pt. dose and the modern angiographic system

1

Patient Dose and the Modern Patient Dose and the Modern Angiographic SystemAngiographic System

Beth SchuelerBeth SchuelerMayo Clinic RochesterMayo Clinic Rochester

AAPM Annual MeetingAAPM Annual Meeting July 2010July 201022

Educational ObjectivesEducational Objectives

�� Review fluoroscopic dose quantitiesReview fluoroscopic dose quantities�� Understand the operation of kermaUnderstand the operation of kerma--area product area product

metersmeters�� Learn how to verify the accuracy of integrated Learn how to verify the accuracy of integrated

dosimetry systems in fluoroscopy equipmentdosimetry systems in fluoroscopy equipment�� Understand how to measure phantom entrance Understand how to measure phantom entrance

air kerma ratesair kerma rates�� Review factors that affect fluoroscopy dose rates Review factors that affect fluoroscopy dose rates

and image qualityand image quality

33

MotivationMotivation

�� Display and recording of patient dose for Display and recording of patient dose for fluoroscopicallyfluoroscopically--guided interventional (FGI) guided interventional (FGI) procedures allows for:procedures allows for:�� Avoidance of skin injuryAvoidance of skin injury�� Determination of whether skin injury may occurDetermination of whether skin injury may occur�� Compliance with regulations in many statesCompliance with regulations in many states

�� Measurement of dose to standardized phantoms Measurement of dose to standardized phantoms allows for:allows for:�� Determination of integrated dosimetry accuracyDetermination of integrated dosimetry accuracy�� Optimization of dose rate settings for clinical useOptimization of dose rate settings for clinical use

44

Motivation

2

55

Fluoroscopic Dose QuantitiesFluoroscopic Dose Quantities

�� Air KermaAir Kerma�� Kerma accumulated in air at a specific pointKerma accumulated in air at a specific point

�� KKa,ia,i –– incident air kerma *incident air kerma *�� Units: gray (Gy)Units: gray (Gy)�� Without backscatter Without backscatter

* ICRU Report 74, * ICRU Report 74, ““Patient Dosimetry for X Rays Used in Patient Dosimetry for X Rays Used in Medical ImagingMedical Imaging””, 2005. , 2005.

66

Air KermaAir Kerma

�� KKa,ra,r –– total air kerma at the reference total air kerma at the reference pointpoint�� Value is the total accumulated during a Value is the total accumulated during a

procedureprocedure�� Reference point is approximate location of Reference point is approximate location of

patientpatient’’s entrance surfaces entrance surface�� Defined relative to the fluoroscopy gantry by Defined relative to the fluoroscopy gantry by

IEC (2000 and 2008) and FDA (2009)IEC (2000 and 2008) and FDA (2009)

77

CC--arm Reference Point Locationarm Reference Point Location

�� 15 cm from 15 cm from isocenter toward isocenter toward xx--ray tuberay tube

�� Note that a Note that a manufacturer manufacturer may specify a may specify a different different reference point reference point locationlocation

IsocenterIsocenter

88

Other System Reference Point LocationsOther System Reference Point Locations

�� Undertable xUndertable x--ray tube:ray tube:�� 1 cm above the tabletop1 cm above the tabletop

�� Overtable xOvertable x--ray tube:ray tube:�� 30 cm above tabletop30 cm above tabletop�� XX--ray tube in lowest position possibleray tube in lowest position possible

�� Lateral type:Lateral type:�� 15 cm from table centerline toward x15 cm from table centerline toward x--ray tuberay tube�� XX--ray tube in closest positionray tube in closest position

3

99

Air KermaAir Kerma--Area ProductArea Product

�� PPKAKA -- Air kerma Air kerma ×× xx--ray beam arearay beam area�� Units: GyUnits: Gy--cmcm22

�� Value is the total accumulated during a Value is the total accumulated during a procedureprocedure

�� Without backscatterWithout backscatter�� Beam area is determined in a plane Beam area is determined in a plane

perpendicular to the central beam axisperpendicular to the central beam axis�� Variations in air kerma over the beam area Variations in air kerma over the beam area

are averagedare averaged

1010

Air KermaAir Kerma--Area ProductArea Product

�� PPKAKA is the same value at any distance from is the same value at any distance from the xthe x--ray sourceray source

