Config
Setting window.
To remove a parameter from the Basic tab, follow these steps:
I. C lick the All tab and drag the scroll box to the bottom of the scrol l bar to
reveal the Config button.
2. Click d1e Config button. The Config Setting window opens.
3. Click to clear each parameter check box you wish to remove. The check
mark will be removed and the parameter will not be displayed on the Basic
tab.
4. Click OK to remove the parameter(s) from the Basic tab and close the
Config Setting window.
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0AS Is~ MRI System Reference Manual T'MhtJent MqHt
6-6
All Tab
The All tab, pa1tially shown in figure 6-5, displays all of the scan parameters
including the defaul.t parameters. Because there are so many sca11 parameters,
not all of them can be displayed at once in this sma ll space. Use the scroll bar to
locate the desired set of parameters, or c lick the Overview button (figure 6-5) to
open the ScanParameterList window, which is shown in figure 6-7 and
described in the next section.
Sl1ce Plane
20/30
Sequence
EchoT1me Mode ShortiET
Sh1m Mode ( off - ( Limited
.Parameter
IR Pulse
Thickness
Interval
lv1ultr shce
Figure 6-5. The All tab.
Copyright© 2012 by Hitachi Medical Systems America, Inc. All rights reserved.
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Scan Parameters 0 Scan Parameters Area Buttons
The top of the Scan Parameters area (figure 6-6) contains the following buttons:
Reset
Figure 6-6. The buttons at the top of the Scan Parameters area.
Reset- Resets al l changed parameters to the previously-saved default values.
Overview - Opens the ScanParameterList window, as shown in figure 6-7.
All of the various parameters found under the All tab can be viewed and
changed in this convenient window, rather than scrolling through the categories
in the Scan Parameter· area. Scanning can also be started and scan time can be
mon itored in this window.
Figure 6-7. The ScanParameterList window.
Dy namic scan time table- Opens the Dynamic scan time table window,
which provides a visual display of the execution plan for dynamic scans.
The buttons at the bottom of the Scan Parameters area are used during scanning
and are described in the "START, STOP, and Other Buttons" section in Chapter
5, " Exam Window Scanning Functions."
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0AS Is~ MRI System Reference Manual TIN hUM llb,pet
Note: Refer to the "Launcher Buttons" section of Chapter 3, ''System Overview, " for a detailed description of menu customization for Launcher too/bar buttons.
Changing the Scan Parameters Area Display Location
The Scan Parameters area can be displayed on the right or left side of the Exam
window. To change the display location, use the following procedure:
I. On the System Settings Launcher button menu, click Window Setting (this
command appears if the System Settings Launcher button menu has been
customized). The Window Setting window opens as shown in figure 6-8.
2. Click the Exam Window tab on the Window Setting window.
3. Click the desired graphical representation for the Scan Parameters area
location. Additionally, the Protocol Properties area can be displayed either
graphically or by task name from this tab as well (figures 6-8 and 6-9).
4. Click OK to save your choices and close the Window Setting window. The
changes made take effect when the next Exam window is opened.
Figure 6-8. The Scan Parameters area on left of Exam window, graphical display of task list (Protocol Properties area) selected.
6-8 Copyright© 2012 by Hitachi Medical Systems America, Inc. All rights reserved.
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Scan Parameters 0
Figure 6-9. The Scan Parameters area on right of Exam window, task name display of task list {Protocol Properties area) selected.
Scan Parameters Descriptions
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The scan parameters are separated into the following sets of related parameters:
Sequence- ! ncludes parameters related to the scan to be performed, such as
slice plane, sequence type, and acquis ition mode.
Seq . Parameter- Includes parameters re lated to pulse sequences (TR, TE, and
NSA) and slices (thickness, interval, and number).
Advanced - Includes parameters related to add itional functions, such as phase
direction, presaturation, and bandwidth.
RADAR (RADial Acquisition Regime)- Includes parameters related to the
sampling of K-space in a radial pattern.
Saturation- Includes parameters related to the suppression of specific s ignals,
such as fat, water, and silicone.
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0AS Is-MRI System Reference Manual YbehtJ ... tlilqHt
Definition: 30 MRA refers to threedimensional magnetic resonance angiography. A slab refers to a collection of slices to be excited with a single excitation pulse, used in 30 acquisitions.
6. 10
T2WPrep (optionai)-A prepulse that enhances the T2 contrast of the imaging
target. When T2WPrep is appl ied to the BASG sequence, tissue contrast
improves but the SNR drops slightly.
MTC (Magnetization Transfer Contrast) - Includes parameters used to change
the contrast of images by moving magnetization from bound protons to free
protons.
VENC (Velocity ENCoding) - Includes parameters related to the use of phase
information to determine the rate and direction of blood flow.
SSP (Sloped Slab Profile) - lncludes parameters related to a sloped slab used to
suppress blood flow saturation in 3D MRA.
MPG (Motion Probing Gradient)- lnc ludes parameters related to scann ing
with the application of a gradient magnetic field to emphasize proton diffusion.
This is used with Diffusion Weighted Imaging (DWI).
Scan Control- Includes parameters related to the tim ing of contrast-enhanced
scans in various scan modes, such as wait t imes, delays, and contrast agents.
RAPID (Rapid Acquisition through a Parallel Imaging Design)- Includes
parameters related to the reduction of phase encode steps, which reduces scan
time.
Gating- Includes parameters used with ECG-, pulse-, and respiratory-gated
scans.
NAVI (NAVIgator Echo) - lncludes parameters related to Nav igator
acquisitions, which are used to reduce a1tifacts produced in a scan region, such
as the heart, where breathing can change the scan position.
PAPE (PA1tial Phase Encode)- Includes parameters related to PAPE, which
improves temporal resolution whi le maintaining image spatial resolution.
F ilter/PostProcessing-Includes parameters related to improving an image's
visual characteristics, as well as other post-processing selections.
Positioning- Includes parameters related to scan position, such as slice order
and plane order.
Others - Includes parameters fo r receiver coils and morning QA functions.
You can change parameter values by selecting from a list of options or by
clicking the up or down arrows (to change a numerical value in a box). You can
also change numerical values by highlighting the value in the box, typing the
new value, and then pressing the ENTER key. Parameters that have a grayed
out appearance are unavailable; th is occurrence depends on the combination
of parameters that have been selected. The Reset button at the top of the Scan
Parameters area resets all parameters to their previously saved default values.
The parameters are described in the remainder of this chapter.
Copyright© 2012 by Hitachi Medical Systems America, Inc. All rights reserved.
Note: The values that can be set may be limited by the Sequence that is selected and related scan parameters.
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Scan Parameters 0 Sequence
The Sequence section of the ScanParameterList window (figure 6-1 0) contains
the fo llowing parameters:
Figure 6-10. The Sequence section of the ScanParameterList window.
Slice Plane - Provides the following options for the plane of the slices, as
shown in figure 6-11:
• AX- Axial
• SAG - Sagittal
• COR-Coronal
• SA-Sagittal and axial
• CA- Coronal and axial
• SC-Sagittal and coronal
• SCA- Sagittal, coronal, and axial
Figure 6-11 . Slice Plane options.
20 /30 - Provides the following options for the acquisition mode, as shown in
figure 6-12:
• I D - One-dimensional acqu isition. Used only in spectroscopy (lD is
automatically selected when Sequence is MRSSE).
• 2 0 - Two-dimensional acquisition. One slice is acquired per TR.
• 3D- Three-dimensional acquisition. ln 3D acquisitions, data encoded with
s lice pos ition information is collected, in addition to phase encoding and
frequency encoding. Multiple slices of image data are reconstructed us ing the
3D Fourier conversion. 30 acquisitions can produce images with varying s lice
thicknesses.
Figure 6-12. Acquisition mode options.
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0AS Is~ MRI System Reference Manual ThehtlentMqiMt
Note: With 30 measurements, the SNR of images is lower at the top and bottom of each slab compared to the center area, making the images susceptible to artifact when using the BASG sequence. Therefore, position the region of interest so that it comes to the center of the slab and set the number of slice encode a little higher.
Note: If homogeneity of the magnetic field is poor, BASG is vulnerable to magnetic field distortion and degraded image quality due to the generation of artifacts. To minimize this effect, be sure to carry out volume shimming before performing the BASG scan.
Note: Slice scan, slab scan, and pre-saturation pulses should be positioned to maximize the TOF effect when scanning with TOF MRA.
Note: If the blood currents often run parallel to scanned slice or slab, if they wind drastically, or if their transit paths substantially differ between the right and left vessels, the MRA image should be carefully interpreted.
Note: Check original images concurrently while interpreting TOFMRA.
6. 12
Sequence-Provides the following options for pulse sequence, as shown in
figure 6-13:
SE (Spin Echo)-Produces images with
proton density, T I, and/or T2 weighting.
• IR (I nversion Recovery) - Uses a 180° inverting radio
frequency (Rf) pulse prior to the 90° excitation pulse to
acquire images with specific suppression.
• GE (Gradient Echo) - Uses a variable flip angle to
acqu ire images with Tl or T2* contrast. The contrast
weighting is primari ly determined by the flip angle .
SE
SE IR GE SARGE RSSG TRSG BASG uTE FSE FIR pnmeFSE pnmeFIR TOF PC SEEPI GEEPI OW EPI RSSGEPI Shim S-Map MRSSE
• SARGE (Steady State Acquisition with Rewound
Gradient Echo) - Uses closely-spaced RF
excitation pulses and short TR (repetition time)
to create a steady-state signal. This sequence
produces images with T I and T2 weighting. Figure 6-13. Pulse Sequence
options.
• RSSG (RF Spoiled SARGE)- Uses closely
spaced RF excitation pulses with variable phase shifts. This sequence
produces images with Tl weighting.
• TRSG (Time Reversed SARGE)- Acquires the signal that was excited by the
prior RF pulse. This sequence produces images with heavy T2 weighting.
• BASG (Balanced SARGE)- Uses a short TR and acquires the signal under a
steady state, with slice-, phase-, and frequency-rewinder pulses. Th is sequence
produces images with high signal-to-noise ratio (SNR), mixed TI /T2 contrast,
and bright fluid.
• FSE (Fast Spin Echo) - Uses multiple 180° RF pulses to more rapidly
produce images with proton density, T l , and/or T2 weighting.
• FIR (Fast Inversion Recovery)- Uses a 180° inverting RF pu lse prior· to the
90° excitation pulse to acquire images with specific tissue suppressions.
• primeFSE- Similar to FSE, except that the user can enter TE and bandwidth
values, rather than values for the Inter E.Time (echo interval) and Echo Shift
parameters (these parameters are described later in this chapter).
• primeFIR-Similar to FlR, except that the user can enter TE and bandwidth
values, rather than Inter E. Time and Echo Shift parameter values.
• TOF (Time of Flight)- Used to produce MRA using flow/ inflow results of
blood.
• PC (Phase Contrast)-Optional. Produces MR ru1giographs using phase
information of blood flow.
Copyright© 2012 by Hitachi Medical Systems America, Inc. All rights reserved.
Note: Image quality with EPI depends largely on the homogeneity of magnetic field. Volume shimming is required before running SE EPI to achieve good image quality.
Note: In the 5-Map sequence, scanning is carried out with the coil used for the mam scan and the TR body coil.
The 5-Map sequence is sensitive to patient movement. Keep the patient as still as possible while S-Map scanning to avoid artifact.
When scanning the abdominal region, breath holds are required in an 5-Map sequence when Mode is Nanna/.
When Wait mode is ON, the system pauses twice: after the prescan and in the middle of the 5-Map sequence.
Tic wide area is to be scanned using the TR body coil. The scanogram should be used with the coil for the main scan. Therefore, make sure that the area which is not scanned through the scanogram does not cause artifact.
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Scan Parameters 0 • SE EPI (Spin Echo using Echo Planar Imag ing)- Produces images with T l
o r T2 weighting using very sh011 acquis ition t imes.
• GE EPI (Gradient Echo using EPI) - Produces images with T2* weighting
using very short acquisition times.
• OW EPI (Diffusion Weighted EPI)- Produces diffusion-weighted images,
which depict the restriction of water molecule diffusion.
• RSSG EPI (RF Spoiled SARGE using EPI)- Optional. Produces images with
Tl weighting using short acquisition times.
• Shim (Shimming)- Performs highly-precise corrections of the static
magnetic field.
• S-Map (Sens itivity Map)- A sequence dedicated to 30 sensitivity map
acquisition. Acquires 30 sensitivity data to be used for shading correction
and RAPID measurement. In this sequence, images (acquired data) are not
displayed.
• MRSSE (MR Spectroscopy using Spin Echo) - Optional. Acquires molecular
dens ities of metaboliz ing substances in the human body.
EchoT ime Mode- Sets the range for the echo time (figure 6-14).
When Sequence is SE, choose one of the following:
• Normal-Use fo r normal scanning.
• Short T E- Use to acquire images with shorter T E than the Normal setting;
however, some parameters such as Dual Slice and Multi Echo will be
restricted.
When Sequence is FSE, FIR, primeFSE, or primeFIR, choose one of the
fol lowing:
• Short! ET- Use to acquire images with short Inter E. Times, such as 12 and
below. In figure 6- 14, Short I ET is selected.
• Longi ET - Use to acquire this s lice images with Inter E.Times of 12 and
above. This selection is used in FIR imaging.
• Optimized- Use to acquire the higher SNR and less aliasing image with
same Inter E.Time as ShortiET. Optimized is avai lable for 3D acquisition
only.
Figure 6-14. The Echo Time Mode scan parameter.
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0AS Is· MRI System Reference Manual n. htJ•t llqJMt
Note: When scanning a patient with an orientation other than feet first supine, the output image has it's orientation rotated, but shimming is not affected.
Note: When scanning with the patient oriented feet first, the output images are in the reverse order of the slice order being set, but shimming is not affected.
6- 14
Mode-Selects the sequence mode.
• Normal - Normal measurement is performed.
• YASC-ASL (optionai) -Creates an image of fluids, such as labeled blood
flow, using a spatial selection lR pulse. When VASC-ASL is selected, IR P ulse is displayed and set to Selective.
• GElR- Performs segment measurement using an IR pulse as a prepulse.
When GEIR is selected, IR Pulse is displayed and set to Segmented. As a
segment becomes larger, contrast may be slightly blurred.
• TIGRE-Performs a high-speed Tl contrast measurement in combination
with a fat suppression pulse for frequency selection. When TIGRE is
selected, Saturation is displayed and set to Segment FS.
• Nest- Collects signals using the receiver coi l and Transmit/Receive Body
coil at nearly the same time during the S-Map sequence. A sensitivity map
not easily affected by movement can be created for regions where movement,
such as breathing, is monitored.
Shim Mode- Provides options for the use of shimming results (figure 6- 15).
• off- Does not use shimming results.
• Volume-Uses volume shimming results. Shimming results are not used
when there are changes in a patient or coils.
• Auto Volume- When measurement conditions include shim measurements,
shimming is automatically performed during prescanning.
• Regional- Performs regional shimming in a specific area designated by the
purple box on the positioning screen. Upon opening a scan task, the regional
sh im box moves along with any movement of the slice group. However, once
the regional shim box is activated, the slice group and regional shim no longer
move together.
A Caution
off Volume AutoVolume ReQ•onal
Figure 6-15. Shim Mode options.
If an error occurs during shimming, contact Hitachi service.
Copyright@ 2012 by Hitachi Medical Systems America, Inc. All rights reserved.
Q54-53287v4
Scan Parameters 0 Additional Notes fo r t be Mode parameter:
The values that can be set may be limited by the selected Sequence and related
scan parameters.
Since GEIR is 3D measurement, the SN R of images is lower at the top and
bottom of each slab compared to the center area. Therefore, position the region
of interest so that it comes to the center of the slab and set the number of slice
encode a little higher.
Pre-saturation pulses may be used with the 30 GEm sequence, however MTC
and FatSat pulses canno t be used.
Additional Notes fo r tbe Sbim Mode parameter:
Estimated fie ld distributions are displayed after volume shimming, however they
are not displayed after regional shimming.
The volume of interest (VOl) must be within the region of volume shimming.
The results of shimming are canceled and become ineffective when the patient
name or receiver coi I is changed, when Shim Mode is off and any measurement
is carried out, or when Prescan is O N and any measurement is carried out.
When Shim Mode is set to anything other than Regional, the VOl is deleted.
The region of shimming, region of imaging, and the direction of phase encoding
shou ld be identical.
The center of shimming should be identical with the center ofthe magnetic field.
Additional Notes for the S-Map pa rameter :
The posit ion and the scan parameters should be set in a way that prevents
aliasing artifact from occun·ing in the area selected fo r the main scan.
Planes to be scanned will vary depending on d1e anatomical region being
scanned. Therefore to avo id a liasing artifact, COR and SAG planes are
recommended because the direction of the body axis is the readout direction.
When setting FOY, it is recommended to set it 20 to 30 percent larger than the
one for the main scan.
S lab thickness should be set according to the size of the region to be scanned,
adjusting S. Encoding.
SNR can be too low when FOV is small. Therefore, it is necessary to ensure
adequate SNR by setting the appropriate NSA.
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0AS Is~ MRI System Reference Manual T'MhtJent MqHt
Note: If performing a Black Blood scan with Multi Slice and Multi Acquisition= 1, adjacent slices are excited in 1 TR, so image quality can be degraded. Perform scans with the slice interval larger than the slice thickness of the Double IR Pulse and STIR Pulse or with Mufti Acquisition ;:: 2.
