Radiographic Inspections

Procedures for Digital and Procedures for Digital and Conventional Radiographic Conventional Radiographic

Imaging SystemsImaging Systems

Lee W. GoldmanLee W. Goldman

Hartford HospitalHartford Hospital

Filling in the Gap

Reasons for Rad or R/F Inspection State regulatory requirementState regulatory requirement 3rd party payer requirement3rd party payer requirement Employer expectations (see following)Employer expectations (see following) Standards of good practice (see above)Standards of good practice (see above)

It is not uncommon that “inspections” include the It is not uncommon that “inspections” include the minimum set of tests and evaluations needed to minimum set of tests and evaluations needed to fulfill the expectation or legal requirementfulfill the expectation or legal requirement (perhaps due to time constraints and priorities)(perhaps due to time constraints and priorities)

Philosophy of InspectionsThe goal of radiographic and fluoroscopic (R/F) The goal of radiographic and fluoroscopic (R/F) inspections should be to provide value by inspections should be to provide value by evaluating and (if necessary) improvingevaluating and (if necessary) improving::

radiation safetyradiation safety image quality image quality image consistencyimage consistency

This may entail going beyond commonly This may entail going beyond commonly accepted standards to striving for stricter yet accepted standards to striving for stricter yet generally achievable performance levelsgenerally achievable performance levels

Philosophy of Inspections

Accomplishing this goal require thoroughness Accomplishing this goal require thoroughness on the part of the inspecting physicist. Since on the part of the inspecting physicist. Since “time is money”, emphasis must be placed on:“time is money”, emphasis must be placed on: efficiency of inspection methodologyefficiency of inspection methodology organization of work organization of work attention to frequent problem areas attention to frequent problem areas

Sources of Requirements/GuidelinesACMPACRAAPMNCRPCriteriaRadiographic and Fluoroscopic Units

AnnualAnnualAnnualAnnualCFRVisual Inspection/generalAnnualAnnualAnnualSemiannCFRCollimation:AnnualAnnualAnnualSemiannCFRPBL (if so equiped) AnnualAnnualAnnualAnnualGrid alignment and focusing

--- --- AnnualAnnualCFRLight field illuminationAnnualAnnualAnnualAnnualCFRHalf-value LayerAnnualAnnualAnnualAnnualCFRExposure timer accuracyAnnualAnnualAnnualAnnualCFRExposure reproducibilityAnnualAnnualAnnualAnnualExposure rates (mR/mAs):AnnualAnnualAnnualAnnualCFRmA/mAs Linearity:# 0.1AnnualAnnualAnnualAnnualkVp accuracyAnnual--- NewNewFocal spot sizeAnnualAnnualAnnualAnnualCFRSID Indication AccuracyAnnualAnnualAnnualSemiannAEC (phototiming):

AnnualAnnualAnnualCFRFluoro min source-skin distanceAnnualAnnualAnnualSemiannCFRMax fluoro entrance exposure rates (EER) AnnualAnnualAnnualSemiannTypical EER measurementsAnnualAnnualAnnualSemiannSpot film exposures and rates AnnualAnnualAnnualSemiannAutomatic brightness control functionAnnualAnnualAnnualSemiannFluoro resolution and sensitivity

----AnnualAnnualSemiannFluoro/TV system lag, flare

Guidelines and Acceptance Limits Many items commonly evaluated physicists have Many items commonly evaluated physicists have

performance levels specified by the Code of performance levels specified by the Code of Federal Regulations (CFR) 21 Part 1020Federal Regulations (CFR) 21 Part 1020

For other items, recommendations from various For other items, recommendations from various organizations (AAPM, etc)are fairly consistent organizations (AAPM, etc)are fairly consistent

State law may impose stricter limits, require more State law may impose stricter limits, require more frequent evaluations and include more test itemsfrequent evaluations and include more test items

If not legally mandated, acceptance criteria may If not legally mandated, acceptance criteria may depend on environment, equipment used, etc.depend on environment, equipment used, etc.