AA11/A/A22 = (d= (d11/d/d22))22

KK11/K/K22 = (d= (d22/d/d11))22

dd11

dd22

AA11

AA22

1111

Peak Skin DosePeak Skin Dose

�� DDskin,maxskin,max –– Dose to the most highlyDose to the most highly--irradiated irradiated local area of skin, includes backscatterlocal area of skin, includes backscatter

�� Corrections needed to estimate Corrections needed to estimate DDskin,maxskin,maxfromfrom KKa,ra,r::�� BackscatterBackscatter�� Actual sourceActual source--skin entrance distanceskin entrance distance�� Table and pad attenuationTable and pad attenuation�� Mass attenuation coefficient ratio air: tissueMass attenuation coefficient ratio air: tissue�� Account for movement of the xAccount for movement of the x--ray beamray beam�� Addl. discussion in Addl. discussion in Tues,ThursTues,Thurs R/F CE sessionsR/F CE sessions

1212

Regulations: FDARegulations: FDA

�� 21 CFR Part 1020.32: Performance 21 CFR Part 1020.32: Performance standards for ionizing radiation emitting standards for ionizing radiation emitting products. Fluoroscopy equipment. (2009)products. Fluoroscopy equipment. (2009)

�� For fluoroscopes manufactured after June For fluoroscopes manufactured after June 2006:2006:�� Display of Display of KKa,ra,r (mGy) and(mGy) and KKa,ra,r rate (mGy/min) rate (mGy/min)

at the operatorat the operator’’s working positions working position�� Note Note PPKA KA is not requiredis not required

4

1313

Regulations: IECRegulations: IEC

�� IEC 60601IEC 60601--22--43: Particular Requirements 43: Particular Requirements for the Safety of Xfor the Safety of X--Ray Equipment for Ray Equipment for Interventional Procedures (2000) and 2Interventional Procedures (2000) and 2ndnd

edition (2010)edition (2010)�� Display of Display of KKa,ra,r (mGy) and(mGy) and KKa,ra,r rate (mGy/min) rate (mGy/min)

at the operatorat the operator’’s working positions working position�� Display of Display of PPKAKA

�� need not be at the operatorneed not be at the operator’’s working positions working position

1414

Example Integrated Dosimetry DisplaysExample Integrated Dosimetry Displays

In RoomIn Room On control consoleOn control console

1515

DICOM Dose Structured ReportDICOM Dose Structured Report

�� Includes fields for dosimetry system informationIncludes fields for dosimetry system information

1616

KermaKerma--Area Product UnitsArea Product Units

�� Be aware that the units for Be aware that the units for PPKAKA from from integrated dosimetry systems vary with integrated dosimetry systems vary with manufacturer and software revision:manufacturer and software revision:�� mGymGy--cmcm22

�� µµGyGy--mm22

�� cGycGy--cmcm22

�� dGydGy--cmcm22

�� GyGy--cmcm22

�� mGymGy--mm22

�� IEC 60601IEC 60601--22--43 243 2ndnd edition specifies Gyedition specifies Gy--cmcm22

5

1717

Integrated Dosimetry MethodsIntegrated Dosimetry Methods

�� Various methods for determining Various methods for determining KKa,ra,r and and PPKAKA are in use:are in use:

1.1. PPKAKA meter with calculation of meter with calculation of KKa,r a,r from area from area determined by known collimator positionsdetermined by known collimator positions

2.2. PPKAKA--KKa,ra,r dual chamber meterdual chamber meter3.3. Calculation of Calculation of KKa,r a,r from kVp, from kVp, mA(smA(s) and pre) and pre--

determined air kerma output values, with determined air kerma output values, with calculation of calculation of PPKA KA from known collimator from known collimator positions positions

1818

PPKAKA MeterMeter

�� Transmission, Transmission, parallel plate parallel plate ionization chamberionization chamber

�� Not visible in the Not visible in the imageimage

�� Transparent to Transparent to allow for light field allow for light field useuse

1919

PPKAKA MeterMeter

�� Mounted on Mounted on collimator housingcollimator housing�� Since Since PPKAKA is the is the

same at any same at any distance from the distance from the xx--ray sourceray source

�� Covers the entire Covers the entire xx--ray beam arearay beam area

2020

PPKAKA--KKa,ra,r Dual Chamber Meter Dual Chamber Meter

�� PPKAKA meter with a small air kerma meter with a small air kerma measurement area in centermeasurement area in center�� Mounted in the same mannerMounted in the same manner�� Air kerma value at the reference point is Air kerma value at the reference point is

determined by inverse square distance determined by inverse square distance correctioncorrection