Note: The values that can be set may be limited by the selected Sequence and related scan parameters.
6. 16
Oblique-Provides methods for determining whether or not scans can be
performed, based on the angulation of slices. Options are (figure 6-16):
• Full -Allows ful l angulation of sl ices, but will require protocol changes if a
steep angle is used.
• Limited- Allows a limited degree of angulation, so that the protocol
paTameters selected for the acquisition can be used.
Seq. Parameter
P!ii limtted Full Limited
Figure 6-16. Oblique methods.
The Seq. Parameter section of the ScanParameterList window (figure 6-17)
contains the following parameters:
Figure 6-17. The Seq. Parameter section of the ScanParameterList window.
FOV- Indicates the size in millimeters ofthe visual fie ld to be reconstructed
fol lowing the scan.
FOV2-Sets the size (in millimeters) of the longitudinal visual field
reconstructed following the scan. The crosswise visual fie ld is set by the FOV
parameter. Used only in spectroscopy (FOV2 is displayed when Sequence is
MRSSE).
TR- Indicates the repetition time in milliseconds of the pulse sequence. During
gated scans, TR values a re automatically set when Trigger is selected for the
Gate or Resp mode.
Copyright© 2012 by Hitachi Medical Systems America, Inc. All rights reserved.
Note: T£2. TE3. and TE4 are used only tor multiple echoes.
Note: Additional/A pulse options (Double, Triple) are associated with the CardioSuite, which is a purchasable option.
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Scan Parameters 0 TE- Indicates the echo period in milliseconds for the first echo. This value is
automatically set when the following are selected from the Sequence list:
• BASG
• FSE
• FIR
• Shim
TE2- Indicates the echo period for the second echo. This setting is displayed
when the selected Sequence is SE, GE, SARGE, RSSG, or FSE, and the
Multi Echo parameter is set to 2 or more. (When FSE is selected, TE2 is
automatically set based on other parameters, such as E.Factor.)
TE3- Indicates the echo time for the th ird echo. This setting is displayed when
the selected Sequence is SE and d1e Multi Echo parameter is set to 3 or more.
TE4- Indicates the echo time for the fourth echo. This setting is displayed
when the selected Sequence is SE and the Multi Echo parameter is set to 4 or
more.
Figure 6-18 shows settings for the TE through TE4 parameters.
~-i . j .. l
Figure 6·18. Example settings for TE, TE2, TE3, and TE4 boxes.
FA (Flip Angle)- The angle of excitation to which the net magnetization is
tipped relative to the main magnetic field.
IR Pulse (Inversion Recovery Pulse)- Indicates if an IR pu lse will be used for
tissue saturation. This is primarily used with Cardiac scanning.
This parameter can be selected when Sequence is SE, BASG, FSE, DW EPI,
SE EPI, or GE EPl.
The following options are available, as shown in figure 6-19:
• Off- Does not perform tissue saturation; this is the recommended setting.
• Single- Perfonns tissue saturation with des ignated T l.
• Double- Executes blood saturation via Double-IR. When Double is selected,
Tl becomes available.
• Triple (optional) - Executes fat saturation via STIR pulse and blood
saturation via Double-JR. When Triple is selected, T l and Tl2 become
available.
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0AS Is~ MRI System Reference Manual T'MhtJent MqHt
Note: Tl and FatSat cannot be combined simultaneously in the STIR type fat suppression.
Note: Optimum T1 of the Black Blood scan varies depending on orientation of the slice plane. When reduction of blood signal is small, modify T1 and retry the scan.
Note: For a FLAIR sequence of the brain, theIR Thk.Ratio should be set to 4.0.
6. 18
• Segmented-Performs segment measurement using the STIR pulse as a
fat suppression prepulse. Segmented is selectable with 3D RSSG (GEIR
imagi11g). When Segmented is selected, TI ru1d Segment become available.
• Se lective-Applies a spatial selection IR pulse. Selective is selectable with
VASC-ASL imaging. When Selective is selected, TI and Segment become
available.
Figure 6-19. Example IR Pulse options.
TI- Sets the Inversion Time, which is the time period between the initial 180° inversion pulse and the 90° excitation pulse in an IR pulse sequence. This box
is available when the selected Sequence is IR or FIR, the ECG Gate Mode is
Delayed or MyoPer, or when IR Pulse is Single. The measurement of the Tl
will be calcu lated as follows:
• W11en Sequence is IR or FIR, or IR P ulse is Single, Tl is the interval
between the STIR pulse and the excitation pulse.
• When Gate Mode is Delayed or MyoPer , Tl is the interval between the STIR
pulse and the zero encode excitation pulse.
• When IR P ulse is Double or Triple, TI is the interval between the Double-IR
pulse and the excitation pulse.
• When IR Pulse is Segmented or Selective, TI is the elapsed time from the
STIR pulse to the zero encoded excitation pulse.
TI2 - Sets the interval (in milliseconds) from the STIR pu lse to the excitation
pulse. Specify a TI2 setting when IR Pulse is Triple.
Segm ent-Sets the number of echoes to be acqu ired after appli cation of one
STIR pulse. Specify a Segment setting when IR Pulse is Triple.
IRFA-Sets the excitation angle (i111 degrees) ofthe IR Pulse spin. Specify an
IRFA setting when Gate Mode is MyoPer.
IR T hk.Ra1io- lndicates the slice thickness selection ofthe in itial 180° pulse
relative to the s lice th ickness of the main scan. The normal setting for this
paramet·er is 1.3. You can use th is pa:rameter when Sequence is FIR or Prime
FIR, or when Sequence is FSE or Prime FSE; and IR Pulse is Single. In figure
6-20, the Sequence is FIR and theIR Thk.Ratio is set to a value of 1.3.
Copyright© 2012 by Hitachi Medical Systems America, Inc. All rights reserved.
Note: The gap between slices can be calculated as. Interval- Thickness = Gap
Q54-53287v4
Scan Parameters 0
Figure 6-20. /R Thk.Ratio example.
BBIR Thk.Ratio - Sets the s lice thickness ratio of the Double-IR Pulse for the
main scan sl ice thickness. Specify a BBJR Tbk.Ratio when Sequence is FSE
or primeFSE and IR Pulse is Double or Triple.
Thickness - Indicates the slice thickness (in millimeters).
Inten ral - lndicates the spacing (in mil limeters) between slices, measured
from the center of one s lice to the center of the next sl ice. The interval in 20
multi-slice acquisitions is between parallel slices; the interval in 3D multi-slab
acqu is itions is betv.-een parallel slabs.
Multi slice- Indicates the number of slices to be acquired during one scan.
Th is setting is displayed for 20 acquisitions on ly.
Multi Echo- Indicates the number of echoes to be collected in one scan. As
the Multi Echo value is increased, additional numbered TE boxes (TE2, TE3,
and so on) become available on the ScanParametcrList window. M ulti Echo is
available when Sequence is SE, FSE, GE, SARGE, or RSSG. In figure 6-21 ,
Sequence is GE and Multi Echo is set to a value of2.
Figure 6-21. Multi Echo example.
6. 19
0AS Is-MRI System Reference Manual YbehtJ ... tlilqHt
6 • .20
Multi slab- Available for 3D acquisitions only. Indicates the number of slice
slabs to be acqu ired in one scan. In figure 6-22, Sequence is TOF and Multi
slab is set to a va lue of 4.
Figure 6-22. Multi slab example.
Recon P itch - A llows the desired thickness of the reconstructed slices to be
input. Recon P itch can be a value no less than one-half of the acquired slice
thickness (the Thickness parameter).
Recon Pitch will automatically adjust to maintain the ratio between T hickness
and Recon Pitch values. Additionally, Recon Pitch automatically reverts to
upper and lower lim its when an entered value exceeds e ither limit (the upper
limit is Thickness, and the lower limit is one-half of Thickness).
Recon Slice- The number of slices to be reconstructed for the acquisition.
Slice Reject[% ]- lndicates a percentage of sl ices at the slab ends that wi ll not
be reconstructed. This is useful for 3D acquisitions that may have decreased
SNR at the slab ends. One half of the value that is selected is rejected fi·om each
end of the slab (for example, if20 percent is selected, 10 percent of the total slab
will be rejected from each end).
Overlap[% J- Indicates a percentage amount of slab overlap, which is used
to improve the signal continuity between s lab intervals in 3D TOF multi-slab
acquisitions. The Multi slab parameter must have a value greater than I.
Copyright© 2012 by Hitachi Medical Systems America, Inc. All rights reserved.
Q54-53287v4
Scan Parameters 0 Figure 6-23 shows the Slice#, Slice Reject [%], and Overlap[% ] parameters set
for a 3D TOF series.
Figure 6-23. Slice#, Slice Reject[%], and Overlap[%] example.
Multi Acquisition- Indicates the number of acquis itions. This setting is
available when the Mode parameter is Interleaved or Sequentia l.
When Mode is Stack, the value in M ulti Acquisition is unavailable, but wi ll be
the same as the value set in the Stacks box, as shown in figure 6-24.
"' • Figure 6-24. Multi Acquisition example.
When the M ode parameter is SingleSiice, M ulti Acquisition is unavai lable.
However, the displayed number of acquisitions will be the same as the number
set in M ulti slice for 2D acquisitions, or the number set in Multi slab for 3D
acquisitions, as shown in figure 6-25.
Multi slice
-~ l@ft#iiijli!Fii* 5
Multi slab
Figure 6-25. SingleS/ice Mode examples for 20 and 30 acquisitions.
The following examples explain how the M ulti Acquisition, Mode, and
Multi slice parameters can be set in various combinations to acquire images
differently.
Example 1: M ulti slice is 6, Mode is Interleaved, and M ulti Acquis ition is 2.
The value of2 in the Multi Acquis ition box divides the slices into two groups
of three s lices each. The Interleaved mode acquires the top and bottom s lices,
then the middle slice in each group, all with the same TR. For these parameter
settings, the first acquisition would be slices I and 3, and then slice 2; the second
acquis ition would be slices 4 and 6, and then slice 5.
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0AS Is-MRI System Reference Manual YbehtJ ... tlilqHt
6 . .2.2
Example 2: M ulti Slice is 6, Mode is Sequential, and M ulti Acquisition is 2.
The value of2 in the M ulti Acquisition box divides the sl ices into two groups
of three slices each. The Sequential mode acqu ires the slices in numerical order,
one group at a time, all with the same TR. For these parameter settings, the first
acquisition would be slices I, 2, and 3; the second acquisition wou ld be slices 4,
5, and 6.
Example 3: M ulti Slice is 6, Stacks is 2, and Mode is Stack.
Stack mode can be used when slices are set at different angles, such as in axial
lumbar imaging. Stack mode acquires the slices in the first stack, then the slices
in the second stack, all with the same TR. For these parameter settings, the
setting of the Stacks value at 2 with Mode set to Stack causes the M ulti Slice
box to be updated and disp lay a total of 12 slices (6 slices x 2 stacks= 12 total
slices).
Example 4: M ulti Slice is 6 and Mode is SingleSlice.
SingleSiice mode is used to acquire one slice per TR, as in 20 TOF sequences.
For these parameter settings, each slice (of the 6 total slices) will be acquired
individually.
Mode-Specifies the acquisition mode. The options, as shown in figure 6-26,
are:
• Interleaved -Slices are acquired in an odd- and even-numbered fashion (such
as slice numbers 1, 3, 5, 7, then slice numbers 2, 4, 6, 8).
• Sequentia l-Slices are acquired in order of sl ice number (such as 1, 2, 3, 4).
• Stack-Slices are acquired for each angle.
• SingleSlice-Each slice is acquired as a separate acquisition, with the
selected parameters (one slice per TR).
"!¥'
Figure 6-26. Mode options.
Copyright© 2012 by Hitachi Medical Systems America, Inc. All rights reserved.
Q54-53287v4
Scan Parameters 0 Slice#- Indicates the number of slices to be reconstructed for 3D acquisitions
(figure 6-27).
Figure 6-27. Slice# example.
Stacks- Indicates the number of groups when acqu iring multiple groups with
different angles.
Freq#- lndicates rhe number of sampl ing steps in the frequency axis, as shown
in figure 6-28. Hold the mouse pointer over the Freq# box to view the range that
is available.
IM §s6 ::J .. ' ..
Figure 6-28. The Freq# parameter.
Phase# - Indicates the number of sampling steps in the phase axis, as shown in
figure 6-29. Hold the mouse pointer over the P hase# box to view the range that
is available.
Figure 6-29. The Phase# parameter.
Freq Point- Sets the frequency resolution. Used only in spectroscopy (Freq
Point is displayed when Sequence is MRSSE).
ReconMatrix - lndicates the reconstruction matrix for the image. A value
larger than the frequency encoding value (from the Freq# box) and/or the
phase encoding value (from the Phase# box) can be set. Figure 6-30 shows
ReconMatrix options.
'*'""" "-=5:..;.;12=-------f 128 256 512 1024 2048
Figure 6-30. ReconMatrix options.
6· 23
0AS Is~ MRI System Reference Manual T'MhtJent MqHt
Note: A value must be entered in the APR[%} box to make Half Scan available.
NSA (Number of Signals Averaged)- Indicates the number of s ignal
acquisitions to be averaged. Increasing NSA will improve the SNR ofthe image,
but also increases scan time. Doubling NSA doubles the scan time, but only
increases the SNR by approximate ly 40% because increased noise accompanies
the increased number of signals.
APR[%] (Asymmetric Projection Rate)- lndicates a percentage ofK-space
that w ill not be acquired in the phase encoding d irection. K-space as a whole is
I 00%; the APR[%J parameter can be set to values between 0% and 45% and
can be changed by 5% intervals. This parameter is used in conjunction w ith
Half Scan.
The position of the non acquired K-space region changes for each of the echo
layouts, as shown in figure 6-31. In addition, processing of the non acquired
region c hanges according to the setting of the Half Scan parameter (described
next in this section).
Frequency Frequency Frequency Frequency
PhaseW 4 PhaseW 1 PhaseF 1 Phase~ 5
6-24
3 2 2 4 2 3 3 3 1 4 2 1 4 1
APR APR APR APR
Centnc Ant1 Centnc Sequential ADA
Slice
Phaser, APR
Slice
Phaser, 1 3 2
1 3 2 4 6 5
4 6 5 7 9 8
8 7 9 11 10 12
11 10 12 APR
PEAKS RPEAKS
Figure 6·31. K-space filling for various echo layouts.
Half Scan -Enables image acquisition in a sha tter time by limiting the
sampling of the phase axis inK-space. Spatial resolution is maintained, but
SNR is reduced. Images are created using the acquired data, combined with the
interpo lated data used to fi II the non acquired region of K-space. Acquisitions
are performed in accordance with the val ues set for the phase direction in the
APR[%] parameter. The options, as shown in figure 6-32, are:
Copyright@ 2012 by Hitachi Medical Systems America, Inc. All rights reserved.
Note: OW/ is sensitive to movement smce the MPG pulse is applied. In multi-shot measurements, use gated scanning with the scan region immobilized to reduce motion artifacts.
Q54-53287v4
Scan Parameters 0 • off-Does not use Half Scan.
• ON-Uses Half Scan.
"'""' off ·~ off ON
Figure 6-32. K-space filling for various echo layouts.
The following examples explain how the APR(%} and Half Scan parameters
function together:
Example 1: APR(%] set at 25 percent and Half Scan is ON (figure 6-33)
This is the equivalent of~ Scan. Data is acquired from three-foUJths (~)or 75% of K-space; one-foUJth ('.!.!)or 25% of K-space is interpolated.
:1*'1'111[5 :J .. €MIA*'' ( ON ·I
Figure 6-33. The equivalent of three-quarter scan.
Example 2: APR(%] set at 45 percent and Half Scan is ON (figure 6-34)
This is the equivalent of 1/ 2 Scan. Data is acquired from 55% of K-space; 45% of
K-space is interpolated.
1'1''1'1111~~45=-~~---IMIP*ii I ON • )
Figure 6-34. The equivalent of one-half scan.
Shot Num.- Indicates the number of RF excitations, or TR periods, needed to
acquire data, as shown in figure 6-35. A lower shot number results in a faster
scan time. The shot number can be calculated using the fo llowing equation:
Phase# "'" E. Factor = Shot Num.
Figure 6-35. Shot Num. example.
Shot Num. is available when Sequence is SE EPl, DW EPL or GE EPI. Hold
the mouse pointer over the Shot Num. list to display the range of settings.
6· 25
0AS Is-MRI System Reference Manual YbehtJ ... tlilqHt
Note: When Echo A/foe. is Centric and if# RF Prep is extremely small, good images cannot be obtained since data acquisition starts while steady state has not yet been reached.
6 • .26
Shot Num. is displayed, but unavai lable, in the following cases:
• Sequence is FSE, FIR, RSSG or EPI.
• Sequence is Prime FSE or Prime FIR, and Echo Alloc. is Centric.
E.Factor - The number of echoes to be used to create a s ingle image. An
acceleration rate is obtained based on the number of echoes used. However, the more the echo is delayed, the weaker the signa l strength becomes due to the decay of signal amplitude (T2 or T2*). As the E.Factor increases, the SNR and
resolution decrease.
E.Factor is avai lable when Sequence is FSE, FIR, or RSSG EPJ.
E.Factor is displayed but unavailable in the following cases:
• Sequence is SE EPI, DW EPI, or GE EPI.