Might recommend stricter criteria if reasonably Might recommend stricter criteria if reasonably achievable and provides appropriate benefitsachievable and provides appropriate benefits

Efficiency of Methodology Combination of tests where appropriateCombination of tests where appropriate Time saving toolsTime saving tools Minimizing cassette/film usage (trips to the Minimizing cassette/film usage (trips to the

darkroom)darkroom)

Organization of Work Concise data formsConcise data forms: : avoid multiple pagesavoid multiple pages Sensible orderSensible order:: verify detents before AEC tests verify detents before AEC tests Effective reports:Effective reports: Clear summary, recommendationsClear summary, recommendations SURVERYOR:_______________MAX mA:___________________MODEL:____________________________________

CHAM CF:__________________CHAMBER:_________________TUBE SER #:______________________________

Focal-Chamber Distance:KVP ACCURACY AND EXPOSURE (mR/mAs):

CF: EXPOSURE (mR) MEASURED KVP SELECTED TECHNIC

mR/mAsCFAVGmR-3mR-2mR-1AVGkV-3kV-2kV-1mAsSecmAkVp

60

80

100

120

Frequency of Radiographic FindingsFogGrid SIDTimerLinearReprodkVpCollimTotalYear

0%33%6%6%24%9%30%9%332003

6%35%12%3%21%6%21%18%342002

0%42%12%2%35%2%30%26%432001

0%42%5%5%32%5%24%26%382000

6%39%6%6%27%15%18%36%331999

11%29%3%3%13%3%11%39%381998

0%24%6%6%12%12%12%18%171997

8%33%0%0%17%0%29%33%241996

6%13%0%3%35%0%32%26%311995

8%8%4%4%28%8%28%28%251994

4.4%31%5.7%3.8%25%5.7%24%26%316Total:

mR/mAs (1), HVL (1), Focal Spot (1), Artifacts (2)Other:

Inspection Factors for Digital Systems Many inspection componentsMany inspection components----no differenceno difference

– kVp, mR/mAs, linearity, timer accuracy, HVL)kVp, mR/mAs, linearity, timer accuracy, HVL) For beam measurements (kVp, mR/Mas, etc) For beam measurements (kVp, mR/Mas, etc)

– Move tube off of digital receptor if possibileMove tube off of digital receptor if possibile– If not, use lead blockerIf not, use lead blocker

Some (may) require digital receptorSome (may) require digital receptor to recordto record– Collimation Collimation – Grid alignmentGrid alignment– Focal spot sizeFocal spot size– SID Indication SID Indication ---?---?

Cardboard Cassettes or ReadyPack

Radiographic Inspection Components

Visual InspectionVisual Inspection Beam Measurements (kVp, mR, HVL, etc)Beam Measurements (kVp, mR, HVL, etc) Receptor Tests: Grids, PBL, CoverageReceptor Tests: Grids, PBL, Coverage Tube Assembly Tests: Collim, Foc Spot, SIDTube Assembly Tests: Collim, Foc Spot, SID AEC (table and upright)AEC (table and upright) Darkroom Tests (if applicable)Darkroom Tests (if applicable)

Visual Inspection Visually evident deficienciesVisually evident deficiencies

often ignored/worked often ignored/worked around by staffaround by staff

Reporting deficienciesReporting deficiencies often often leads to corrective actionsleads to corrective actions

Include:Include:–Lights/LEDs workingLights/LEDs working–Proper technique indication Proper technique indication –Locks and interlocks workLocks and interlocks work–No broken/loose dials, knobsNo broken/loose dials, knobs–Any obvious electrical or Any obvious electrical or

mechanical defectsmechanical defects

X-ray Beam Measurements kVp accuracy AND reproducibilitykVp accuracy AND reproducibility Exposure rates (mR/mAs)Exposure rates (mR/mAs) mA linearitymA linearity

– Adjacent stationAdjacent station– OverallOverall

Exposure controlExposure control– Timer accuracyTimer accuracy– Timer and/or mAs linearityTimer and/or mAs linearity

