without reference, identify principles relating to diagnostic ultrasound imaging calibration with at...
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Without reference, identify principles relating to Diagnostic Ultrasound Imaging
Calibration with at least 70 percent accuracy.
DIAGNOSTIC ULTRASOUND IMAGING CALIBRATION
General Ultrasound Knowledge Other names • Real-time scanners • 2-D scanners • Duplex scanners • Echocardiographs • Cardiac ultrasound imagers • Vascular ultrasound imagers
Common uses • Cardiology • Diagnostic imaging • Obstetrics and gynecology • Ophthalmology • Radiology • Surgery • Vascular lab • Emergency department
DIAGNOSTIC ULTRASOUND IMAGING CALIBRATION
Scope • This procedure covers all diagnostic ultrasound scanners, including
general-purpose and dedicated systems • This procedure does not cover nonimaging diagnostic ultrasound
systems such as doppler blood-flow detectors and doppler fetal heart monitors
Test Equipment Required Multipurpose phantom - comprehensively evaluate the
performance of diagnostic ultrasound imaging systems with the following capabilities • Dead-zone or ring-down • Vertical and horizontal measurement calibration • Focal zone • Sensitivity • Axial and lateral resolution • Functional resolution • Grayscale and displayed dynamic range
DIAGNOSTIC ULTRASOUND IMAGING CALIBRATION
DIAGNOSTIC ULTRASOUND IMAGING CALIBRATION
• Material The phantom should be designed with a combination of monofilament
line targets and tissue-mimicking cylindrical targets of varying sizes and contrasts
The monofilament line targets should have a diameter of 0.1 mm to 0.5 mm ±5% to optimize the displayed image at frequencies typically used on general-purpose scanners
Monofilament line targets with diameters of approximately 0.5 mm should be present to optimize the displayed image at the high ultrasound frequencies typically used on small-parts scanners
Doppler flow phantom - comprehensive evaluation of ultrasound scanners that incorporate continuous-wave, pulsed-wave, or color-flow Doppler capabilities with the following capabilities: • Flow velocity • Location of flow • Directional discrimination
DIAGNOSTIC ULTRASOUND IMAGING CALIBRATION
Material The phantom can be either the tissue-mimicking type with one or more fluid-flow
channels (containing a non-degradable blood-mimicking solution with calibrated reflecting targets) or the type that incorporates a moving string target within a fluid-filled container
The string phantom provides greater accuracy for flow velocity calibration
NOTE: To check only basic Doppler operation, it is not necessary to use the calibrated
Doppler phantoms described above A less-costly blood-flow simulator may be purchased, or one may be constructed
using a fluid pump and flexible tubing submerged within a fluid-filled container In lieu of the nondegradeable blood-mimicking solution with calibrated reflecting
targets, any echogenic fluid, such as a detergent-water solution, may be used
Blood flow simulator - for checking doppler ultrasound Ecg simulator Leakage current meter Ground resistance ohmeter
DIAGNOSTIC ULTRASOUND IMAGING CALIBRATION
DIAGNOSTIC ULTRASOUND IMAGING CALIBRATION
Overview Ultrasounds typically provide 2-D images of soft tissue Scanners also provide waveforms (M-mode) Newer scanners have 3-D capabilities Ultrasound refers to sound waves emitted at frequencies above the
level of human hearing For diagnostic imaging, frequencies ranging from 2 to 10 MHz are
typically used Ultrasound waves are mechanical vibrations that require a medium for
transmission Echoes are produced whenever the beam encounters an interface of
different acoustic impedances, such as the soft-tissue/bone interface Transducer • Placed on the skin after an acoustic coupling gel is applied • Converts an electrical signal into ultrasonic energy that can be transmitted
into tissues • Reconverts reflected signal into an electrical signal
DIAGNOSTIC ULTRASOUND IMAGING CALIBRATION
Procedure Note: • Before beginning an inspection, carefully read this
procedure and the manufacturer's instruction and service manuals
• Know how to operate the equipment and the significance of each control and indicator. Also review special inspection and preventive maintenance procedures or frequencies recommended by the manufacturer
Transducer Identification and Scanner Settings for Tests with the Multipurpose Ultrasound Phantom (Record the Type, Serial #, Frequency, Settings, Power, Gain, Dynamic Range, etc.)