OR
• Sequence is P rime FSE or Prime FIR, and Echo Alloc. is ADA.
Inter E. Time- The time between echoes. Inter E.Time is displayed when
Sequence is any of the following: FSE, FIR, SE EPI, DW EPI, GE EPI, or RSSG EPI. When Sequence is FSE or FIR, an effective TE is calcu lated by the system. This TE calculation inc ludes the E.Factor, Echo Alloc., Echo Shift, and Inter E. Time parameters to determine image weighting.
Echo Shift-Adjusts image contrast by changing the location of the effective TE in K-space, without changing the number of echoes. An Echo Shift of 1
changes the effective TE by an increment equa l to the value displayed in Inter E. Time. Echo Shift is available when Sequence is FSE, FIR, SE EPI, GE EPI, RSSG EPI, or DW EPI. Echo Shift is displayed but unavailable when
Sequence is Prime FSE or Prime FIR.
Echo Shift2 - AIIows Echo Shift to be selected for the second echo. Echo Shift2 is available when Sequence is Prime FSE or Prime FIR.
Echo Alloc. - AIIows the echo layout method to be selected. A pa11ial listing of options is shown in figure 6-36.
The options are:
• Sequential
• Centric
• AntiCentric
Centric Ant1Centnc
Figure 6-36. Echo A/foe. options.
Copyright© 2012 by Hitachi Medical Systems America, Inc. All rights reserved.
Q54-53287v4
Scan Parameters 0 • ADA (Asymmetric Data Allocation)
• PEAKS (optional)
• RPEAKS (optional)
• TPEAKS (optional)
• Seq-Seq (optional)
• Cent-Cent (optional)
• Cent-Seq (optional)
Sequence determines which Echo Alloc. options are available. Sequential, Centric, AntiCentric, and ADA are frequency/phase 2D echo layouts (figure
6-37).
The non acqu ired reg ion will be determined in combination with the value set in
the APR[% 1 parameter. Processing of the non acquired region will change
according to the Half Scan paramete r value. For example, Half Scan is
automatically set when ADA is selected.
Frequency
PhasefC 4
Frequency
PhaseW 1
Frequency
Phase.fe 1
Frequency
PhaseW 8 3 2 2 7 2 3 3 6 1 4 4 5 1 4 5 4 2 3 6 3 3 2 7 2 4 1 8 1
Centnc Ant1 Centnc Sequential ADA
Figure 6-37. Frequency/phase 20 echo layouts.
PEAKS and RPEAKS are optional phase/s lice 2D echo layouts (figure 6-38),
wh ich are used during 30 contrast-enhanced MRA. Acquisition is started
in the direction of the epicenter of K-space. When the epicenter is acquired,
acquisition is pe1formed receding from the epicenter. When the APR[%] parameter is 0, there is no difference between PEAKS and RPEAKS. However,
when the APR I% J parameter is set to anything above 0, the non acquisition
reg ion d iffers. Processing of the non acquired region changes according to the
Ha lf Scan parameter value.
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0AS Is-MRI System Reference Manual YbehtJ ... tlilqHt
6 . .28
Slice
Phaser,
1
4
8
11
APR 3 2
6 5
7 9
10 12
PEAKS
Slice
Phaser, 1
4
7
11
3 2
6 5
9 8
10 12
APR
RPEAKS
Figure 6-38. PEAKS and RPEAKS optional phase/slice 20 echo layouts.
TPEAKS is an optional phase/slice 2D echo layout, which is used during 3D contrast-enhanced MRA in the same way as PEAKS and RPEAKS. The
distance between the center of the phase/slice plane and each acquisition point is
used as the standard to set the acquisition order. As shown in figure 6-39,
acquisition is performed from the center of the phase/slice plane, with the time
that K-space data collection begins as the peak of the contrast agent density.
Acquisition is then performed on the side closest to the center.
Slice
Phaser,--------------~
4
Figure 6-39. TPEAKS optional phase/slice 20 echo layout.
Seq-Seq is selectable on ly with 3D RSSG (GEJR imaging). The measurement
order of both phase encode and slice encode is Sequential. With Seq-Seq, temporal efficiency is better than Cent-Seq and Cent-Cent since data is
acquired before the Tl time.
Cent-Cent is used with 30 RSSG (GEIR) or TIGRE imaging. Echo allocation
for both the phase and slice encode directions is Centric. When using this echo
allocation, #RF Prep must be increased. However, increasing #RF Prep results
in the reduction of fat suppression by the FatSat pulse.
Copyright© 2012 by Hitachi Medical Systems America, Inc. All rights reserved.
Q54-53287v4
Scan Parameters 0 Cent-Seq is an echo allocation option for TIGRE imaging. Echo allocation for
the phase encode direction is Centric, while the echo al location for the sl ice
encode direction is Sequentia l. Centric scans from the center of K-space toward
the peripheral region, while Sequential scans from the peripheral region toward
the center, sequentially.
Figure 6-40 illustrates the Seq-Seq, Cent-Cent, and Cent-Seq echo allocation
options.
I
I
1
2
3
4
5
Seq-Seq
Q) '0
8 c: w
~ t Q.
4 3
r---1 2
Slice Encode
I I
3 2
1
1 2
3
Cent-Seq
Q)
8 c: w
~ t Q.
l
-3 2
1
I
3 2
1
1
2
3
Cent-Cent
4
Slice Encode
---'1 1
2 3
Slice Encode
Figure 6-40. Seq-Seq, Cent-Cent, and Cent-Seq echo allocation options.
3D Acq. Mode-Selects the measurement field of the ky-kz plane (K-space), as
shown in figure 6-41.
II II II C1rcular · I Normal I C1rcular I ... ~
Figure 6-41. 3D Acq. Mode options.
6· 29
0AS Is-MRI System Reference Manual YbehtJ ... tlilqHt
6-30
• Normal - Measures the rectangular field in the ky-kz plane (figure 6-42), when
Cent-Cent or Cent-Seq echo allocations are used with TIGRE.
-.ky Normal
Figure 6-42. Norma/3D Acq. Mode K-space measurement field concept.
• Circular - Measures the inscribed circle in the rectangular fie ld of the ky-kz
plane (figure 6-43), when the Sequence parameter is RSSG and the Mode
parameter is TIGRE.
kz
I __..v 1""---
I t'\
\. v .......
1""--- v /
-.ky Circular
Figure 6-43. Circular 3D Acq. Mode K-space measurement field concept.
Chemical Shift- Indicates the optimum polarity ofthe phase-encoding
grad ient magnetic field. The po larity can be changed to minimize the effects
of image distortion. C hemical Shift is available when Sequence is SE EPI,
GE EPI, DW EPI, or RSSG EPI, and Echo Alloc. is Sequentia l or ADA. As
shown in figure 6-44, the options are:
• Normal -Normal polarity of the phase encoding gradient magnetic field.
• Reverse- Reverse polarity of the phase encoding gradient magnetic field.
Normal
Normal Reverse
Figure 6-44. Chemical Shift options.
Copyright© 2012 by Hitachi Medical Systems America, Inc. All rights reserved.
Note: The values that can be set may be limited by the selected Sequence and related scan parameters.
Q54-53287v4
Scan Parameters 0 DE Pulse (Driven Equi librium Pulse)-An additiona l pulse that can be used
fo llowing s ignal collection to possibly decrease TR and consequently decrease
scan time, while maintaining T2 contrast. A DE pulse converges the transverse
relaxation of the magnetization and forces it to longitudina l relaxation. DE
Pulse is available when Sequence is FSE, FIR, P rime FSE, or Prime FlR. The
following options are available, as shown in figure 6-45:
• off-Does not add the DE pulse.
• ON-Adds the DE pulse.
II++ off ~ I I off ON
Figure 6-45. DE Pulse options.
M ulti Voxei- Indicates the number ofvoxels acqui red in one scan. Used only
in spectroscopy (M ulti Voxel is displayed only when Sequence is MRSSE).
Advanced
The Advanced section of the ScanParameterList window (figure 6-46)
contains many additional parameters that can be used during image acquisitions.
Figure 6-46. The Advanced section of the ScanParameterLfst window.
P resat (Presaturation)-AIIows presaturation pulses to be applied that can
reduce artifacts by control ling the signals from movable areas (such as blood
flow signal or the abdominal wall).
Presaturation is a technique that uses repeated RF excitation of structures
adjacent to the anatomy of interest to reduce or e liminate the phase effect
artifacts that can be caused by flowing nuclei in these adjacent structures. The
signal from the flowing nuclei is saturated, and therefore llullified, upon entering
the FOV.
6. 31
0AS Is~ MRI System Reference Manual nt.hU•tMqJMt
Note: Refer to chapter 3-2 of the Oasis How-to Manual for complete presaturation pulse details.
6-32
You can set a maximum of eight presats, with the Presat box displaying the total
number. The first two presats are automatically set as parallel regions adjacent to
the sl ice surface. These two regions prevent the blood flow signal from flowing
into the slice plane to be scanned. Presats are displayed in blue. The mouse can
be used to rotate, move, or magnify the presat regions.
Normal - Applies presats for each slice acqu isition. Figure 6-46a shows a
normal presat.
Figure 6-46a. A Normal presat.
Copyright© 2012 by Hitachi Medical Systems America, Inc. All rights reserved.
Q54-53287v4
Scan Parameters 0 Walking -Allows the position of the presat region to move, or "walk," for
each s lice acquired (or each slab in 30). In this manner, the presat always
remains adjacent to the slice. This is used when acquiring blood vessel images
in angiography.
Walking is available when Sequence is TOF or BASG. If a wa lking presat is
selected, it is the first presat d isplayed in the viewport, and it is d isplayed in
green. On ly one walking presat is avai lable. The mouse can be used to rotate,
move, or magnifY the walking presat region . The number displayed in the
P resat box is the total number of presats, including the walking presat. Figure
6-47 shows a walking presat.
Figure 6-47. A Walking presat.
Intermittent- Applies presats for each repetition time (which is the va lue set
in the TR parameter): normally, the presat is applied for each sl ice acquisition.
Intermittent presats will allow you to increase the number of slices; however as
the TR increases, the effectiveness of the presat decreases.
The max imum number of intermittent presats available is 2. The intermittent
presats will be displayed in light blue. The mouse can be used to rotate, move,
or magnify the intermittent presats. The number displayed in the P resat box is
the total number ofpresats, including the intennittent presats.
Figures 6-48 and 6-49 show the Inte rmittent parameter with values of I and 2
respectively.
6-33
0AS Is~ MRI System Reference Manual 11141 htlet~t olllqHt
6-34
Figure 6-48. Intermittent set to 1.
Figure 6-49. Intermittent set to 2.
Segment - May improve presat resu lts. Available when Sequence is BASG, and
one or more presats have been selected. Figure 6-50 shows Segment set to l.
Figure 6-50. The Segment parameter.
Copyright© 2012 by Hitachi Medical Systems America, Inc. All rights reserved.
QS4-53287v4
Scan Parameters 0 Dual Slice-Acquires twice as many images with the same scan parameters
by acquiring two parallel slices at a time. The number that can be entered in the
M ulti slice box is doubled. An even number is required in the NSA parameter
box. Dual Slice is available when Sequence is SE, IR, or GE. The options for
Dual Slice, as shown in figure 6-51 , are:
• off-Does not use dual slice.
• ON -Uses dual s lice.
l'.i@II!EIIIII~Jo~ff------~·1 ~N I
Figure 6-51. Dual Slice options.
Rephase (Flow Compensation) - Used to suppress flow artifacts, such as blood
and CSF. The options, as shown in figu re 6-52, include:
• off-No rephase.
• Slice- Rephase is applied along the sl ice direction only.
• Freq- Rephase is applied along the frequency direction only.
• Slice_Freq- Rephase is applied along the slice and frequency directions.
off off Shce Freq Shce Freq
Figure 6-52. Rephase options.
The available Rephase options depend on the selected Sequence. For multi
echo acquisitions, the presence or absence of Rephase for each echo is as
follows:
Sequence 1 Echo 2 Echoes
SE No rephase Rephase
GE Rephase Rephase
SARG E Rephase Rephase
RSSG Rephase Rephase
FSE Rephase Rephase
primeFSE Rephase Rephase
6· 35
0AS/S~ MRI System Reference Manual n.ratJentlll.q:net
Note: As the frequency bandwidth of the reception signal is reduced, the SNR of the image increases. However, chemical shift artifacts (a phenomena where the difference in the resonance frequencies between water and fat diverge on the image) will become noticeable.
6-36
Bandwidth[kHz]-lndicates the frequency bandwidth (kHz) ofthe reception
signal, as shown in figure 6-53. Since noise is distributed evenly across a ll
frequency bandwidthsj reducing the frequency bandwidth value reduces noise
and improves the SNR; however, chemical shift artifacts may become more
noticeable.
Figure 6-53. The Bandwidth[kHz] parameter.
Bandwidth2[kHz]- Indicat es the frequency bandwidth (kHz) of the reception
signal for the second and subsequent echoes during a multi-echo acquisition.
This parameter is available when Sequenc~ is SE, GE, SARGE, or RSSG, and
Multi Echo (under Seq. Parameter) is 2 or more.
In figure 6-54, M ulti Echo is set to 2, and Bandwidth2[kHz] is set to I 0.
04 17 1 1m3 ..
Figure 6-54. A Bandwidth2[kHz] parameter example.
Copyright© 2012 by Hitachi Medical Systems America, Inc. All rights reserved.
Note: The larger the AMI[%] value, the shorter the TE. However, if Half Echo is off, there may be a degradation of spatial resolution.
Note: Half Echo uses frequency direction data in the same manner that Half Scan uses phase direction data.
Q54-53287v4
Scan Parameters 0 AMII %1 (Asymmetric Measurement Imaging)- Indicates the percentage
(usually 20% to 30%) of the early portion of the echo signal that wi ll not be
measured, as there is more noise in the beginning of the echo signal (as shown
in figure 6-55). Asymmetric measurement imaging allows the user to shor1en the
TE and increase the number of slices, and may result in improved contrast on
T l-weighted images. However, if AMI[%) is set to 30% or higher without
setting Half Echo to ON, spatial resolution may be degraded (Half Echo is
described next in this section).
_j: 100% ~ ; Frequency ~ . ~ d
. t" GC Asymmetnc measurem nt rrec ron imaging (%)
L Echo signa1---_J
Figure 6-55. AMI[%] illustration.
Half Echo- Prevents degradation of spatial resolution during AMI[%].
Half Echo creates an image by estimating the uncollected data (based on the
collected data) in the frequency direction. It allows for the use of a shor1er TE,
or lower bandwidth. The options are:
• off- Does not use half echo.
• ON- Uses half echo.
Echo Type- Indicates the echo allocation method. and is fixed as Half.
Used only in spectroscopy (Half is automatical ly selected when Sequence is
MRSSE).
Rect.FOV (Rectangu lar Field ofView)- Reduces the number of acquisition
points in the phase direction (set in the Phase# parameter). R ect.FOV is used to
match the size of the phase encod ing direction for the scan target, as well as for
the FOV that has been set.
The scan time will be reduced by the amount that the va lue of P hase# is
reduced. Although dle spatia l resolution is the san1e as for a normal scan, the
SNR wi ll be reduced in accordance with the number of reductions in the phase
encoding d irection.
6·37
0AS Is~ MRI System Reference Manual T'MhtJent MqHt
6-38
As shown in figure 6-56, the options inc lude:
• off- Does not use Rect.FOV.
• Auto-Acquires the size of the patient in the phase encoding direction, and
then automatically determines the fOY actually acquired and the number of
acquisition points in the phase direction.
• Manual- Allows the user to select the size of the rectangular FOV.
off Auto Manual
Figure 6-56. Rect.FOV options.
Size[%] - Available when Rect.FOV is Manual. Allows you to enter the size
of the rectangular FOV to be acquired; this value is displayed as a percentage of
the current FOV parameter (under Seq. Parameter). Figure 6-57 shows
Size[%] set to 80, meaning the FOY will be reduced by 20% in the phase
encoding direction.
Figure 6-57. Size[%] example.
Anti.aliasing- Removes a liasing artifacts that are produced when the patient
is larger than the FOY in the phase encoding direction. Anti-aliasing is also
effective in reducing motion artifacts in certain anatomic regions (such as the
chest or abdomen).
As shown in figure 6-58, the options include:
• off-Does not use anti-aliasing.
• Auto- Acquires the size of the patient in the phase encoding direction. The
FOV that is actua11y acquired and the number of acquisition points in the
phase direction are automatically determined based on the value of the Mode
parameter, which is described next in this section. The available Mode options
are Res and Time.
• Manual- Allows the FOV size to be entered in the Size[% ] box. The
available Mode options are Res, T ime, and TimeRes.
off
off Auto Manual
Figure 6-58. Anti.aliasing options.
Copyright© 2012 by Hitachi Medical Systems America, Inc. All rights reserved.
Note: If# RF Prep is set to an extremely low value, data with large signal variations will be acquired. causing artifact.
054·53287v4
Scan Parameters 0 Mode-Specifies the manner in which anti-aliasing is perfonned: maintaining
spatial resolution, maintaining scan time, or both. The following options are
always available:
• Res- Spatial Resolution Mode. Increases the number of acquisition points
in the phase direction according to the value of the Size I% I parameter. The
spatial resolution is maintained, but the scan time increases based on the value
of the SizcJ% 1 parameter.