ReproducibilityReproducibility Half-Value LayerHalf-Value Layer

kVp Evaluation: Significance Among most common issueAmong most common issue, ,

even with HF generators even with HF generators Poor kV calibration canPoor kV calibration can::

– Increase dose if kV’s too lowIncrease dose if kV’s too low– Cause poor mA linearity, Cause poor mA linearity,

leading to possible repeatsleading to possible repeats

Image contrast:Image contrast: affected, but affected, but relatively minor effect for relatively minor effect for ranges of miscalibration ranges of miscalibration usually encounteredusually encountered

kVpTotal

30%33200321%34200230%43200124%38200018%33199911%38199812%17199729%24199632%31199528%251994

23.7%316Total:

Causes of kV Miscalibration

Inadequate provisions for kV adjustmentsInadequate provisions for kV adjustments– May have only one overall kV adjustments to May have only one overall kV adjustments to

raise or lower all kVps and one to adjust kV rampraise or lower all kVps and one to adjust kV ramp– Result: difficult to properly calibration all stationsResult: difficult to properly calibration all stations

Miscalibrated compensation circuits:Miscalibrated compensation circuits:– Initial sags or spikes as tube begins to energizeInitial sags or spikes as tube begins to energize– May significantly affect short exposure timesMay significantly affect short exposure times

Important to evaluate kV accuracy at several Important to evaluate kV accuracy at several mA/kV combinationsmA/kV combinations, and possibly all mA’s, and possibly all mA’s..

Causes of HF kVp Miscalibration Pulse freq calibration: infrequent but seen on units Pulse freq calibration: infrequent but seen on units

invasively calibrated at generator rather than at tubeinvasively calibrated at generator rather than at tube Power line limitations: more common if powered by Power line limitations: more common if powered by

1-phase line with inadequate power 1-phase line with inadequate power Units incorporating energy storage device helpsUnits incorporating energy storage device helps

Measuring kV: Yesterday

Measuring kVp: Today

kVp Measurements (Con’t) Invasive measurementInvasive measurement::

– still standard for many service personnel)still standard for many service personnel) Non-invasive kV metersNon-invasive kV meters (highly recommended): (highly recommended):

– Measurements at many settings practical--allows Measurements at many settings practical--allows comprehensive eval of accuracy & reproducibility comprehensive eval of accuracy & reproducibility

Understand characteristicsUnderstand characteristics of your kV meterof your kV meter– Minimum exposure time for accurate measurementMinimum exposure time for accurate measurement– Accuracy ~2%: beware of imposing tight limitsAccuracy ~2%: beware of imposing tight limits– Effect of mid- or HF (meters that sample waveform)Effect of mid- or HF (meters that sample waveform)– Selection of waveform typeSelection of waveform type– Properly calibrated filtration rangeProperly calibrated filtration range

Effect of Filtration on kV Meters

Measured kVpmm addedMultiFuncMeter 2Meter 1Filtration

79.180.179.2079.282.579.82 AL79.284.881.10.1 Cu + 1 Al79.382.283.80.2 Cu + 1 Al

kVp Waveforms Obtainable with meters having computer outputObtainable with meters having computer output Very useful to recognize cause of calibration Very useful to recognize cause of calibration

problemsproblems((ramps, spikes, dropped cycles or phases)ramps, spikes, dropped cycles or phases)kV Waveform

0

10

20

30

40

50

60

70

0 10 20 30 40 50 60

milliseconds

kV

kVp: Action Limits CFR: CFR: refers only to manufacturer’s specificationsrefers only to manufacturer’s specifications Manufacturer specs: Manufacturer specs: often quite loose (eg, +/-7%) often quite loose (eg, +/-7%) Common recommendations:Common recommendations: 5% or 4-5 kV 5% or 4-5 kV For consistency:For consistency:

differences between kV calibration at different mA differences between kV calibration at different mA stations may be more important than across-the-stations may be more important than across-the-board errors: eg: board errors: eg:

100 mA --> 80 kVp measured to be 84100 mA --> 80 kVp measured to be 84200 mA --> 80 kVp measures to be 76 200 mA --> 80 kVp measures to be 76