�� Tracking of collimator positions not neededTracking of collimator positions not needed�� Measures Measures KKa,r a,r at the center of the beamat the center of the beam

�� Instead of beam average when exposure is not Instead of beam average when exposure is not uniformuniform

6

2121

Use of Wedge FiltersUse of Wedge Filters

2222

Use of Wedge FiltersUse of Wedge Filters

�� Wedge filters (equalization filters) are Wedge filters (equalization filters) are located in front of the located in front of the PPKAKA metermeter

�� Locations are typically not tracked like the Locations are typically not tracked like the collimator locations used to define the collimator locations used to define the irradiated field sizeirradiated field size

�� For integrated dosimetry using a For integrated dosimetry using a PPKAKAmeter, when wedge filters are used:meter, when wedge filters are used:�� PPKAKA value is averaged over beam areavalue is averaged over beam area�� KKa,ra,r will be underestimatedwill be underestimated

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and image qualityand image quality2424

Integrated Dosimetry System ValidationIntegrated Dosimetry System Validation

�� Laboratory conditions used to calibrate Laboratory conditions used to calibrate PPKAKAmeters will vary from clinical conditions meters will vary from clinical conditions �� Value is affected by scattered and extraValue is affected by scattered and extra--focal focal

radiation, which vary with xradiation, which vary with x--ray tube, ray tube, PPKAKAmeter position and xmeter position and x--ray energyray energy

�� Accuracy of integrated dosimetry systems Accuracy of integrated dosimetry systems should be verified under clinical conditions should be verified under clinical conditions �� Initially and after service affecting dose Initially and after service affecting dose

monitoring (e.g. monitoring (e.g. PPKAKA meter or xmeter or x--ray tube ray tube replacement)replacement)

7

2525


�� Method described here was adopted from Method described here was adopted from the RADthe RAD--IR Study *IR Study *

�� RADRAD--IR study IR study �� Patient dose data was recorded for over 2,000 Patient dose data was recorded for over 2,000

interventional radiology procedures over 3 interventional radiology procedures over 3 years at 7 facilities with 16 imaging planesyears at 7 facilities with 16 imaging planes

�� Protocol developed to validate consistency Protocol developed to validate consistency and accuracy of and accuracy of PPKAKA and and KKa,r a,r readoutreadout

* * BalterBalter et al, JVIR 2004; 15:909et al, JVIR 2004; 15:9092626

MaterialsMaterials

�� PMMA attenuator blocksPMMA attenuator blocks�� At least 25 x 25 cm to fully cover the beam At least 25 x 25 cm to fully cover the beam

field of view at the image receptorfield of view at the image receptor�� Sheets to make up 10, 20 and 30 cm Sheets to make up 10, 20 and 30 cm

thicknessesthicknesses

�� Field size measuring plateField size measuring plate�� Ionization chamber dosimeter and holderIonization chamber dosimeter and holder�� Tape measureTape measure

2727

Dosimeter SelectionDosimeter Selection

�� Ionization chamber is recommendedIonization chamber is recommended�� Provides a flat energy response over a wide xProvides a flat energy response over a wide x--

ray energy rangeray energy range�� For solid state detectors withFor solid state detectors with

energy compensation, there energy compensation, there are no NIST specified are no NIST specified calibration beams that match calibration beams that match the typical Cuthe typical Cu--filtered filtered interventional fluoroscopy interventional fluoroscopy beambeam

2828

MethodsMethods

�� Determine the sourceDetermine the source--toto--isocenter isocenter distance for the Cdistance for the C--arm to be testedarm to be tested�� From manufacturerFrom manufacturer’’s specifications ors specifications or�� Manually by positioning an object so that it is Manually by positioning an object so that it is

centered in both vertical and horizontal centered in both vertical and horizontal projections of the Cprojections of the C--armarm

�� Note that isocenter locations vary, e.g.Note that isocenter locations vary, e.g.�� Siemens Artis and Philips Allura : 75 cmSiemens Artis and Philips Allura : 75 cm�� Multistar: 80 cm, Siemens Artis Zee: 78.5 cmMultistar: 80 cm, Siemens Artis Zee: 78.5 cm