• Time-Scan Time Mode. Increases the acquisition FOV according to the
value ofthe Size[% ] parameter, but does not change the number of acquisition
points in the phase direction. The scan time is maintained, but the spatial
resolution decreases based on the value of the Size[%] parameter.
The following additiona l option is available when Aoti.aliasing is Manual:
• TimeRes-Scan Time/Spatial Resolution Mode. Doubles the number of
acq uisition points in the phase direction and reduces the effective NSA by
half. The NSA parameter must be set to an even number. The SNR, scan time,
and spatial resolution are all maintained.
Figure 6-59 shows the Mode options.
lilllll I Auto I .::11111111 I Manual ·I .
'' [Res · ] WI ~Res ·) Res I Res I Time T1me
TimeRes
(a) (b)
Figure 6-59. Mode options when Antl.aliaslng is Auto (a) and Manual (b).
Size[% ] - Tndicates the size ofthe FOY that is measured when Anti.aliasing is
Manual. This number represents a percentage of the number entered in the
FOV parameter (under Seq. Parameter). If Mode is TimeRes, Size[% ]
defaults to 200. Figure 6-60 shows the Size[% ] parameter set to 150.
Figure 6-60. Size[%] parameter option.
# RF P rep-Allows you to enter the number of reserve RF excitations prior to
scanning. This value can affect both image contrast and artifacts.# RF Prep is
avai lable when Sequence is BASG.
DummyEcho- AIIows the short TE s ignal component to be skipped when
acqu iring heavi ly T2-weighted images. DummyEcho is available when
Sequence is Prime FSE or Prime Fm.
6· 39
0AS Is~ MRI System Reference Manual T'MhtJen.t MqMt
6-40
NaviEcho - Determines if the navigation echo used for compensation is
acquired. NaviEcho is automatical ly set to ON when Sequence is DW EPI and
Shot Num. is 2 or more.
• off- The navigation echo is acquired .
• ON- The navigation echo is acquired and compensation is implemented.
RF P hase- Allows you to enter the phase angle of the RF pulse when the RF
pulse is used to control the previous excitation s ignal. The un it is degrees. RF Phase is available when Sequence is BASG or PBSG. RF P hase is displayed
but unavailable when Sequence is RSSG, TOF, PC, or RSSG EPI.
Figure 6-61 shows that Sequence is BASG, with# RF Prep set to 37 and RF
Phase set to 11 7.
o4 44 s lii:!:II EIII
Figure 6-61. RF Phase parameter example.
P hase D ilr. A- Specifies the phase encod ing direction for t he axial (AX) plane.
Phase Dilr. A is available when Slice Plane is AX, SA, CA, or SCA. As shown
in figure 6-62, the options are:
• A-P- Sets the phase encoding direction as Anterior-Posterior.
• R-L- Sets the phase encoding direction as Right-Left.
Figure 6-62. Phase Oir. A options.
Copyright© 2012 by Hitachi Medical Systems America, Inc. All rights reserved.
Note: More echoes need to be acquired to fill the measurement space in order to acquire images with the same spatial resolution as~atofNonnaiScan. Th~
results in a longer scan time than that of Nonnal Scan.
Note: If chemical shift occurs when using RADAR, the fat in the image may be blurred ..
QS4-53287v4
Scan Parameters 0 Phase Dir. S-Specifies the phase encoding direction for the sagittal (SAG)
plane. P hase Dir. Sis available when Slice Plane is SAG, SA, SC, or SCA. As
shown in figure 6-63, the options are:
• A-P- Sets the phase encoding direction as Anterior-Posterior.
• H-F - Sets the phase encoding direction as Head-Foot.
Figure 6-63. Phase Dir. S options.
Phase Dir. C - Specifies the phase encoding direction for the coronal (COR)
plane. Phase Dir. Cis avai lable when Slice P lane is COR, CA, SC, or SCA. As
shown in figure 6-64, the options are:
• R-L-Sets the phase encoding direction as Right-Left.
• H-F - Sets the phase encoding direction as Head-Foot.
RADAR
IQ144Q!I ~R-L R-L 1-1-F
Figure 6-64. Phase Dir. C options.
RADAR (RADial Acquisition Regime) is a nonorthogonal sampling scan
function, which samples K-space in a radial pattern. It is used to reduce motion
artifacts.
The RADAR section of the ScanParameterList window (figure 6-65) contains
the following parameters:
Figure 6-65. The RADAR section of the ScanParameterList window.
A Caution RADAR can create artifacts in the tangential and circumferential directions,
unlike artifacts that may occur with conventional scan methods. Care should be
taken to avoid a potential misdiagnosis.
RADAR- Specifies whether the RADAR function is ON or off. RADAR can
be used when Sequence is FSE, FIR, primeFSE, primeFffi, SE, or BASG.
0AS Is-MRI System Reference Manual YbehtJ ... tlilqHt
Note: If homogeneity of the magnetic field is poor, FatSat is vulnerable to magnetic field distortion and the fat suppression effect is lowered due to the generation of artifacts. Therefore, be sure to carry out volume shimming
FfJPJ~ performing FatSat.
Blade refers to a segmented area that rotates in the measurement space.
Phase
6-42
Mode-Specifies measurement mode. As shown in figure 6-66, the options are:
• Res - Scan time increases while resolution is maintained.
• Time-Scan time is maintained and resolution decreases.
Figure 6-66. Mode options.
Proj#- Displays the total number of acquired echoes. Proj# is set
automatically, according to the value of Phase# (under Seq. Parameter).
E . Factor-Sets the number of echoes acquired per Blade. As E . Factor
increases, scan time decreases.
Blade-Displays the number of Blades used in the RADAR acquisition. The
system automatica lly calcu lates and displays the number of Blades, based on the
values of the Proj.# and E. Factor parameters. Blade approximates the Proj.#
value divided by the E. Factor value (Blade = Proj.# + E. Factor).
Figure 6-67 shows the relationship between Blade and E. Factor values.
Blade Phase
Figure 6-67. The relationship between Blade and E. Factor values.
Block- Indicates the number of partitions for the entire scan. Block is avai lable
when Sequence is BASG and Saturation is FatSat, or when Sequence is
BASG and Gating is anything but off.
Segment- Indicates the number of segments per FatSat pulse. Segment is
automatically calcu lated by the system using the val ues in the E.Factor, Blade,
and Block boxes as fo llows:
Segment = (Blade x E .Factor) +Block
Copyright©2012 by Hitachi Medical Systems America, Inc. All rights reserved.
Note: When STIR-type fat suppression is carried out using Tl time. do not set Saturation to FatSat.
Note: If you have not set a TR value that makes the phases for water and fat opposite (around 6.8{ms]) when Saturation is PhaseCycle, the fat suppression results may be insufficient.
QS4-53287v4
Scan Parameters 0 Saturation
The Saturation section of the ScanPat·ameterList window contains the
fo llowing parameters:
Satura tion-Provides the fo llowing options for suppressing specific signals, as
shown in figure 6-68:
• off-Does not perform signal suppression.
• FatSat- Suppresses MR signals produced by fat e lements by eliminating
specific RF waves. Clicking FatSat from the Saturation list a lso displays the
Wave, Duration, and RF amp.[%] parameters. The maximum number that
can be set in the M ulti slice box (in the Seq. Parameter area) may be reduced
ifTR is to be maintained. In addition, the SNR may decrease and contrast may
change, depending on the settings for the Duration and Off.Freq parameters.
• Segment FS-Segmented fatsat pulse used with TIGRE sequences to
maintain fat suppression in dynamic scans.
• PhaseCycle -Scanning is performed multiple times and fat signals are
selectively suppressed. M ulti scan mode (in the Scan Cont rol area) must be
set to F luoro or Dyna mic and Sequence must be BASG.
• Water Excitation- Water magnetization is selectively excited and fat
magnetization is suppressed. Sma ller composite pu lses (that add up to 90
degrees) are used; only water protons are fl ipped to the transverse plane and
can emit a signal.
• Water Saturation-Particular RF waves are irradiated to suppress MR signals emitted from water. Used only in spectroscopy (Water Saturation is
automatically selected when Sequence is MRSSE).
•w!Fi•
[A Caution
off
off FatSat Phase Cycle Water ExcJtabon
~·-·m•liiliilll off · )
I ~:tSat SegmentFS Water Excrtabon
Figure 6-68. Saturation options.
Be sure to carry out shimming before starting a water excitation measurement.
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0AS Is-MRI System Reference Manual YbehtJ ... tlilqHt
Definition: Precession refers to the secondary spin of hydrogen nuclei when placed within a magnetic field.
6. 44
Additional Parameters when FatSat is selected
When FatSat is selected from the Saturation list, as shown in figure 6-69, the
fo llowing additional parameters are avai lable:
Figure 6-69. Clicking FatSat from the Saturation list displays additional parameters.
Wave- Provides options for the waveform of the fatsat pulse, as shown in
Figure 6-70. Each of these waveforms maintains a minimum TR, which limits
the number of slices available. H-Sinc Light suppresses lipids. H-Sinc Heavy
suppresses lipids and fatty protons, which precess at the same frequency as
water.
S1nc H-Sinc Ught H-Sinc
Figure 6-70. Wave options.
When acquiring T2-weighted images with a large FOY, the fo llowing settings
are recommended:
• Sine- When Sequence is DW EPI
• H-Sinc Light or H-Sinc Heavy- When Sequence is FSE or P r ime FSE
Duration -Allows the time (in milliseconds) for the fatsat pu lse to be entered.
Duration determines the fi·equency bandwidth fo r the patient signal that is
suppressed by the fatsat pulse. Time and frequency bandwidth are inversely
related (for example, a shorter time results in a wider bandwidth).
RF amp.[% ]- AIIows the strength (RF amplitude) of the fatsat pulse to be
entered. IfRF amp. [% ] is changed, the suppression effects offat signals will
change. l 00% of the initial value is the optimal strength calculated fi·om the
Wave and Dura tion parameters.
Off.F req[Hz]- Disp lays the frequency difference (in Hz) between the fat peak
and the water peak. Off.Fa·eq[Hz] is field-strength-dependent and should not be
changed. At l.2T, the value is - 173Hz. Off.Freq [Hz] is unavailable when F req.
graph is Auto or ON.
Copyright© 2012 by Hitachi Medical Systems America, Inc. All rights reserved.
Q54-53287v4
Scan Parameters 0 Segment- May be used to improve fat suppression results when Sequence is
BASG and Saturation is FatSat. Increasing the segment number divides the
fatsat pulse into segments. This may decrease scan time, but also decreases the
effectiveness of the fatsat pulse.
Additional Parameters when Segment FS is selected
When Saturation is Segment FS (for use with TIGRE sequences), Wave
options include Sine and H-Sinc, as shown in figure 6-71. The recommended
wave is H-Sinc, as it provides more consistent fat suppression.
Figure 6-71. Wave options.
Additional Parameters when Phase Cycle is selected
When Saturation is P base Cycle, the fo llowing additional parameter is
available, as shown in figure 6-72:
Quasi TimeRcs- May improve time resolution by sharing data. Quasi
T imeRes is available only when Multi scan mode (in the Scan Control area) is
F luoro or Dynamic.
off
off ON
Figure 6-72. Quasi TimeRes options.
Additional Parameters when Water Excitation is selected
When Saturation is Water Excitation, as shown in figure 6-73, the following
additional parameter is available:
Saturation
IM~M~!!~I == Water Exc1ta11o • •• 1- 1
1-1 1-2-1 1-3-3-1
Figure 6-73. Wave options.
Wave- Indicates the wave for the RF excitation pulse; each group of composite
pulses add up to 90 degrees. As the pulse number increases (and the total pulse
is longer), the water selection increases and the fat suppression effects improve;
however, the images will have more noise. The following options are available:
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0AS Is-MRI System Reference Manual YbehtJ ... tlilqHt
6-46
• 1-1 -0ne 45° pulse, one 45° pulse.
• 1-2-1 - 0ne 22.5° pulse, one 45° pulse (2x22.5°), one 22.5° pulse.
• 1-3-3- 1-0ne 11.25° pulse, one 33.75° pulse (3x 11.25°),
one 33.75° pulse (3 x 11.25°), one 11.25° pulse.
Additional Parameters when Water Saturation is selected
When Saturation is Wate•· Saturation, the following additional parameters are
available:
Wave- Displays the water saturation pulse excitation waveform.
Water Sat BW -Sets the water saturation pulse bandwidth (ppm).
Freq. Graph Parameter
All Saturation selections include the Freq. graph parameter, which is
explained below.
Freq. gra ph- Determines whether or not to display a frequency graph in
the Frequency Pt·escan window, which is described in the next section. The
following options are available, as shown in 6-74:
• off-Does not display the frequency graph.
• Auto- When the offset frequency for the fatsat pulse is determined in the
Exam window, that value is used during the acquisition. Auto can only be
used when Saturation is FatSat.
• ON-Displays the frequency graph . .. ,., off
off Auto ON
Figure 6-74. Freq. graph options.
Copyright© 2012 by Hitachi Medical Systems America, Inc. All rights reserved.
Note: Hitachi recommends using the Peak method because the Weighted method is prone to error (e.g., metal in field when the field homogeneity is distorted).
Q54-53287v4
Scan Parameters 0 Frequency Prescan Window
The Frequency P rescao window, as shown in figure 6-75, displays the
frequency graph results. This window appears at the beginning of a scan when
Freq. graph is ON or when Freq. gra ph is Auto and Satura tion is FatSat.
:y Prescan Water peak
Figure 6-75. The Frequency Prescan window.
This window contains the following features:
F req uency (MHz)-Displays the center frequency of water (MHz).
Offset F requency (MHz)- Represents the precessional frequency difference
(Hz) between fat and water. This value is field-strength-dependent and should
not be changed. At 1.2T, the value is -173Hz; this is the frequency of the fatsat
pulse.
Noise Threshold (%)-Used when Weighted is selected for the Search
Mode, which is described next in this section. Noise Threshold (%) allows the
threshold percentage to be selected for determin ing the center frequency by the
center of gravity method.
Search Mode-Allows the search method to be selected for determining
frequency values from the fo llowing options:
o Peak - Peak method, where the center frequency is set at the signal's
maximum frequency value.
o Weighted - Center of gravity method, where the center frequency is set to the
center of gravity for signal values at or greater than the threshold.
Reset Param - Returns the va lues on this window to their initial settings.
CONT lNUE button - Restarts the scan.
STOP button - Stops the scan.
6·47
0AS Is~ MRI System Reference Manual 1'1MI hUnt llqnet
6-48
The graph display, as shown in figure 6-76, has the fo llowing features:
Offset frequency (fat peak)
Signal value axis
Center frequency (water peak)
Frequency (MHz) axis
Figure 6-76. Frequency Prescan window features.
• Vertical axis-Signal value
• Horizontal axis - Frequency MHz)
• Green vertical line-Offset frequency (fat peak)
• Blue ve11icalline- Center frequency (water peak)
• Red horizonta l line- Threshold when using the center of gravity method (not
shown in figure 6-76)
• Orange poi.nt-Acquisition data point (not shown in figure 6-76)
A Caution If the center frequency is changed on the graph of the frequency prescan results,
there will be an offset produced in the position of the acquisition plane. The
reference image (scanogram) should be rescanned.
While the graph is displayed, if prescann ing is canceled using the Stop
button on the Frequency Prescan window or the Abort button on the control
panel, the frequencies that have been set will not be applied to all subsequent
acqu isitions.
In addition, once the center frequency and offset frequency have been set, they
will be maintained until one of the following types of acquisitions is performed:
• Acquisition with Freq. grapb set to ON.
• Acquisition with Prescan set to ON.
• Acquisition with the Exam window changed (for example, Sequence or other
parameters have been changed).
• Acquisition with the receiver coil changed.
Copyright© 2012 by Hitachi Medical Systems America, Inc. All rights reserved.
Note: Hitachi recommends clicking Sine from the Wave list for more uniform frequency response and better uniformity.
Q54-53287v4
Scan Parameters 0 T2W Prep (available with CardioSuite)
T2W P rep - A prepulse that enhances the T2 contrast of the imaging target.
When T2W Prep is applied to the 3D BASG sequence with FatSat, the tissue
contrast improves but the SNR drops slightly. The available options are:
• off- T2W Prep pulses are not in·adiated.
• ON- T2W Prep pulses are irradiated. When ON is selected, Duration is
displayed.
Dura tion - Sets the duration (in milliseconds) of the T2W P1·ep prepulse
application.
MTC The MTC (Magnetization Transfer Contrast) section of the ScanPa ra meterList
window (figure 6-77) contains the fol lowing parameters:
MTC 1
ON ·l S1nc
10 0
10 0
1 200
Figure 6· 77. The MTC section of the ScanParameterList window.
MTC- Changes the contrast of images by changing the magnetization
movement between bound water and free water. The MTC pulse is activated
prior to slice plane excitation.
Wave- Selects the waveform ofthe MTC pulse, as shown in figure 6-78.
QH Sine
S1nc Gauss1an
Figure 6-78. Wave options.
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0AS Is-MRI System Reference Manual YbehtJ ... tlilqHt
6-50
Wave options are Sine and Gaussian, which differ in function as shown in
figure 6-79.
Sine function type Gaussian function type
Duration Duration IIIII ~
~v
1 RF amp. 1 RF amp.
Figure 6-79. Function comparison for Wave options.
Duration-Indicates the activation time in milliseconds for the MTC pulse.
This value determines the frequency bandwidth of the MTC pulse. A shorter
duration produces a wider frequency bandwidth and a longer duration time
produces a narrower frequency bandwidth.