DIAGNOSTIC ULTRASOUND IMAGING CALIBRATION
DIAGNOSTIC ULTRASOUND IMAGING CALIBRATION
Measurements • Dead Zone - place the transducer over the dead zone line target
group. Determine the minimum distance (in mm) at which the scanner can resolve individual structures
• Axial resolution - place the transducer over one of the axial resolution line target groups. Determine the minimum reflector separation (in mm) along the axis of the transducer beam required to produce separate reflections
• Lateral resolution Place the transducer over each lateral resolution line target group Determine the minimum reflector separation (in mm) perpendicular to the
sound path needed to produce discrete reflections Because lateral resolution can vary with depth, multiple transducer
locations should be used Record the lateral resolution for each depth checked If the transducer has adjustable transmit focus, verify its operation and
perform each lateral resolution measurement in the respective focal zone, if possible
• Vertical Distance Place the transducer over a vertical distance calibration line target group Use the scanner's digital calipers and/or marker grids to determine the accuracy of
linear measurements along the axis of the transducer beam at 20 mm and 100 mm measured distances
• Horizontal Distance Place the transducer over a horizontal distance calibration line target group Use the scanner's digital calipers and/or marker grids to determine the accuracy of
linear measurements perpendicular to the sound path On images produced by flat sequenced linear-array transducers, check at 20 mm and
60 mm measured distances, using any left to right location On images produced by sector transducers, check at 20 mm and 60 mm measured
distances, but at multiple left to right positions. If the transducer has adjustable transmit focus, perform measurements within the focal zone, if possible
• Doppler Calibration If a calibrated Doppler ultrasound phantom is available, verify the accuracy of flow
velocity, directional discrimination, and, if applicable, pulsed-Doppler gate positioning Measurement parameters and display quality should not vary between inspections
with the same transducer configuration, scanner settings, and technique Operator Calibration - ensure operator calibrations are performed according
to the manufacturers manuals
DIAGNOSTIC ULTRASOUND IMAGING CALIBRATION
Other Checks Accessories
Confirm the presence and condition of accessories (e.g., transducers and coupling gel)
Verify that expiration dates have not been exceeded A copy of the instruction manual should be readily available
to the operators Chassis/housing
Examine the exterior of the scanner for cleanliness and general physical condition
Be sure that plastic housings are intact, that all hardware is present and tight, and that there are no signs of spilled liquids or other serious abuse
DIAGNOSTIC ULTRASOUND IMAGING CALIBRATION
AC plug/receptacles • Examine the AC power plug for damage • Wiggle the blades to check for security • Shake the plug and listen for rattles • If damage is suspected, open the plug and inspect it • For receptacles mounted on the scanner - verify the presence of line
power, and insert an AC plug into each and check that it is held firmly. Line cord • Inspect the cord for signs of damage • If damaged, replace the entire cord or, if the damage is near one
end, cut out the defective portion • Be sure to wire a new power cord or plug with the correct polarity
Strain reliefs • Examine the strain reliefs at both ends of the line cord • Be sure that they hold the cord securely
DIAGNOSTIC ULTRASOUND IMAGING CALIBRATION
Circuit breaker/fuse • If the scanner has a switch-type circuit breaker, check that it moves
freely • If the scanner is protected by an external fuse, check its value and type
against that marked on the chassis Cables • Inspect any cables (e.g., transducer) and their strain reliefs for general
condition • Carefully examine cables to detect breaks in the insulation and to ensure
that they are gripped securely in the connectors at each end to prevent rotation or other strain
• Verify that there are no intermittent faults by flexing electrical cables near each end and looking for erratic operation or by using an ohmmeter
Transducers • Check the surface areas of ultrasound transducers for deterioration,
cracks, or dents in the membrane • Check the acoustic fluid of mechanically steered transducers; refill with
the recommended fluid if air bubbles are present
DIAGNOSTIC ULTRASOUND IMAGING CALIBRATION
Controls/switches • Before changing any controls, check their positions • If any settings appear unusual (e.g., a gain control at
maximum), consider the possibility of inappropriate clinical use or of incipient device failure
• Record the setting of those controls that should be returned to their original positions following the inspection Physical condition Secure mounting, and correct motion Check that control knobs have not slipped on their shafts Control fixed-limit stops, alignment, as well as positive
stopping Each control and switch performs its proper function
DIAGNOSTIC ULTRASOUND IMAGING CALIBRATION
Indicators/displays • Record the reading of an hour meter, if present • During the course of the inspection, confirm the operation of all lamps,
indicators, meters, gauges, and visual displays on the scanner • Be sure that all segments of a digital display function • Observe an image on the CRT display, and check its quality Also verify
image quality of peripheral accessories Audible signals (Confirm appropriate volume, as well as the operation
of a volume control) ECG - Using an ECG simulator, verify normal operation of ultrasound
scanners configured for echocardiography, according to the following criteria: • Baseline - constant thickness; horizontal and no vertical drift • ECG waveform should be clearly visible, including the P wave and QRS
complex • 50/60 Hz noise should not be present • Intervals between the timing marks displayed by the scanner should be
consistent with the timing of the ECG simulator
DIAGNOSTIC ULTRASOUND IMAGING CALIBRATION
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