8

2929

MethodsMethods

�� Determine the location of the reference Determine the location of the reference point for the Cpoint for the C--arm to be testedarm to be tested�� From the manufacturerFrom the manufacturer’’s specifications or s specifications or �� Assume the FDA/IEC definition of 15 cm from Assume the FDA/IEC definition of 15 cm from

isocenter toward the xisocenter toward the x--ray sourceray source

3030

MethodsMethods

�� Position the CPosition the C--arm horizontallyarm horizontally�� Use maximum SIDUse maximum SID�� 30 cm PMMA next to image receptor on the 30 cm PMMA next to image receptor on the

tabletoptabletop

�� Position the field size measuring platePosition the field size measuring plate�� Perpendicular to and centered on the central Perpendicular to and centered on the central

beam axis andbeam axis and�� At the reference pointAt the reference point

3131

MethodsMethods

3232

MethodsMethods

�� Select the medium Select the medium FOV mode and FOV mode and collimate to an collimate to an approximately 10 x approximately 10 x 10 cm field10 cm field

�� Record the actual Record the actual field dimensions to field dimensions to determine determine irradiated areairradiated area

9

3333

MethodsMethods

�� Remove the field size measuring plate and Remove the field size measuring plate and place the dosimeter probe at the reference place the dosimeter probe at the reference point locationpoint location

3434

MethodsMethods

�� Record initial Record initial PPKAKA and and KKa,ra,r readingsreadings�� Fluoro using dose accumulate mode on Fluoro using dose accumulate mode on

dosimeter until accumulated air kerma is at least dosimeter until accumulated air kerma is at least 100 mGy100 mGy

�� Record final Record final PPKAKA and and KKa,ra,r readings and calculate readings and calculate differencedifference

�� Multiply probe air kerma by irradiated area to Multiply probe air kerma by irradiated area to determine probe air kermadetermine probe air kerma--area productarea product

�� Compare probe readings with integrated Compare probe readings with integrated dosimetry values for dosimetry values for PPKAKA and and KKa,ra,r

3535

MethodsMethods

�� Repeat air kerma measurement for cine or Repeat air kerma measurement for cine or digital acquisition modedigital acquisition mode

�� Remove 10 cm PMMA without moving the Remove 10 cm PMMA without moving the dosimeter probedosimeter probe�� Repeat fluoro and acquisition dose Repeat fluoro and acquisition dose

measurements with 20 cm PMMAmeasurements with 20 cm PMMA

�� Remove 10 cm more PMMA and repeatRemove 10 cm more PMMA and repeat

3636

Control LimitsControl Limits

�� FDA(2009)FDA(2009)�� KKa,r a,r shall not deviate > shall not deviate > ±± 35% for > 100 mGy35% for > 100 mGy

�� IEC(2000)IEC(2000)�� KKa,r a,r shall not deviate > shall not deviate > ±± 50% for > 100 mGy50% for > 100 mGy�� PPKA KA shall not deviate > shall not deviate > ±± 50% for > 2.5 Gy50% for > 2.5 Gy--cmcm22

�� IEC(2010)IEC(2010)�� KKa,r a,r shall not deviate > shall not deviate > ±± 35% for > 100 mGy35% for > 100 mGy�� PPKA KA shall not deviate > shall not deviate > ±± 35% for > 2.5 Gy35% for > 2.5 Gy--cmcm22

10

3737

Measurement AccuracyMeasurement Accuracy

�� Uncertainty in external dose measurementsUncertainty in external dose measurements�� Uncertainty in probe readout (Uncertainty in probe readout (±±5%)5%)�� Error in probe position (Error in probe position (±±2 mm or 3%)2 mm or 3%)�� Error in irradiated area (Error in irradiated area (±±2 mm per side or 3%)2 mm per side or 3%)

�� Total uncertainty forTotal uncertainty for KKa,ra,r : : ±±6%6%

�� Total uncertainty forTotal uncertainty for PPKA KA : : ±±7%7%

3838


�� Alternative method using an external Alternative method using an external PPKAKAmeter:meter:�� Place at least 20 cm from collimator to avoid Place at least 20 cm from collimator to avoid

scatterscatter�� Select xSelect x--ray beam size to be completely within ray beam size to be completely within

the external ionization chamberthe external ionization chamber�� Use a Use a PPKAKA--KKa,ra,r dual chamber meter to dual chamber meter to

simultaneously measure simultaneously measure KKa,ra,r valuesvalues

3939

Field Adjustment of Field Adjustment of PPKAKA and and KKa,ra,r

�� Some manufacturers provide a method of Some manufacturers provide a method of adjusting adjusting PPKAKA and and KKa,ra,r values on individual values on individual imaging systems in the fieldimaging systems in the field�� Manual adjustment (older models only)Manual adjustment (older models only)�� Software calibrationSoftware calibration