RF amp.IIJ.Tl -lndicates the activation strength (RF amplitude) of the MTC
pulse.
Off.F req[kz] -Indicates the offset frequency (in kHz) of the MTC pulse.
VENC
The VENC (Velocity Encoding) function uses phase information to acquire the
flow rate and flow direction of blood. The VENC section of the
ScanParameterList window (figure 6-80) contains the fo llowing parameters:
Figure 6-80. The VENC section of the ScanParameterList window.
Copyright© 2012 by Hitachi Medical Systems America, Inc. All rights reserved.
Q54-53287v4
Scan Parameters 0 VENC-Available when Sequence is PC (Phase Contrast). When VENC is
ON, a flow encode pulse is applied to target the blood flow.
The following parameters are available when VENC is ON:
Ta rget Vel. - lndicates the flow rate for the target vessel in centimeters per
second. This value is a vector volume with size and direction. The value of this
parameter is the maximum value that can be acquired on the flow rate image;
however, flow rates that exceed the value set wi ll be acquired as flows in the
reverse direction.
VENC Dir#- lndicates the number of axes where the flow encode pulse will
be applied. Provides the fo llowing options, as shown in figure 6-81 :
• 1 - Applies the flow encode pulse to one axis. Use the VENC Dir. parameter
(described next in this section) to select this axis.
• 3 -Applies the flow encode pulse to the following three axes: the A- P axis
(front-back direction), the R-L axis (right-left direction), and the H-F axis
(body axis direction).
Figure 6·81. VENC Dlr# options.
VENC Dir. - Available when VENC Dir# is 1. Allows you to select the one
axis to which the flow encode pulse will be applied. As shown in figure 6-82, the
options are.
• A-P- Applies the flow encode pulse to the A-P axis.
o R-L-Applies the flow encode pulse to the R-L axis.
o H-F - Applies the flow encode pulse to the H-F axis.
•••• IEJF 9
A-P R-L H-F
Figure 6-82. VENC Dir. options.
Vel. Image- Reconstructs a flow velocity image in each axis, in addition to the
differential combination image.
Comb. Image- Reconstructs the differential combination image (angiography
image); defaults to ON. These images can be used for the Ml P post-processing
task. This task is described in the "Task MIP" section of Chapter 8, " Post
Processing Tasks."
6. 51
0AS Is-MRI System Reference Manual YbehtJ ... tlilqHt
Note: When a multi-slab scan is performed using SSP, the following must be considered when selecting the Rate parameter:
Since the slab is excited when sloped in the slice direction with SSP, the flip angle varies at the higher and lower parts. The difference of this flip angle appears as contrast.
The difference of contrast of stationary tissue appears as the edge of a step between slabs. However, the step is not always the same, and will not be prominent if Rate is low, but will be if Rate is high.
Note: Single-slab scanning is recommended with SSP.
6-52
SSP The SSP section of the ScanParameterL ist window (figure 6-83) contains the
following parameters:
SSP .• •· (ON ·J .... 11 5 I· I· ! 1!§!1.11 F < H I H<F
F<H .....
Figure 6-83. The SSP section of the ScanParameterList window.
SSP (Sloped Slab Profile)- Applies an RF pulse using gradient profile
excitation to minimize the saturation of blood flow within a volume (slab).
SSP is available when Sequence is TOF and 2D/3D is 3D. Changing the RF
excitation angle inside the slab affects the spins (in the flowing blood) as they
move through the volume. A smaller angle is needed for blood entering the
volume; the angle shou ld increase as the blood flows tlll'ough the volume.
Rate - Indicates the RF pulse ratio (slope) of inflow region to outflow region.
A larger volume demands a steeper slope, as it takes more time for blood to flow
through this larger area. The options are:
• 1.5 - The ratio is 1:1.5 (smallest slope).
• 2 - The ratio is I :2.
• 2.5 - The ratio is I :2.5.
• 3 - The ratio is 1:3 (steepest slope).
Direction - Specifies the RF pulse gradient direction. Select one of the
following options to increase the RF pulse in the specified direction:
• F<H- Increases from feet to head.
• H <F- Increases from head to feet.
• R <L- In creases from right to left.
• L<R-Jncreases from left to right.
• A<P- Increases from anterior to posterior.
• P<A- lncreases from posterior to anterior.
The options that can be selected for each sl ice plane are as follows:
• For AX-F<H and H<F
• For SAG- R<L and L<R
• For COR- A<P and P<A
Example: For the Circle of Wi llis (COW), the F<H direction would be used.
Th is places the smaller angle at the feet, where the blood enters the volume.
Copyright@2012 by Hitachi Medical Systems America, Inc. All rights reserved.
Note: Since MPG pulses are applied in Diffusion Tensor Imaging, it is sensitive to motion. In multishot measurements. to reduce artifacts due to motion. use pads to immobilize the patient as much as possible and use gating.
Q54-53287v4
Scan Parameters 0 MPG
Motion Probing Grad ients (MPG) are the gradient magnetic fields used in
diffusion weighted imaging. These gradients are needed when imaging the
proton diffusion phenomenon. The MPG section is avai lable when Sequence is
DW EPI.
The MPG section of the ScanParameterList window contains the following
parameters:
MPG (Motion Probing Gradient) - Specifies if the MPG function is ON or off.
MPG Dir#-Selects the number of <L'\es to which the MPG pulse is applied.
The fo llowing options are available, as shown in figure 6-84:
• Single-Applies the MPG pu lse to the A-P, R-L, or H-F axis.
• Trace-Applies the MPG pulse to the three axes in sequence.
• Tensor6- Applies the MPG pulse to six axes, which inc ludes A-P, R-L, H-F,
and three oblique directions: A-P with R-L, A-P with H-F, and H-F with R-L
(this is a purchasable option associated with the Diffusion TensorSuite).
• Tensor7-Applies the MPG pulse to seven axes (this is a purchasable option
associated with the Tensor Suite).
• Tensorl3-Applies the MPG pulse to 13 axes (this is a purchasable option
associated with the Tensor Suite).
• Tensor21 - Applies the MPG pulse to 21 axes (this is a purchasable option
associated with the Tensor Suite).
I' &•• ll Single
S1rgle Trace Tens011l Tensor7 Tensor13 Tensor21
Figure 6-84. MPG Dir# options.
G rad ient Mode- Indicates the mode to which the MPG pulse is applied. The
following options are provided, as shown in figure 6-85:
• Single- Applies the MPG pulse to the axis selected in MPG Dir #.
• Complex-Applies the MPG pulse to the three axes (A-P, R-L, H-F).
This parameter is unavailable when MPG Dir# is Tensor6, Tensor7, Tensor13,
or Tensor21.
IAIEFIIIW Single . [I Single Complex
Figure 6-85. Gradient Mode options.
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0AS Is~ MRI System Reference Manual Th41hU ... tMqnet
Note: Hitachi recommends using a b-factor of 1000, which is the clinical standard. Different b-factors can be used based on radiologist preference.
6-54
b-factor-AIIows the b-factor ofthe MPG pulse to be entered. The application
time and application strength of the MPG pulse are automatically calculated
based on the b-factor value.
MPG Dit·. -AIIows you to select the application axis. MPG Dir. is avai lable
when MPG Dir# is Single. The following options are provided, as shown in
figure 6-86:
• A-P-Applies the MPG pulse to the A-P axis.
• R-L-Applies the MPG pulse to the R-L axis.
• H-F - Applies the MPG pulse to the H-F axis.
Figure 6-86. MPG Dir. options.
Scan Control
The Scan Control section of the ScanParameterList window (figure 6-87),
contains the following parameters:
·T ·T
Mi.@,!. ON @ii .. A.I· (Fo=ff=---..,. r
'''11'·1.& I off • l 5*"3- r off ·1 ij.IMMHI[ ott . ]
iiiJ¥!i Auto
Figure 6-87. The Scan Control section of the ScanParameterList window.
Copyright© 2012 by Hitachi Medical Systems America, Inc. All rights reserved.
Q54-53287v4
Scan Parameters 0 Scan mode -Specifies the mode, if scans are to be repeated. The following
options are provided, as shown in figure 6-88:
• Once- Repeats only once.
• Discontinuous- The system asks with each repetition whether to perform the
scan or not.
• Every - Perfonns a scan the number of times equal to the va lue specified in
the R epeat Number parameter, described later in this section.
IIIIIII~JE~w~~~----~ Once
Figure 6-88. Scan mode options.
Multi scan mode- Specifies the performance mode for the scan. The following
options are available, as shown in figure 6-89:
• Normal--Performs a normal scan.
• Dynamic -Perfonns a scan that repeats multiple times. The time interval for
scans to be repeated can be set.
• Fluoro--Repeats a scan a number oftimes in as short a period as possible.
During scanning, parameters can be changed in real time.
IIMF!,I,;;ea Normal ~----'-------1
Normal Oynam1c Fluoro
Figure 6-89. Multi scan mode options.
Wait mode--Specifies the scan wait mode. The fo llowing options are
available, as shown in figure 6-90:
• off- Does not pause before starting a scan.
• Auto - When Wait# is used to perform a multi-acquisition scan with multiple
breath holds, Auto enables the Auto Voice function to automatically give
breath-hold instructions for each acquisition. The user does not have to press
the CONTINUE button for each acqu isition to be acquired.
• ON- Pauses before starting the scan once the prescan is fi nished; timing of
the pause is detenn ined by the value in Wait#.
*iiMf ~o~ff----'-------1 off Auto ON
Figure 6-90. Multi scan mode options.
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0AS Is-MRI System Reference Manual YbehtJ ... tlilqHt
6-56
Wait#- Indicates the number of acquisitions the system will perform prior to
pausing. Wait# is avai lable when Multi scan mode is N01·mal or Dynamic,
Wait mode is ON, and Multi Acquisition (in the Seq. Parameter area) is 2 or
more. Wait# must be one number lower than the va lue in Multi Acquisition.
The following options are available:
• 0- Scanning is petformed continuously.
• ! - Pauses once before starting the main acqu isition; the system counts the
prescan as the first acquisition.
• 2 or more- Pauses after performing two or more acquisitions, depending on
the number of acqu isitions set in Multi Acquisition . For example, with Multi
Acquisition set to 5, and Wait# set to 3 , the system will perform the prescan
and two additional acqu isitions before pausing.
After pausing, click the CONTINUE button (figure 6-9 1) to resume scan ning.
Figure 6-91. Click CONTINUE to resume scanning.
BH T ime- Indicates the longest of scan times from standby status to next
standby status. BH Time is displayed when Wait# is not 0.
Sta r t wait time-Sets the wait time before the scan sta1ts. This is displayed as
minutes:seconds.tenths-of-seconds, as shown in figure 6-92. Start wait time is
only available when Multi scan mode is Normal and Wait mode is off.
@fh@lii!i loo·oo o
Figure 6-92. Start walt time.
Repeat Number - Specifies the number of repetitions of the scan. Repeat
Number is only available when M ulti scan mode is Normal and Wait mode is
off.
No of scan set-Antows you to specify the num ber of scan repetitions and the
repetition interval (or wait) for each set (scans can be divided into a number of
sets with a maximum of 3). No of scan set is available when Multi scan mode
is Dynamic.
Copyright@2012 by Hitachi Medical Systems America, Inc. All rights reserved.
Q54-53287v4
Scan Parameters 0 Pre-Cont. (Pre-Contrast) - Specifies the number of repetitions for the first set of scans. Figure 6-93 indicates three repetitions for this first set.
delay time (for Pre-Cont.) - Specifies the wait time for the start of the first set.
This is displayed as minutes:seconds.tenths-of-seconds.
gap time (for Pre-Cont.)-Specifies d1e interval (in seconds) between
repetitions of the first set. Pre-Cont. must be set to 2 or more.
Scan#1 1st Gap Time
Scan#2 1st Gap Time
Scan#3
.. • .. ... .. • Individual Scan Time Individual Scan Time Individual Scan Time
Figure 6-93. Pre contrast illustration.
wait mode (for Pre-Cont.) - Provides the following options for the first set of repetitions:
• off- Does not pause when sta1ting.
• Every -Pauses with each repetition. When Every is selected, gap time is
hidden from view.
• Once- Pauses only for the first repetition.
After pausing, c lick the CONTINUE button to resume scanning.
Ea rly Post Cont. (Early Post Contrast)- Specifies tbe number of repetitions
for the second set of scans. Early Post Cont. is available when No of scan set is
set to 2 or 3.
delay time (for Early Post Cont.)-Specifies the wait time for the start of the
second set. This is displayed as minutes:seconds.tenths-of-seconds.
gap time (for Early Post Cont.) - Specifies the interval (in seconds) between
repetitions of the second set. Early Post Coot. must be 2 or more.
wait mode (for Early Post Cont.)- Provides the following options for the
second set of repetitions:
• off- Does not pause when starting.
• Every- Pauses with each repetition. When Every is selected, gap time is hidden from view.
• Once- Pauses only for the first repetition.
After pausing, click the CONTINUE button to resume scanning.
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0AS Is-MRI System Reference Manual YbehtJ ... tlilqHt
6-58
Late Post Cont. (Late Post Contrast) - AIIows you to specify the number of
repetitions for the third set of scans. Late Post Cont. is available when No of scan set is set to the maximum va lue of3, as shown in figure 6-94.
Figure 6-94. Late Post Cont. is available when No of scan set is 3 (max. value).
delay time (for Late Post Cont.) -Specifies the wait t ime for the start of the
third set. This is displayed as minutes:seconds.tenths-of-seconds.
gap time (for Late Post Cont.)- Specifi es the interval (in seconds) between
repetitions of the third set. gap time is avai lable when Late Post Cont. is 2 or
more.
wait mode (for Late Post Cont.) - Provides the following options for the third
set of repetitions.
• off- Does not pause when starting.
• Every- Pauses w ith each repetition. When Every is selected, gap time is
hidden from view.
• Once- Pauses on ly for the first repetition.
After pausing, c lick the CONTINUE button to resume scann ing.
Copyright© 2012 by Hitachi Medical Systems America, Inc. All rights reserved.
Q54-53287v4
Scan Parameters 0 Contrast agent-Allows a contrast agent to be specified , when scanning with a
contrast agent (figu re 6-95). If Multi scan mode is Dyna mic, No of scan set
must be a value greater than I to make Contrast agent available. The list of
contrast agent options can be customized in the Patient Registration Setting
window. Refer to Chapter 4, "Patient In formation Functious," fo r complete
contrast agent option list customization details.
HM(ott ·I off None Femseltz Feme arrvnon1um crtrate Fendex Ferumax>des ProHance Gadotendol Magn..,st MegiUilWle gadapentetate Gad PrimCMst
Figure 6-95. Contrast agent options.
Volumelml] - Volume[ml] is available when a Contrast agent is selected. Sets
the volume of contrast agent to be used in milliliters, as shown in figure 6-96.
Figure 6-96. Volume[ml] example.
Travel T ime- Used during contrast-enhanced magnetic resonance angiography
(CE-MRA). Enter the time it will take for contrast to arrive at the target area,
wh ich is determined from the test injection during the dynam ic scan
measurement (figure 6-97).
MM+g;;w Gad
... [30:0"" =r 9 I £ 0
"i'"IA I oo 24 o I
Figure 6-97. Travel Time example.
Additional parameters displayed under Travel Time include:
OffsetT ime-Used during CE-MRA. Displays the time that should be the
initial setting for the stop watch. The contrast agent is to be injected when the
stop watch reaches zero.
ContinueTime-Uscd during CE-MRA. Displays the timing when the contrast
agent is injected and the CONTINUE button is c licked.
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0AS Is· MRI System Reference Manual n. htJ•t llqJMt
6-60
O rg. I mage- Specifi es whether or not to reconstruct the source images, as
shown in figure 6-98. Org. Image is avai lable when M ulti scan mode is
Dynamic or F luoro, and Sub. Image (described next in this section) is Fixed,
Moved, or FxMv.
i¥1Qipiil ON
J, off ON
Miiii' ON
@ii;,pi!l Fixed
Figure 6-98. Org. Image and Sub. Image settings to reconstruct source images.
Sub. Image-Specifies the method for creating subtraction images for dynamic
scans. Sub. Image is available when Multi scan mode is Dynamic or Fluoro.
The fo llowing options are available, as shown in figure 6-99:
• off- Does not create a subtraction image.
• Fixed-Creates subtraction images using the first scan as the mask for all
subsequent scans (fixed mask).
• Moved- Creates subtraction images in wh ich each scan uses the previous
scan as its mask (moved mask).
• FxMv-Creates both types of subtraction images: fixed and moved.
A Caution
off Fixed Moved rxMv
Figure 6-99. Sub. Image options.
When subtraction is pe1formed, immobilize the patient as much as possible so
the images are as unsusceptible as possible to body movements.
The examples show how fixed and moved subtraction images are created:
Example: In fixed subtraction, scan I is subtracted from scan 2, scan 1 is
subtracted from scan 3, and so on. The mask is fixed using scan 1 (figure 6-1 00).
Fixed-subtracts 2-1 3-1 4-1
Figure 6-100. A fixed subtraction example.
Copyright@ 2012 by Hitachi Medical Systems America, Inc. All rights reserved.
Q54-53287v4
Scan Parameters 0 Example: In moved subtraction, scan 1 is subtracted from scan 2, scan 2 is
subtracted from scan 3, and so on. The mask moves from scan to scan (fi gure
6-10 1).
Moved-subtracts 2-1 3-2 4-3
Figure 6-101. A moved subtraction example.
Sub. Mask Start#- A IIows you to enter the number of the scan that statts the
subtraction processing when M ulti scan mode ( in the Scan Con trol area) is
Fluoro or Dyna mic. A black image (an image with a ll pixel values set to 0) is
output until the start of subtraction processing. The examp·les show how images
are created when the va lue for th is parameter is set to 3.
Example: Fixed mask subtraction, where scan 3 is the mask scan (figure 6-1 02).
Figure 6-102. Fixed mask subtraction using a Sub. Mask Start# value of 3.
Example: Moved mask subtraction where scan 3 is the first mask scan (figure
6-103).
Figure 6-103. Moved mask subtraction using a Sub. Mask Start# value of 3.
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0AS Is~ MRI System Reference Manual T'MhtJent MqHt
Note: If moving the patient table during volume shimming correction, the shimming correction effect is lost. Therefore, movement of the patient table by the Centering option is disabled when the center of scan position is included within the volume shimming scan region. If the center of scan position is not included within the volume shimming scan region, the result of volume shimming is canceled and the patient table is moved.
Note: Static magnetic field distribution data of the volume shimming to be used in regional shimming needs to be acquired again when moving the patient table with the Centering option.
Note: When Shading is NATURAL or when RAPID Mode is RCM, a warning message is displayed prompting you to redo the S-Map measurement if the patient table is moved approximaely 2 inches (Scm) or more by the Centering option. When aliasing artifact or nonuniformity of sensitivity occurs in a scanned image, redo the S-Map measurement.
6-62
When Multi scan mode is Dynamic, Sub. Mask Start# cannot be greater than
the sum of the Pt·e-Cont., Early Post Cont., and Late Post Cont. values.
Disk save-Available when Multi scan mode is Fluoro. Provides the
following options for saving images to the database (figure 6-1 04 ).
• off- Only the images for which the SAVE butto11 on the Exam window was
clicked wi ll be saved to the database.
• ON- Saves all images to the database.
Figure 6-104. Disk save options.
Table move-Provides the following options for moving the patient table, as
shown in figure 6-l 05:
• off- Does not move the table.
• Centering- Moves the table to the center of the magnetic field , depending on
the position of the acquisition plane.
• Manual-Moves the table to the position that has been entered in the
Position[mm] parameter (described next in this section).
off
off Centering Manual
Figure 6-105. Disk save options.
Posit ion[mm]- Available when Table move is Manual. Allows you to enter
the distance of patient table movement in mill imeters, as shown in figure 6-106.
==·= r Manual •J :;;..§ =:J· l· l
Figure 6-106. The Position[mm] parameter.
Copyright@2012 by Hitachi Medical Systems America, Inc. All rights reserved.
Note: When Auto Voice is ON, the following parameter checks and recalculations are made:
If gap time between each scan (Pre-Cont .. Early Post Cont., and Late Post Cont. l in Dynamic scan mode is shorter than the voice output time (SCANEND(Every) t SCANSTART(Every)). then gap time ts recalculated. If wait mode is set to Every, delay time is recalculated.
When wait mode is off for each scan in Dynam1c scan mode and delay time is shorter than the voice output time (SCANEND(Every) t SCANSTART(Every)). delay time is recalculated.
When wait mode is off for each scan in Dynamic scan mode and delay time is shorter than the SCANSTART(Once) or SCANSTART(Every) time, de/a}' time is recalculated.
Note: When Multi scan mode is Fluoro (or Normal and Wait mode is off and a Repeat Number value is specified). phrases are not output during each scan repetition even if SCANEND(Every) and SCANSTART(Every) are set to ON.
054·53287v4
Scan Parameters 0 Table Wait Mode- Enables/disables the patient table wait mode:
• off- Wait mode is not activated.
• ON- Wait mode is activated. Press the CONTINUE button to move the table.
C hime (available only when Auto Voice option is not r·egiste red) - Enables/
disables the chime sound when the patient table is moved:
• o ff- The chime does not sound when the patient table is moved.
• ON- The chime sounds before the table is moved ..
Auto Voice- Specifies whether or not to output an auto voice pattern. The
auto voice pattern can be created in the A uto Voice Setting window, as shown
in figure 6-107. For more information about creating an auto voice pattern, see
the "Auto Voice Setting Window" section of Chapter 9, "Additional Launcher
Functions."
When Auto Voice is off, Start wait time (when Multi scan mode is Normal
or Fluoro) or any of the delay time text boxes (when Multi scan mode is
Dy namic) automatically reset (display 00:00.0 instead ofthe minutes, seconds,
and tenths of seconds that were entered).
After creating a new auto voice pattern, you will need to close and reopen the
Exam window. Auto Voice then becomes available.
Figure 6-107. The Auto Voice Setting window.
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0AS Is~ MRI System Reference Manual T'MhtJent MqHt
Note: • When performing RAPID
sequences, use RAPID receiver coils.
• Some RAPID coils have a restriction on the phase encode direction available for scanning.
• The RAPID factor and direction is different for each RAPID coil.
• Image quality could be reduced if the imaging center deviates greatly from the receiver coil center.
• Image quality could be reduced if slab thickness is set to a smaller value during a RAPID sequence in the slice direction.
Note: With EPI sequence and primeFSE!primeFIR sequence (only EchoAI/ocation is ADA), RAPID measurement makes that E. Factor decreases with Shot Num. fixed and the total scan time does not decrease.
6-64
Sync. StopWatch -Starts the timing in the StopWatch window simulta neous ly
with the acquisition. Choose from the following options, as shown in figure
6~108:
• off- Does not synchronize the start of the StopWatch window with the
acquis ition.
• ON- Synchronizes the start ofthe StopWatch w indow with the acquisition.
f .IMMMNM off off ON
Figure 6-108. Sync. StopWatch options.
P rescan- Specifies the prescan mode. Choose from the following options, as
shown in figu re 6-109:
• Auto-Automatically performs appropriate prescan measurements based on
data from the previous scan.
• ON - Performs prescan measurements at the beginning of the first scan,
acquiring new data. Th is setting should be used on the first scan for each new
patient.
RAPID
144*§ Auto Auto ON
Figure 6-109. Prescan options.
The Rapid Acquisition through a Parallel imaging Design (RAPID) function
shortens the scan time. By using multichannel receiver coils, phase encoding is
decreased during the acqu isition according to the value set in the RAPID box.
Generally, when decreasing the phase encod ing for an acquisition, aliasing
is produced in the image following reconstruction. The RAPID acquisition
function acquires the data using multichannel receiver coil s. It develops the
image using a sensitivity map of the receive r coils, thus e liminating aliasing
and shortening the scan time. The SNR of the image is reduced as the value of
RAPID is increased.
You cannot use RAPID unless you perform an S-map that covers the imaging
region. When performing an S-map with RCM, set the imaging region so that it
sufficiently covers the area of interest. If this area is not sufficiently covered, an
error wi ll occur when starting the main scan.
Duri.ng S-rmp with RCM, a wide imaging region is captured using the TR Body
coil. S ince the scanogram is performed using the RF coi l, care is required so that
even regions that are not captured in the scanogram do not cause wrap artifacts.
Copyright© 2012 by Hitachi Medical Systems America, Inc. All rights reserved.
Note: Using ADA and RAPID results in a decrease in Echo factor per shot. so that the slice number can be increased without increasing scan time. When RAPID is utilized and Echo A/Joe. is set to ADA for EPI, Prime FSE. or Prime FIR sequences. image blurring and distortion are minimized. resulting in improved image quality.
Q54-53287v4
Scan Parameters 0 For example: When taking images of the trunk of a patient's body, the patient's
anns outside the FOV might cause wrap artifacts during S-map acquisition.
Th is could lead to faulty sensitivity correction in the main scan, and therefore
care is required when specify ing the settings. Similarly, when taking images
of lower extremities such as the knees or upper extremities such as the e lbows,
other body areas outside the FOV might cause wrap artifacts during S-map
acquis ition. This could lead to faulty sensitivity correction in the main scan, and
therefore care is required when specifying the settings.
Since the system is sensitive to any movement by the patient, it is important
to have the patient remain as still as possible during S-map Normal mode
acqu is ition. To accommodate for patient motion such as breathing and
peristalsis, we recommend the Nest mode ofthe S-Map sequence.
ln addition, the following precautions are required to acquire effective three
dimens ional sensitivity distribution data when using S-Map:
• Specific positioning and imaging parameter settings to prevent wrap a11ifacts
in the region where the main scan is to be perfonned.
• A I though the cross-section to be acquired depends on the a rea where imaging
is being performed, to avoid wrap artifacts we recommend that you select
COR or SAG, in which the frequency direction is usually along the axis of the
patient's body.
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0AS Is~ MRI System Reference Manual Th41hU ... tMqnet
Note: Figure 6-110 shows how the RAPID function creates images.
Because aliasing artifact appears stronger in the center area of the
image when performing RAPID 0 scans, it is necessary to set a slightly larger FOV and to set the imaging area in the phase direction to cover the entire Coil sensitivity map
imaging object using the Anti.aliasing function.
6-66
Aliased image
Image development anti-aliasing
Figure 6-110. /mage creation using RAPID.
0 Resulting image
The RAPID section of the ScanParameterList window contains the following
parameters:
RAPID(Phase), RAPID(Siice) - Decreases the phase and slice encod ing
in the acquisition according to the values entered, resulting in reduced scan
duration. RAPID(Phase) and RAPID(Siice) values range from 1.0 to 4.0,
with a precision of 0.1 step. As va lues are entered in the RAPID(Phase) and
RAPID(Siice) boxes, RAPID(Total) is automatically calculated and updated.
For example, when RAPID(Phase) is 1.4 and RAPID(Siice) is I .6,
RAPID(Total) will be 2.2 (the second digit to the right of the decimal point
is omitted). RAPID acquisition is not performed when RAPID(Phase) and
RAPID(Siice) are both 1.0, wh ich is the defau lt va lue.
RAPID(Siice) is available when 2D/3D is 3D and Sequence is RSSG or
BASG. RAPID(Siice) is a lso available when 2D/3D is 3D, EchoTime Mode is
Optimized, and Sequence is FSE, FIR, primeFSE, or pl"imeFSR.
RAPID(Total)- Disp lays the product of the values entered in the
RAPID(Phase) and RAPID(Siice) boxes. This calculation is based on the
equation: RAPID(Phase) x RAPID(Siice) = RAPID(Total).
Copyright© 2012 by Hitachi Medical Systems America, Inc. All rights reserved.
Note: Because the timing to acquire a coil sensitivity map is different depending on the RAPID Mode (even if the same RAPID factor is set). the reduction rates of the scan times are different.
Note: Because data for a sensitivity map is acquired during the prescan in PCM mode. the prescan time is longer than that of other modes.
Note: Because data for a sensitivity map is acquired during the main scan in SCM mode, the scan time of the main scan is longer than that of other modes. However. the prescan time is the same as that of a normal scan.
Note: RCM mode uses an S-Map to prepare the 30 sensitivity map in advance. Acquisition of a 30 sensitivity map using an S-Map urder typical imaging conditions takes approximately 40 seconds.
Q54-53287v4
Scan Parameters 0 Mode- Specifies the calibration method for the RAPID acquis ition. The
method may be selected automatically, based on the Sequence that has been
selected. The following options are ava ilable, as shown in figure 6-111:
• PCM (Prescan Calibration Method)-Acquires the coil sensitivity map during
prescan. T he additional options available with this mode are described next in
this section.
• SCM (Self Calibration Method)-Acquires the coil sensitivity map during the
RA PID scan. This is the default mode when certain sequences are selected.
• RCM (Reference Calibration Mode)- Uses the sensitivity map acquired
duri ng the S-map scan.
RCM I SCM PCM
Figure 6-111. RAPID Mode options.
When Mode is PCM, the fol lowing additional parameters are available:
PCM Mod e-Determines the control method for collecting a coil sensitivity
map during prescan. The default value is Auto, as shown in figure 6-112.
Auto
Figure 6-112. The PCM Mode parameter.
The following options are available, as shown in figure 6-113:
• Auto- Automatically determines whether or not to use the coil sensitivity
map collected during the previous prescan. If it can be used, reacquisition
ofthe coil sensitivity map is not performed. If there is no previous coil
sensitivity map, it is collected. Reacquisition of the sensitivity map wi II not
be performed if the fo llowing conditions are the same as during the previous
collection:
- Slice position, oblique angle, slice interval
-Slice plane, phase direction
- Multi-sl ice, multi-acquisition
- FOV, reconstruction matrix
• ON- Collects a sensitivity map during each prescan.
Au10 ON
Figure 6-113. PCM Mode options.
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0AS Is-MRI System Reference Manual YbehtJ ... tlilqHt
6-68
PCM Wait mode- Specifi es whether or not to have a wait mode before
collecting a coi l sensitivity map during the prescan. Choose from the following
options, as shown in figure 6-114:
• off-Does not go to standby before collecting a coil sensitivity map.
• ON - The status changes to standby before co llecting a coil sensitivity map.
Figure 6-114. PCM Wait mode options.
PCM NSA-Sets the number of signal averages when collecting the co il
sensitiv ity map duri11g the prescan. The larger the value, the better the image
quality becomes; however, the prescan time is increased. The default (init ial
value) is I , with a maximum value of 8.
Gating
The Gating section of the ScanParameterList window contai ns the following
parameters:
Gating-Allows the type of gated scan to be selected. Choose from the
fo llowing options, as shown in figure 6-1 15:
• off-Gated scan not selected.
• MS-ECG- Eiectrocardiograph (pu lse wave) gated scan selected.
• Cine-Cine gated scan selected.
• Resp- Respiratory gated scan selected .
• ij (off · P off MS.ECG Cine Resp
Figure 6-115. Gating options.
The additional parameters that are available will vary with the type of gating
selected, the Sequence that is selected, and related scan parameters. In the
fo llowing parameter descriptions, applicable gating types are included in
parentheses after the parameter names, as shown in the example:
Example: Beat Rate (MS-ECG, C ine, Resp) indicates that the Beat Rate parameter applies to MS-ECG, Cine, and Resp gati ng.
Beat Rate (MS-EC, C ine, Resp)-Enter the heart rate (in beats per minute) for
MS-ECG and Cine gating. Enter the respirato1y rate for Resp gating. The heart/
respirat01y rate is displayed in the WaveForm window.
Copyright© 2012 by Hitachi Medical Systems America, Inc. All rights reserved.
Q54-53287v4
Scan Parameters 0 # HB Prep (Cine [available with CardioSuite])-lndicates the reserve heart rate
prior to petforming the acquisition. The Gate Mode parameter (located two
parameters below# HB Prep) must be Delayed, as shown in figure 6- 11 6.
Mil& C1ne . ·1 .•. , 66 I· '· ' ""1141 2 I· ... #1111·A111' ECG :1 Mil' ll Delayed _______:]
Figure 6-116. The # HB Prep parameter with the Delayed Gate Mode requirement
Gating Source (MS-ECG, Cine, Resp)- lndicates the signal source for the
gated scan. Select from the following options:
• ECG - Indicates the electrocardiograph as the signa I source. ECG can be
selected when Gating is MS-ECG or Cine, as shown in figure 6-117.
• Pulse- Indicates the peripheral pulse as the signal source. Pulse can be
selected when Gating is MS-ECG or Cine, as shown in figure 6- 117.
ECG Pulse
Gating is MS-ECG
ECG Pulse
Gating is Cine
Figure 6-117. Gating Source options.
• Resp- lndicates respiration as the signal source. Resp is the fixed default
when Gating parameter is Resp.
Gate Mode (MS-ECG, Cine) - Ind icates the electrocardiographic synchronous
mode. Choose from the fo llowing options, as shown in figure 6-118:
• Gate- Gate method
• Trigger- Trigger method
• Delayed-Delayed enhanced method (available with CardioSuite)
• MyoPer- Myocardial perfusion method (available with CardioSuite)
*I"' Gate
Gate Tngger Delayed
Per
Figure 6-118. Gate Mode options.
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0AS Is-MRI System Reference Manual YbehtJ ... tlilqHt
6-70
Resp Mode (Resp)- Indicates the respiratory synchronous mode; the fixed
default is Trigget·, as shown in figure 6-119 .
•• ,, Trigger
Figure 6-119. The Resp Mode parameter.
Count (MS-ECG, Cine, Resp) - lndicates the number ofR-wave intervals or
respiratory cycles needed to collect the desired amount of slices. The Count
value is dependent on the heaJt rate (a higher heart rate, with shorter R-R
intervals, requires an increased Count to obtain more slices). When Gate Mode
or Resp Mode is Trigger, Count affects the TR. The value of 1 is automatically
set when Gate Mode is Gate.
Multi Phase (Ci ne) - lndicates the number of images to be taken at the same
position but at different heart phases. In figure 6-120, Gating is Cine and Multi
Phase is 24.
Cine
''"' ll
Figure 6-119. The Mult Phase parameter.
Segment (MS-ECG [with CardioSuite], Cine) - lndicates the segment number.
Increasing the segment number allows less slices per R-R waveform. Segment
can be specified in the following cases, as shown in figure 6- 120:
• When Gate Mode is Gate
• When Gate Mode is Trigger and Sequence is BASG, SARGE, or RSSG
• When Gate Mode is Delayed and Sequence is BASG
Gate Mode is Gate, Segment is 3 Gate Mode is Trigger, Segment is 3
Figure 6-120. The Segment parameter.