�� If no field adjustment is possible, a If no field adjustment is possible, a correction factor for correction factor for PPKAKA and and KKa,ra,r values values can be calculated as the integrated can be calculated as the integrated dosimetry system readout to probe ratiodosimetry system readout to probe ratio

4040


�� Clinical implementationClinical implementation�� Validation procedure has been used at our Validation procedure has been used at our

facility to test 11 Cfacility to test 11 C--arm imaging planes arm imaging planes annually for the past 7 yearsannually for the past 7 years

�� Includes 2 fluoroscopy system manufacturers Includes 2 fluoroscopy system manufacturers and 5 equipment modelsand 5 equipment models

11

4141

KKa,ra,r Correction FactorCorrection Factor

010203040506070

0.80

0.85

0.90

0.95

1.00

1.05

1.10

1.15

1.20

1.25

1.30

1.35

1.40

System:Probe

Freq

uenc

y

Min: 0.8Min: 0.8 Max: 1.34Max: 1.34

4242

KKa,ra,r Consistency Over TimeConsistency Over Time

020406080

100120140160

0.80

0.85

0.90

0.95

1.00

1.05

1.10

1.15

1.20

1.25

1.30

1.35

1.40

Normalized Air Kerma

Freq

uenc

y

95% CI: 0.0195% CI: 0.01

4343


�� ResultsResults�� System dose readout error found to be System dose readout error found to be

quite high (quite high (--20% to 20% to +34%)+34%)�� Dose readout is relatively consistent over Dose readout is relatively consistent over

7 year period7 year period

4444

Table and Pad AttenuationTable and Pad Attenuation

�� Note that some manufacturers include table Note that some manufacturers include table attenuation in attenuation in PPKAKA and and KKa,ra,r readout valuesreadout values

�� One manufacturer applies a correction factor One manufacturer applies a correction factor weighted for xweighted for x--ray tube underray tube under--table and table and overover--table/lateral angulation:table/lateral angulation:�� Table attenuation 0.86, 50%/50% under/overTable attenuation 0.86, 50%/50% under/over--

table use assumedtable use assumed�� Therefore, Therefore, probe:systemprobe:system ratio expected is 0.93 ratio expected is 0.93

using protocol described aboveusing protocol described above

12

4545


�� To perform skin dose estimates from To perform skin dose estimates from KKa,ra,r values, a correction for table and values, a correction for table and pad attenuation should be includedpad attenuation should be included�� Alternatively, the integrated dosimetry Alternatively, the integrated dosimetry

system readout can be calibrated to system readout can be calibrated to include table and pad attenuation if the xinclude table and pad attenuation if the x--ray tube is generally under the table ray tube is generally under the table clinicallyclinically

4646


�� Typical table and standard pad attenuation Typical table and standard pad attenuation factor is 0.7 factor is 0.7 -- 0.80.8

�� Heavily attenuating pads (gel pads) can be Heavily attenuating pads (gel pads) can be as high as 0.5 *as high as 0.5 *

* * GeiserGeiser, Huda and , Huda and Gkanatsios, Medical Gkanatsios, Medical Physics 1997Physics 1997

4747

Integrated Dosimetry SystemsIntegrated Dosimetry Systems

�� Additional information and guidance is Additional information and guidance is comingcoming

�� AAPM Task Group 190: Accuracy and AAPM Task Group 190: Accuracy and Calibration of DAP meters in Diagnostic Calibration of DAP meters in Diagnostic Radiology Radiology �� Chair: PeiChair: Pei--Jan P. LinJan P. Lin�� Charge: Charge:

�� Develop integrated dosimetry evaluation protocolDevelop integrated dosimetry evaluation protocol�� Survey clinical fluoroscopic equipment: accuracy Survey clinical fluoroscopic equipment: accuracy

and calibration methodsand calibration methods4848







13

4949

Phantom Air Kerma RatePhantom Air Kerma Rate

�� Why measure phantom fluoroscopy Why measure phantom fluoroscopy entranceentrance--surface air kerma rate (EAKR)?surface air kerma rate (EAKR)?�� Verify appropriate dose rates are available Verify appropriate dose rates are available

when acceptance testing new equipmentwhen acceptance testing new equipment�� Compare to other equipment Compare to other equipment �� Compare to benchmark valuesCompare to benchmark values�� Quality control monitoring of equipment Quality control monitoring of equipment

performanceperformance

5050

EAKR MeasurementEAKR Measurement

�� Use clinical exposure conditionsUse clinical exposure conditions�� PatientPatient--equivalent attenuator (produces an equivalent attenuator (produces an

exit beam with adequate scatter)exit beam with adequate scatter)�� Range of phantom thicknessesRange of phantom thicknesses�� Clinical sourceClinical source--toto--image receptor distanceimage receptor distance

5151

MaterialsMaterials

�� PMMA attenuator blocksPMMA attenuator blocks�� At least 25 x 25 cm to fully cover the beam At least 25 x 25 cm to fully cover the beam

field of view at the image receptorfield of view at the image receptor�� Sheets to make up 10, 20 and 30 cm Sheets to make up 10, 20 and 30 cm

thicknessesthicknesses

�� Ionization chamber dosimeterIonization chamber dosimeter�� Tape measureTape measure

5252

MethodsMethods

�� Use 10 cm air gap Use 10 cm air gap between phantom between phantom and image receptor, and image receptor, adjust SID for each adjust SID for each thicknessthickness

�� Measure EAKR for all Measure EAKR for all magnification modes magnification modes and all clinicallyand all clinically--used used dose modesdose modes

10 cm10 cm

14

5353

Benchmark EAKR ValuesBenchmark EAKR Values

�� From survey of 41 fluoroscopy systems, From survey of 41 fluoroscopy systems, mean (quartiles) EAKR for 15mean (quartiles) EAKR for 15--18 cm FOV *:18 cm FOV *:�� 20 cm thickness 20 cm thickness –– 26 (1426 (14--38) mGy/min38) mGy/min�� 30 cm thickness 30 cm thickness –– 110 (67110 (67--150) mGy/min 150) mGy/min

�� Additional benchmark data is neededAdditional benchmark data is needed�� CRCPD NEXT Cardiac Catheterization results will CRCPD NEXT Cardiac Catheterization results will

be available soonbe available soon

* * LaskeyLaskey, , WondrowWondrow, Holmes, Variability in fluoroscopic , Holmes, Variability in fluoroscopic xx--ray exposure in contemporary cardiac cath lab, JACC 2006ray exposure in contemporary cardiac cath lab, JACC 2006

5454







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Fluoroscopy Mode OptionsFluoroscopy Mode Options

�� Modern fluoroscopy units include multiple Modern fluoroscopy units include multiple optional modesoptional modes

�� Parameter selection can significantly affect Parameter selection can significantly affect dose rates and image qualitydose rates and image quality

�� Adjustments in parameter selection may Adjustments in parameter selection may be needed when measured dose rates are be needed when measured dose rates are above 75above 75thth percentile benchmark valuespercentile benchmark values

5656


�� Several different dose modes should be Several different dose modes should be available for selection by the operatoravailable for selection by the operator�� Low: for positioning fluoro, high contrast Low: for positioning fluoro, high contrast

object placement and sensitive patientsobject placement and sensitive patients�� Medium: for routine workMedium: for routine work�� High: for selective use in difficult imaging High: for selective use in difficult imaging

conditionsconditions

15

5757


�� Variable rate pulsed fluoroscopyVariable rate pulsed fluoroscopy�� Spectral beam filtrationSpectral beam filtration�� kVp selectionkVp selection�� Automatic dose rate control algorithmsAutomatic dose rate control algorithms�� Image processingImage processing

5858

Spectral Beam FiltrationSpectral Beam Filtration

�� Extra filtration added to reduce low Extra filtration added to reduce low energy xenergy x--rays absorbed in patient rays absorbed in patient tissuetissue�� Copper (Cu) is most commonCopper (Cu) is most common�� Tantalum (Ta) is also usedTantalum (Ta) is also used

�� Reduces patient entrance air kerma Reduces patient entrance air kerma raterate