Copyright@2012 by Hitachi Medical Systems America, Inc. All rights reserved.
Q54-53287v4
Scan Parameters 0 DelayMode (Resp) - lndicates the input unit for Delay measurement. Select
from the following:
• Time - Sets the Delay in milliseconds (ms). The Delay represents the time
from the trigger signal to the initial slice TE.
• Rate- Sets the Delay as a percentage(%). The Delay represents a percentage
of the breathing cycle from the trigger signal to the TE of the initial slice.
Delay[ms] (MS-ECG, C ine, Resp) - Indicates the time in milliseconds from the
trigger signal until the TE of the initially acquired slice.
Delay (%) ( Resp)-Indicates a percentage of the breathing cycle as the delay
from the trigger s ignal to the TE of the initial slice.
Interval (MS-ECG, Cine, Resp)- Indicates the time interval between the
collection of each s lice or each phase.
Echo Alloc. (MS-ECG, Cine)- AIIows selection of the echo allocation method.
This setting can be specified in the fo llowing cases:
• When Gate Mode is Gate
• When Gate Mode is Trigger and Sequence is BASG
Choose from the fo llowing options:
• Sequential - Arranges segments sequentially.
• Centric - Arranges segments centrica lly. Centric is available when Sequence
is BASG (2D), BASG (3D, with Gate Mode set to Trigger), SARGE (2D),
RSSG, PC, TOF, or RSSG EPI.
Figure 6-121 illustrates the allocation of acquisition data for the two Echo Alloc.
methods.
Phase encoding direction
Segment#1 Segment#4
Segment#2 Segment#3
Segment#3 Segment#2
Segment#4 Segment#1 Segment#5 Segment#1
Segment#6 Segment#2
Segment#? Segment#3
Segment#4
Sequential Centric
Figure 6-121. Allocation of acquisition data comparison for the Echo Alloc. methods.
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0AS Is~ MRI System Reference Manual 1'1MI hUnt llqnet
Note: When a gating procedure is started with Beat Rejection set to ON, use the value displayed in the WaveForm window (the patient's heart rate) to enter in the Beat Rate box (in the Gating section of the ScanParameterList window), and don't excessively narrow the range of the regular beat.
Note: When a gating procedure is started with Beat Rejection set to ON and 16 consecutive irregular heart beats are recorded, Beat Rejection is automatically switched to off.
6-72
Echo Shift-Allows the number of echo shifts to be entered. The range is
dependent on the number of segments. Figure 6- 122 shows the implementation
of echo shifts .
Phase encoding direction
Segment#1 Segment#2 Segment#3
Segment#6
Segment#1
Segment#2 j Segment#3
Segment#2
Segment#1
Segment#3
Segment#3
Segment#2 Segment#4 Segment#3 Segment#1 Segment#1 Segment#5 Segment#4 Segment#2 Segment#1 Segment#6 Segment#5 Segment#3 Segment#2
Sequential/shift: 0 Sequential/shift: 1 Centric/shiift: 0 Centric/shift: 1
Figure 6-122. An Echo Shift illustration.
Beat Rejection-An irregular hea11 rhythm or pulse (arrhythmia) can cause
image quality deterioration when Gating is MS-ECG or Cine. Beat Rejection
eliminates data acquired when arrhythmia occurs. Choose from the fo llowing
options:
• off-Data acquired when arrhythmia occurs is not eliminated.
• ON- Data acquired when arrhythmia occurs is eliminated. When Beat
Rejection is ON, Skip Beat, L level[%], and H level[%] are accessible.
A Caution The beat rejection function is not effective for patients that suffer from
arrhythmia due to cardiac disease.
Skip Beat -Specifies the number of normal beats sk ipped after an arrhythmia.
L level[% j- Enter the shortest regular hea11beat cycle (as a percentage of the
regular heartbeat cycle). The regular heartbeat cycle corresponds to the R-R
interval, which the system calculates based on Beat Rate.
H levei[%]- Enter the longest regular heartbeat cycle (as a percentage ofthe
regular heartbeat cycle). The regular heartbeat cycle corresponds to the R-R
interval, which the system calculates based on Beat Rate.
Summary of Gating Parameters
The following table provides a summary of scan conditions and the various
parameters that are available when Gating is MS-ECG, Cine or Resp, and
instructions for how the parameters should be set.
Copyright@2012 by Hitachi Medical Systems America, Inc. All rights reserved.
Scan Parameters 0 Parameters When the Gating parameter is:
Available MS-ECG C ine R esp
Beat Rate Enter the heart rate Enter the heart rate Enter the respiratory rate
Indicates reserve hea1t rate; # HB Prep Unavailable range is 0 to 2. Gate Mode Unavailable
must be set to Delayed1•
Gating Specify ECG or Pulse Specify ECG or Pulse Resp
Source
Gate Mode Specify Trigger, Gate, Specify Trigger, Gate,
Unavailable Delayed 1, or MyoPer1
• Delayed 1, or MyoPet·1•
Resp Mode Unava ilable Unavailable Trigger
Indicates the number of R Indicates the number of R Indicates the number of
Count waves; I is set if Gate Mode waves; I is set if Gate Mode respiratory cycles
is Gate. is Gate.
Indicates the number of Multi Phase Unavailable images at same position, but Unavailable
differing heart phases.
Enter a number if Gate Mode Enter a number if Gate Mode is: is: •Gate •Gate
OR OR
Segment •Trigger, with Sequence •Trigger, with Sequence
Unavailable set to BASG, SARGE, or set to BASG, SARGE, or RSSG RSSG
OR OR • Delayed 1, with Sequence set • Delayed 1, with Sequence set to BASG to BASG
Delay Mode Unavailable Unavailable Select Time (ms) or Rate(%)
Delay[ms] Indicates time from trigger Indicates time from trigger l t~dicates time from trigger signal to initial slice TE signal to initial slice TE s ignal to initial s lice TE
Enter rate(%) of breathing Delay(%) Unava ilable Unavailable cycle from trigger signal to
TE of initia l slice
Tntet-val Indicates scan time interval Indicates scan time interval lt1dicates scan time interval for each slice or phase for each slice or phase for each s lice or phase
Echo Alloc.- Choose from: Choose from: Gate Mode •Sequential • Sequential must be Gate OR OR
Unavailable (or Trigger •Centric (with SARGE, •Centric (with SARGE, with BASG RSSG, BASG, TOF, PC, or RSSG, BASG , TOF, PC, or sequence) RSSG EPI) RSSG EPI)
Beat Unavailable
Select off or ON. If ON, enter Unavailable
Rejection a Skip Beat value.
1 Available with CardioSuite.
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0AS/S~ MRI System RefeTence Manual n.. Pau ... .._
Parameters Available
Skip .Beat
L level[%]
H level[%]
Note:
When the Gating parameter is:
MS-ECG Cine Resp
Specifies the number of Unavailable normal beats skipped after an Unavailable
arrhythmia.
Sets a measurable range for Sets a measurable range for Sets a measurable range for trigger intervals when the beat trigger intervals when the beat trigger intervals when the beat parameter is off. When .Beat parameter is off. When Beat parameter is off. When .Beat Rejection is ON, sets the R-R Rejection is ON, sets the R-R Rejection is ON, sets the R-R interval ratio for the shortest interval ratio for the shor1est interval ratio for the shortest regular heartbeat cycle. regular heartbeat cycle. regular heartbeat cycle.
Sets the R-R interval ratio for
Unavailable the longest regular heartbeat.
Unavai lable Use when .Beat Rejection is ON.
NAVI
The NaviPulse (navigator acqu isition function) is an optional function used to
reduce scann ing artifacts in regions (such as the heart) where the position is
moved by breathing.
Navigator echo position and main scan region must be kept apart.
With this function , breathing movement is monitored by acquiring an additional
echo, called a navigator echo, from the region perpendicular to the diaphragm.
Using the monitored change in the position of the diaphragm, scann ing
is performed with the patient " free-breathing." The slice position can be
adjusted according to the displacement observed from the monitored breathing
movement.
6. 74
Figure 6-123 shows how the NaviPulse function works.
Head
[ Feet
Heart ... ·· This scan plane
~~~~·· ····· · · · ·· · · ·· ······· ····· · ···· r ~$~~~· ........ .... Diaphragm F I Breath gating for this scan I
i ··.. Acquisition position
for navigator echo --- I Monitoring breath movement I
Figure 6-123. NaviPulse illustration.
Copyright@ 2012 by Hitachi Medical Systems America, Inc. All rights reserved.
Q54-53287v4
Scan Parameters 0 The Navi section of the ScanParameterList window (figure 6- 124), contains
the fo llowing parameters:
Figure 6-124. The Navi section of the ScanParameterList window.
NaviPulse- Provides the fo llowing options, as shown in figure 6-125:
• off- Does not perform navigator acquisition.
• NaviGate- Performs navigator acquis ition.
• SlicePos- Available only when Sequence is BASG, performs navigator
acquisition and adjusts the slice position to compensate for s lice variation due
to respiratory movement.
off
off NavtGate Sl1cePos
Figure 6-125. NaviPulse options.
GateWiodow- lndicates the gate window width in millimeters. The
acquisition data is effective only when the position of the diaphragm is in the
gate window prescribed by this width. The default (initial value) is 3 mm.
Data Number - Indicates the number of acquis ition points for the navigator
data. The selection can be 64, 128, or 256 points, as shown in figure 6-1 26 .
•••• ,.,_64;,;_ ___ --r 64 128 256
Figure 6-126. Data Number options.
CorrCoeff-Available when NaviPulse is SlicePos. CorrCoeff sets the ratio
of variation in sl ice position (due to respiratory movement) to the value of the
position adjustment. For example, if the respiratory movement detected by the
navigator monitor is I Omm and the CorrCoeff is set to 0.6, the slice is adjusted
by6mm.
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6-76
NaviMonitor - Indicates the method for the NaviMonitor acquisition during
the prescan. Choose from the following options, as shown in figure 6-127:
• ON-NaviMonitor acquisition is always performed prior to an acquisition.
• Auto-In cases where the monitor acquisition has been performed for the same
acquisition, the system decides if the data is usable or not. If it is usable, the
acquisition will start without the petformance of a monitor acquisition during
the prescan. If it is not usable, a NaviMonitor acquisition will be perfonned.
Figure 6-127. NaviMonitor options.
Monitor Time-Indicates the time for the NaviMonitor acquisition.
PAPE Partial Phase Encode (PAPE) is an optional function used to improve temporal
resolution while maintaining the spatial resolution of the image.
The PAPE section of the ScanParameterList window (figure 6- 128) contains
the following parameters:
PAPE ljj ON
e;;.iil.;; lr-oo-·-17_3_~..,,
Wj,jj§ [s ! ... "': ' 11!fiDIM[4o I I- '
L-....,--~
*!·*'! 8
F;gure 6-128. The PAPE section of the ScanParameterList window.
PAPE - Provides the following options:
• off- PAPE is off.
• ON- PAPE is on.
PAPE can be set to ON when Multi scan mode is Dynamic or Fluoro, and one
of the following combinations are selected from the 2D/3D and Sequence lists:
• 2D and SARGE
• 2D and BASG
• 2D and TRSG
• 2D and RSSG
• 3D and RSSG
Scan Time-Displays time, but is unavailable. This is the time needed to perform the acquisition, while ignoring the K-space high frequency waves.
Copyright@ 2012 by Hitachi Medical Systems America, Inc. All rights reserved.
Note: It is recommended to set Data Rate[%] higher when scanning a region with movement.
Q54-53287v4
Scan Parameters 0 Segment- Indicates the number of segments to be partitioned for K-space. As
the number of segments increases, the scan time per image becomes shorter,
but the update interval for high frequency data becomes longer. The selections
include 3, 5, 7, or 9.
Data Ra teJ% 1- lndicates the ratio for low-frequency data that will definitely
be measured(%). As this rate is increased, image quality improves but temporal
resolution degrades. The range is from I 0 to 60 percent, in five percent
increments.
Scan Cycle- Displays the number of cycles. Scan Cycle is set automatically
and remains at one number lower than the setting for Segment. Scan Cycle
options include: 2, 4, 6, orR.
Filter/PostProcessing
The F ilter/PostProcessing section of the ScanParameterList window conta ins
the fo llowing parameters:
Ot·g.Jmage- Specifies whether or not to reconstruct original images. Org.
Image is available when Sequence is PC (Phase Contrast). Choose from the
following options, as shown in figure 6- 129:
• off- Does not reconstruct original images.
• ON- Reconstructs original images.
l6aPI!Miii •• l~~-~-------f·l1
Figure 6·129. Org.lmage options.
Calc.Image- Specifies whether or not to create differential images for scanned
images. Depending on sequence selected and imaging conditions, the Calc.
Image options might not be available, might be set automatically, or may not
even be displayed. Available options are:
• off- Does not create differential images.
• Sub-Creates differential images.
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6-78
Image Type-Specifies the type of images to be displayed. Image Type may
be available, or may be set automatically (unavailable), depending on the option
selected from the Sequence list.
The following options are available when Sequence is IR or FIR (figure 6- 130):
• Abs- Displays absolute value images.
• Real- Displays Real images.
••+ 1'-A_b.:....s ----t Abs Real
Figure 6-130. Image Type options.
The following option is automatically set when Sequence is Shim (figure 6-13 I):
• Phase- Displays Phase images.
QM·i· Phase
Figure 6-131. Image Type option when Sequence is Shim.
RawData Save-Available to Hitachi fie ld serv ice engineers. Specifies whether
or not to save the raw data to the database before image reconstruction. As
shown in figure 6-132, the options are:
• off- Does not save raw data to the database.
• ON -Saves raw data to the database.
ptD@Moff off ON
Figure 6-132. RawData Save options.
Truncation - Filtering that can be used to reduce artifacts that may appear
when data collection conditions a llow the system to acquire fewer than the
required encoding numbers (for example, low phase encod ing settings of 128 or
160). Choose from the fol lowing options, as shown in figure 6-133:
• off - Does not use the truncation fi Iter.
• ON- Uses the truncation fi Iter. Hitachi recommends this setting for use with
T2 FSE sequences.
• Auto- Automatically uses the truncation filter according to the number of
acquisition points.
off ON Auto
Figure 6-133. Truncation options.
Copyright© 2012 by Hitachi Medical Systems America, Inc. All rights reserved.
Note: When acquiring the S-Map data in preparation for the NATURAL option, make sure the area to be scanned is adequately covered.
Q54-53287v4
Scan Parameters 0 Shading-Filtering that corrects for signal intensity differences throughout the
image. Choose from the following options, as shown in figure 6-134:
• off- Does not use the shading con·ection filter.
• N ATURAL- Uses the shading correction with 3D sensitivity map. It is
necessary to first acquire the 3D sensitivity map using the S-Map Sequence.
• Hybrid - When used with multiple images that are scanned in the same
position (such as with Dynamic mode), the degree of correction in the first
scan is applied to later scans. When used with multiple images that are not
scanned in the same pos ition (such as 3D scans), the degree of correction is
kept constant along the sl ice direction.
• Manual - Uses the shading correction filter. The Correction parameter
(described next in this section) will be displayed.
off NATURAL Hybnd Manual
Figure 6-134. Shading options.
Correction - indicates the intensity of the shading correction. The higher the
value, the stronger the correction will be. Correction is available when Shading
is NATURAL, Hybrid or Manual. The options range from Typel to TypeS
when Shading is Hybrid or Manual. The options are off, Typel or Type2
when Shading is NATURAL (figure 6-1 35) .
*M5!Fi' Type1
Type I Type2 Type3 Type4 T e5
(a)
........
(b)
off off Type1 T e2
Figure 6-135. Correction options when Shading is (a) Hybrid or Manual and (b) NATURAL.
T2 correct.-Corrects for T2 decay that occurs with long echo train sequences.
The options are shown in figure 6-1 36.
I~EE .. iil4iilllll~to_ff ______ ~~~1 off Manual
Figure 6-136. T2 correct. options.
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Levei[% ]- Sets the level of the T2 Amp litude Correction Filter. The larger the
value, the stronger the correction. Level[%] is avai table when T2 correct. is
Manual (figure 6-137).
Figure 6-137. Level[%} and T2 Target parameters.
T2 Target- Sets the T2 value for the T2 ampl itude correction area. T2 Target
is available when T2 correct. is Manual (figure 6-137). T2 Target should be
set to match the TE value.
Adaptive F ilter - Performs fi lter processing for the scanned image (figure
6- 138). For more adaptive filter infonnation, refer to the "Review Task
Window" section of Chapter 7, "Review and Filming Functions".
BM¥11§ off ~ I '
off Sm1Sh0 Sm1Sh1 Sm1Sh2 Sm2Sh0 Sm2Sh1 Sm2Sh2 Sm3Sh0 Sm3Sh1 Sm3Sh2 Sm4Sh0 Sm4Sh1 Sm4Sh2 Min Med Max MRAMin MRAMax
Figure 6-138. Adaptive Filter options.
Edge enhance- Performs edge enhancement for the scanned image. For more
edge enhancement infom1ation , refer to the "Review Task Window" section of
Chapter 7, "Review and Filming Functions" .
MIP Image-Specifi es whether or not to create MIP reference images
automatically after the scan is finished. Choose from the following options, as
shown in figure 6-1 39:
• off- Does not create MIP reference images.
• ON-Creates MIP reference images automatically after the scan is finished.