�� Minimal effect on image qualityMinimal effect on image quality

5959


0

1

2

3

4

5

6

0 20 40 60 80

X-ray Energy (keV)

No

. of

X-r

ays

(X 1

0000

)

0 mm Cu 0.3 mm Cu 0.6 mm Cu 0.9 mm Cu 6060


0

10

20

30

40

50

0 0.1 0.2 0.3 0.4 0.5

Beam Filtration (mm Cu)

EA

KR

(m

Gy/

min

)

16

6161


�� Optimum filtration thickness depends on Optimum filtration thickness depends on patient attenuationpatient attenuation�� More filtration for smaller patients and body More filtration for smaller patients and body

partsparts�� Less filtration for thicker patients to avoid Less filtration for thicker patients to avoid

tube overheatingtube overheating

�� Requires use of higher mA for adequate Requires use of higher mA for adequate penetrationpenetration

6262

kVp SelectionkVp Selection

�� Increase from 70 to 80 kVp decreases entranceIncrease from 70 to 80 kVp decreases entrance--surface air kerma rate by 33%surface air kerma rate by 33%�� Disadvantage: Contrast decreases alsoDisadvantage: Contrast decreases also

0

10

20

30

40

50

60

70 kVp 80 kVp

EA

KR

(m

Gy/

min

)

6363

Automatic Dose Rate ControlAutomatic Dose Rate Control

�� Automatic variation in kVp, mA, Automatic variation in kVp, mA, pulsewidth and filtration thicknesspulsewidth and filtration thickness

�� Different algorithms are available to Different algorithms are available to optimize fluoroscopic image quality for optimize fluoroscopic image quality for different procedure types, body parts, different procedure types, body parts, pediatricspediatrics

6464

Automatic Automatic Dose Dose Rate Rate

ControlControl

Reference: Lin, Reference: Lin, Medical Physics Medical Physics 20072007

17

6565

Image ProcessingImage Processing

�� Allows partial retrieval of image quality Allows partial retrieval of image quality loss from use of dose reduction optionsloss from use of dose reduction options

�� Includes:Includes:�� Video frame averagingVideo frame averaging�� Edge enhancementEdge enhancement�� Contrast enhancementContrast enhancement

6666

ConclusionsConclusions�� Validation of the accuracy of air kermaValidation of the accuracy of air kerma--

area product and reference point air area product and reference point air kerma display values is recommendedkerma display values is recommended

�� Measurement of fluoroscopy phantom Measurement of fluoroscopy phantom entranceentrance--surface air kerma rate is a surface air kerma rate is a valuable way to optimize and benchmark valuable way to optimize and benchmark performanceperformance

6767

References (1)� Balter S, BA Schueler, DL Miller, et al. Radiation Dose in Interventional

Radiology Procedures: The RAD-IR Study: Part III: Dosimetric Performance of the Interventional Fluoroscopy Units, JVIR 2004; 15:919.

� Digital Imaging and Communications in Medicine (DICOM) Supplement 94 Diagnostic X-Ray Radiation Dose Reporting (Dose SR) (2005).

� FDA (2009) Performance standards for ionizing radiation emittingproducts. Fluoroscopy equipment, 21 CFR Part 1020.32.

� Geiser WR, W Huda, NA Gkanatsios, Effect of patient support pads on image quality and dose in fluoroscopy, Medical Physics 1997; 24:377.

� ICRU (2005) Report 74, Patient Dosimetry for X Rays Used in Medical Imaging, ICRU 5(2).

� IEC (2000) Part 2-43: Particular Requirements for the Safety of X-Ray Equipment for Interventional Procedures, IEC 60601-2-43.

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References (2)� IEC (2008) Part 1-3: General Requirements for Basic Safety and

Essential Performance – Collateral Standard: Radiation Protection in Diagnostic X-Ray Equipment, IEC 60601-1-3.

� IEC (2010). Part 2-43: Particular Requirements for the Basic Safety and Essential Performance of X-Ray Equipment for Interventional Procedures, IEC 60601-2-43, ed. 2.0 .

� Laskey WK, M Wondrow, DR Holmes, Variability in fluoroscopic x-ray exposure in contemporary cardiac catheterization laboratories, JACC 2006; 48:1361.

� Lin PP, The operation logic of automatic dose control of fluoroscopy system in conjunction with spectral shaping filters, Medical Physics 2007; 34:3169.

pt. dose and the modern angiographic system

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