Figure 6-139. MIP Image options.
Copyright© 2012 by Hitachi Medical Systems America, Inc. All rights reserved.
Note: When Diffusion Analysis is ON, the DW EPI sequence is vulnerable to magnetic field distortion. If homogeneity of the magnetic field is poor image degradation and artifacts may occur. To reduce this effect be sure to carry out volume shimming before starting Diffusion Tensor Imaging.
Q54-53287v4
Scan Parameters 0 When MIP Image is O N, the following parameters become available:
MJP Edge E nh.-Adjusts the quality of the MlP refe rence images that are
created. The adjustment range is from -5 to 5. The image smoothness increases
as it approaches - 5, and the image sharpness increases as it approaches 5.
MIP Dir. - Selects the view direction of MJP reference images. Choose from
the fo llowing options, as shown in figure 6-140:
• front- Creates MlP reference images viewed from the same direction as the
direction set in Slice P lane.
• AX- Creates MIP reference images viewed from the axial direction.
• COR-Creates MIP reference images viewed from the coronal direction.
• SAG - Creates MIP reference images viewed from the sagittal direction.
• SA- Creates MJP reference images viewed from the sagittal and axial directions.
• CA- Creates MI P reference images viewed from the coronal and axial directions.
• SC-Creates MIP reference images viewed from the sagittal and coronal directions.
• SCA- Creates MIP reference images viewed from the sagittal, coronal, and
axial directions.
IMF! lAX front
·t AX COR SAG SA CA sc SCA
Figure 6-140. MIP Dir. options.
For more information about MIP reference images, refer to the "Task MIP''
section of Chapter 8, "Post-Processing Functions."
Diffusion Analysis - Specifies whether or not to create di ffus ion analysis
images automatically after the scan is finished. Diffusion Analysis is available
only when Sequence is DW EPI. Choose from the following options:
• off- Does not create diffus ion analysis images automatically.
• ON - Creates diffusion analysis images automatically after the scan is
fin ished.
When Diffusion Analysis is ON, the fo llowing parameters become ava ilable:
ADC-Avai lable when MPG Dir# is Single or T race. If Single is selected,
ADC defaults to ON. If Trace is selected, the following options become
available:
• off- ADC images are not created automatica lly after scanning.
• ON- ADC images are created automatically after scanning.
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Note: The b-factor value summarizes the influence of the gradients in OWl. The higher the b-factor value, the stronger the diffusion weighting. Hitachi recommends a b-factor of 1000.
6-82
DWI tr ace-Available when MPG Dir# is Trace, Tensor6, Tensor7,
Tensor13, or Tenso r21 (optional). Choose from the following options, as shown
in figure 6= 141:
• off- OWl trace images are not created automatically after scanning.
• ON (with bO) - DWI trace images are created automatically after scanning,
inc luding bO image.
• ON (without bO) - OWl images are created automatical ly after scanning,
without bO images .
ON(without bO) •
off ON(with bO) ON(without bO)
Figure 6-141. DWI trace options.
FA ( Fractional Anisotropy)- (Associated with the Diffusion TensorSuite,
wh ich is a purchasable option.) Avai lable when MPG Dir# is Tensor6,
Tensor7, Tensor13, or Tensor21. Calculates an index FA showing the
anisotropy of diffus ion from the obtained diffusio11 tensor, and creates an FA
map reflecting an FA value. The options are;
• off- FA images are not created automatically after scanning.
• ON -FA images are created autonnatically after scanning.
MD (Mean Diffusibi lity)-(Associated with the Diffusion TensorSuite, which
is a purchasable option.) Available when MPG Dir# is Tensor6, Tensor7,
Tensor-13, or Tenso r·21 . Calculates the mean of the intrinsic values of
diffusibility and creates an image reflecting the MD. The options are:
• off- MD images are not created automatically after scann ing.
• ON-MD images are created automatically after scanning.
Figure 6-142 shows the FA and MD parameters .
. ,. '%3
Figure 6-142. FA and MD parameters.
Save Corr.Image- When Save Corr.Image is ON, the original images and the
distortion-corrected images are saved in the system database. When Save Corr.
Image is off, the corrected images are not created automatically after scanning.
Noise Threshold - Indicates a threshold value to eliminate background noise.
The range is 0 to l 00; increasing the value eliminates more noise.
Copyright© 2012 by Hitachi Medical Systems America, Inc. All rights reserved.
Note: Distortion correction settings will vaty depeflding on the body part being scanned.
Q54-53287v4
Scan Parameters 0 Correct Distortion-Specifies whether or not to correct distortion of the input
image. The options a re:
• off- Image distortion is not corrected for the FA map, MD map, and DWI
Trace images.
• ON - Image distortion is corrected for the FA map, MD map, and DWI Trace
images.
D.C.Levei- Corrects image distortion generated by nonlinearity in the gradient
magnetic field. The options are:
• off- Image distort ion is not corrected.
• Auto - The system applies distortion correction as needed.
• GC- (Gradient Correction) Distortion correction is a lways applied.
When D.C.Level is Auto or GC, Region Cut is displayed.
Region Cut- Regions that cannot be corrected by the distortion correction
function may appear on the edge of the image. Region Cut options (as fo llows)
determine whether or not the uncorrected regions are cut from the image:
• off- The regions are not cut from the image. This is the recommended option
when scanning la rge anatomical regions (such as large abdomens), to ensure
that a ll of the anatomy of interest is included.
• Auto - T he regions are cut from the image when there are regions that cannot
be corrected by the distortion correction function.
W-Widtbl - Indicates the window width of the display for one echo. The set
value becomes the default wi ndow width for displaying images. After an image
is displayed, the wi ndow width can be changed.
W-Levell - lndicates the window level of the display for one echo. The set
value becomes the default window level for displaying images. After an image
is displayed, the window level can be changed.
W-Width2- Available when Multi Echo (in the Seq. Parameter area) is 2 or
greater. Indicates the window width of the display for two echoes. This value
becomes the default window width for displaying images. After an image is
displayed, the window width can be changed.
W-Levei2 - Available when Multi Echo (in the Seq. Parameter area) is 2 or
greater. Indicates the window level of the display for two echoes. Th is value
becomes the default window level for displaying images. After an image is
displayed, the window level can be changed.
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6-84
Figure 6-143 shows the window width and level parameters.
p¥111
••• JWIIf
Figure 6-143. Window width and window level parameters.
Positioning
Positioning parameters allow you to select various options involved with the
scanning and viewing of images.
The Positioning section ofthe ScanParameterList window (figure 6-144)
contains the following parameters:
H-F
S-C-A
off
Lme
ON
off
Figure 6-144. The Positioning section of the ScanParameterList window.
Slice Ord. A -Specifies the direction in which the axial plane slices wi ll be
scanned and displayed. Choose from the following options, as shown in figure
6-145:
• H-F - From head to feet
• F-H -From feet to head
i§Hilijf H-F f--H---F-------1
F-H
Figure 6-145. Slice Ord. A options.
Copyright© 2012 by Hitachi Medical Systems America, Inc. All rights reserved.
Note: Plane Order cannot be changed, but the slice order within a plane can be.
Q54-53287v4
Scan Parameters 0 Slice Ord. S-Specifies the direction in which the sagittal plane slices will be
scanned and displayed. Choose from the following options, as shown in figure 6-1 46:
• R-L- From right to left
• L-R- From left to right
l.i.Efllflii¥41111~(R_·L~----~~J I ~-~ I
Figure 6-146. Slice Ord. S options.
Slice Ord. C-Specifies the direction in which the coronal plane s lices will be
scanned and displayed. Choose from the following options, as shown in figure
6-147:
• A-P- From anterior to posterior
• P-A- From posterior to anterior
I ~p ~I P-A _
Figure 6-14 7. Slice Ord. C options.
Plane Order - Displays the scanning order of the s lice planes. Plane Order is
for display only, it cannot be changed.
The following planes are available for display:
• AX- Axial plane
• SAG -Sagittal plane
• COR-Coronal plane
• S-A- Sagittal plane, axial plane
• S-C- Sagittal plane, coronal plane
• C-A- Coronal plane, axial plane
• S-C-A- Sagittal pane, coronal plane, axial plane
Figure 6- I 48 shows a Plane O rder of S-C-A.
l§llh9@ S-C-A
Figure 6-148. The Plane Order parameter.
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6-86
Radial Stack-Allows easier radial slice stack positioning for MRCP
exams. When Radial Stack is ON, the radial stacks move as a group, making
posit ioning at a central point easier.
To use radial stack positioning, make sure Radial Stack is ON, then enter the
number of radial stacks to be performed in the Stacks box (located in the Seq.
Parameter area of the ScanParameterList window).
Slice Allocation- [ndicates the order of slice excitation for multi-slice
scanning. Slice Allocation is available when:
• 2D/3D is 2D
• Sequence is GE, SARGE, or RSSG
• The Mode parameter of Multi Acquisition is Interleaved
As shown in figure 6-149, Slice Allocation options include:
• Default- Scans from one side of the sl ices to the other side.
• Convergence-Scans from both sides of the s lices towards the center.
[Qff4idliii!MI--'o::..::e.;..:cfau::..::k __ --t Oefauk Convergence
Figure 6-149. Slice Allocation options.
Line/Box- Specifies the manner in which 2D imaging slice lines appear when
they are displayed in the viewp01ts for positioning. Line/Box is not displayed
when 3D is selected from the 2D/3D box. The following options are available,
as shown in figure 6-150:
• Line- Displays the slice surface as a line.
• Box-Displays the sl ice surface as a box.
line Bo:<
Figure 6-150. LineiBox options.
Copyright© 2012 by Hitachi Medical Systems America, Inc. All rights reserved.
Q54-53287v4
Scan Parameters 0 Guide L ine -Specifies whether or not guidelines w ill appear when changing
s lice position or number of slices. Guide lines are the dotted lines displayed at
the top and bottom of the slice group. The fo llowing options are available:
• Yes- The dotted lines are longer than the s lice lines and continue to be
displayed when s lices are moved. Figure 6- 151 shows the results when Guide
Line is Yes.
Figure 6-151. The Guide Line parameter set to Yes.
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0AS Is~ MRI System Reference Manual 11141 htlet~t olllqHt
6-88
• No- The dotted lines are approximately the same length as the slice lines and
are displayed around the outer edges of the slice group. The dotted lines will
elongate and display during slice movement. Figure 6-152 shows the results
when Guide Line is No.
Figure 6-152. The Guide Line parameter set to No.
G.Intvl -Specifies whether or not the slice interval can be changed for each
slice stack or slab group for scans that involve multiple stacks or slabs. The
following options are available, as shown in figures 6-153 and 6-154:
• off- The slice interval for each slice or slab group can be changed. When
G.Intvl is off, the Interval box is displayed in the Scan Positioning
Information bar at the bottom of the Task View area. Figure 6- I 53 shows the
G.Intvl parameter set to off.
~~I'IMIIIIIII ~lo~ff--------~·1
Figure 6-153. G.lntvl set to off.
Copyright© 2012 by Hitachi Medical Systems America, Inc. All rights reserved.
Q54-53287v4
Scan Parameters 0 • ON - The slice intervals for each slice or slab group are set to the same value
and cannot be changed individually. When G.lntvl is ON, Interval is
displayed in the Seq. Parameter area of the ScanParameterList wi ndow.
Figure 6-154 shows the G.Intvl parameter set to ON .
•• I ON
Figure 6-154. G.lntvl set to ON.
Sync.- Specifies whether to simultaneously change all plane settings when the
settings for pos ition, angle, and slice number are changed, and multiple planes
have been selected. Sync. is available only when Slice P lane is SA, SC, CA, or
SCA. Choose from the fo llowing options, as shown in figure 6-155:
• off- Does not change the settings of all planes.
• ON -Changes the settings of all planes.
Others
1*!1 -off
off ON
Figure 6-155. Sync. options.
The Others section of the ScanPa ra meterList window contains the fo llowing
parameters:
Receiver Coil-Select the receiver coil name from the list of connectab le
receiver coils, as shown in figu re 6-156. If Receiver Coil is Auto, the receiver
coil name is recognized automatically.
~4¥-YIMif¥1111 111~~--o ______ ·~J, Auto CTL LargeJomt PI/ QD Flex Body(L) QD Flex Body(Xl.) QOHead RAPID Body RAPID Breast RAPID C.Sp1ne RAPID Foot RAPID Head RAPID Knee RAPID I# RAPID Shoulder RAPID Wrist TRBo
Figure 6-156. Receiver Coil options.
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6-90
Mod e-Specifies the receiver coil mode for multi-mode coils, such as the CT L
and RAPID Foot co ils. A mode can be selected from the Mode list that is
available for the receiver coil chosen from the Receiver Coil list , as shown in
figure 6-1 57.
RAPID Foot
Bil Ext Full
811 Ext Full Bil Ext Full Lt Bil Ext Full Rt Bil Ext Foot Bil Ext Foot U Bil Ext Foot Rt
Figure 6-157. Mode options.
If Receiver Coil is Auto, Mode changes to Auto, as shown in figure 6-158. T he
system will set the most common mode for the receiver coil that is being used.
Figure 6-158. Mode is Auto when Receiver Coil is Auto.
MorningQA- Specifies checks to be performed during the morning quality
assurance (QA) procedure. When starting the system, scanning is performed
with fixed parameters to confi rm that the system is operating correctly. All
parameters that a re current ly set are disabled, and the fi xed parameters are set.
Choose from the fo llowing options, as shown in figure 6-1 59:
• off- Does not perform MorningQA.
• GC Check - FlO-Acquires the FID (free induction decay) signal.
• GC C heck - X- Checks X-axis gradient movement.
• GC Check - Y -Checks Y-axis gradient movement.
• GC C heck - Z-Checks Z-axis gradient movement.
• Coil Check-Checks each cham1el of t he coil.
1$1,jl.i!,l,lf off
off GC Check- FlO GCCheck-X GCCheck- Y GCCheck- Z Coil Check
Figure 6-159. Morning QA options.
Copyright@ 2012 by Hitachi Medical Systems America, Inc. All rights reserved.
Note: The TIGRE measurement sequence is a fat-suppression imaging method using a fatsat pulse. To obtain the high fatsuppression effect. homogeneity of the static magnetid field is important. Therefore, be sure to carry out volume shmming prior to performing TIGRE sequence scan Utilizing the regional shimming function (available as an option) together with volume shim data can provide consistent fat suppression.
Note: With a 30 acquistion, the SNR of the images at the top and bottom edges of the slab is lower compared to that at the center region. Therefore, position the region of interest at the center of the slab and set the number of slice encodes to a slightly higher value.
Note: Hitachi recommends Circular 30 Acq. Mode with TPEAKS Echo Alloc. for all TIGRE acquisitions.
Q54-53287v4
Scan Parameters 0 Soft Sound - Specifies the Soft Sound mode, which decreases the noise level
for certa in pu lse sequences. Activation of the Soft Sound mode requires an
increase in TR, and, consequently, an increase in scan time. Choose from the
fo llowing options, as shown in figure 6-160:
• ofT - Acquisition is not performed in Soft Sound mode.
• ON-Acquisition is perfom1ed in Soft Sound mode.
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Figure 6-160. Soft Sound options.
TIGRE
The TIGRE sequence is a 30 fast, T l-weighted, RF-spoiled SARGE sequence
using a fatsat pulse. Th is sequence can be used for T l-weighted, fat-suppressed,
dynamic imaging with contrast. A segmented fatsat pulse is used to maintain
fat suppress ion and provide suffic ient temporal resolution for dynamic scans.
Shimming must be performed before the TTGRE acquisition.
The specific parameter selections that are required or recommended for TIGRE
are described below.
Sequence Area
Select the following:
• 20 /30 - Select 30.
• Sequence- Select RSSG.
Seq. Parameter Area
• Echo Alloc.-Select either Cent-Cent or Cent-Seq, as shown in figure
6-161:
Cent-Cent-Echo allocation for phase encode and slice encode directions
are both Centric. The #RF Prep value should be increased (as compared
to the Cent-Seq value) to suppress artifacts, even though this reduces the
effects of fat suppression.
Cent-Seq - Echo allocation for the phase encode direction is Centric,
while echo allocation for the slice encode direction is Sequentia l.
Figure 6-161. Seq. Parameter area settings.
6. 91
0ASJS~ MRI System Reference Manual T1Mthtr .. tllapet
Note: When 3D Acq. Mode is Circular, Slice# and Segment may be restricted.
Note: If Segment is set to an extremetly large value, longitudinal magnetization of fat is recovered and the fat suppression effect may be reduced.
6-92
• 3D Acq. Mode- When Circular is selected, Echo Alloc. is TPEAKS and the
outer corners of K-space are not acquired, which reduces scan time.
Advanced Area
For #RF P rep, Hita·chi recommends using a value of about 5 when Echo Alloc. is Cent-Seq, or a value higher than that when Echo Alloc. is Cent-Cent. This
va lue represents the number of dummy RF pulses needed to maintain the steady
state afte1· the application of the segmented fatsat pulse. Larger lilllmbers may
improve artifact suppression but a lso reduce the effect of fat suppression.
Saturation Area
Select the following, as shown in figure 6-162:
• Saturation-Select Segment FS.
• Wave- Select H-Sinc.
• RF amp.[%] -Enter 100.
• Segment- Hitachi recommends a value of about 32.
Figure 6-162. Saturation area settings.
Copyright© 2012 by Hitachi Medical Systems America, Inc. All rights reserved.