Both may yield similar intensities at receptor!!Both may yield similar intensities at receptor!!

kVp Action Limits-Considerations Inconsistencies may be more important than Inconsistencies may be more important than

across-the-board errorsacross-the-board errors More important for multi-unit sitesMore important for multi-unit sites (technique (technique

consistency matters more)consistency matters more) Older Generators:Older Generators:

– Often difficult to accurately calibrate all mA/kV Often difficult to accurately calibrate all mA/kV – Recalibrations may shift error to other rangesRecalibrations may shift error to other ranges– More important to accurately calibrate limited More important to accurately calibrate limited

but clinically important limited rangebut clinically important limited range May attempt improvementsMay attempt improvements during next service or during next service or

during servicing for other corrective actionsduring servicing for other corrective actions

X-ray Beam Measurements kVp accuracy AND reproducibilitykVp accuracy AND reproducibility Exposure rates (mR/mAs)Exposure rates (mR/mAs) mA linearitymA linearity Exposure controlExposure control reproducibilityreproducibility Half-Value LayerHalf-Value Layer

Beam Exposure MeasurementsPROBLEM FREQUENCIESPROBLEM FREQUENCIES Poor linearity (adjacent or a Poor linearity (adjacent or a

common problemcommon problem Timer and Reproducibility Timer and Reproducibility

issues occur less frequentlyissues occur less frequently Problems may appear only:Problems may appear only:

– with certain mA settingswith certain mA settings– Under certain conditionsUnder certain conditions– At certain kV rangesAt certain kV ranges

Important to evaluate Important to evaluate many kV/mA settings!!many kV/mA settings!!

TimerLinearReproTotalYear

6%24%9%332003

3%21%6%342002

2%35%2%432001

5%32%5%382000

6%27%15%331999

3%13%3%381998

6%12%12%171997

0%17%0%241996

3%35%0%311995

4%28%8%251994

3.8%25.3%5.7%316Total:

mR/mAs (1), HVL (1)Other:

Efficient Beam Measurements Valuable to make Valuable to make both kV and exposureboth kV and exposure

measurements at many kV/mA settings.measurements at many kV/mA settings. Appropriate to measure kV and exposure Appropriate to measure kV and exposure

measurements simultaneously.measurements simultaneously. May accomplish this via:May accomplish this via:

– AppropriateAppropriate (multipe) tools and test geometry (multipe) tools and test geometry– Multifunction metersMultifunction meters

Efficient Beam Measurements

Multiple MetersMultiple Meters

Geometry with Multiple Detectors ScatterScatter from kV meter from kV meter

(or other material) can (or other material) can significantly affect significantly affect exposure measurementexposure measurement

Procedures:Procedures:– Tight collimationTight collimation

– Block scatter from Block scatter from dosimeter (air gap, dosimeter (air gap, foam spacer, lead foam spacer, lead blockerblocker

Efficient Beam Measurements

Multifunction MetersMultifunction Meters

X-ray Beam Measurements kVp accuracy AND reproducibilitykVp accuracy AND reproducibility Exposure rates (mR/mAs)Exposure rates (mR/mAs) mA linearitymA linearity Exposure controlExposure control reproducibilityreproducibility Half-Value LayerHalf-Value Layer

Exposure Rates (mR/mAs) Measure at several mA/kV settingsMeasure at several mA/kV settings covering covering

the commonly used clinical rangesthe commonly used clinical ranges– Can measure along with kVp (no add’l exposures)Can measure along with kVp (no add’l exposures)– Measure at relevant distance (eg, 30”)Measure at relevant distance (eg, 30”)

Normal ranges very broadNormal ranges very broad: : – Affected by filtration, age, kV and mA calibrationAffected by filtration, age, kV and mA calibration– Common range (30”): 12 +/- 50% (3-phase, HF)Common range (30”): 12 +/- 50% (3-phase, HF)– Narrow limits which have been published (6 Narrow limits which have been published (6

mR/mAs +/- 1 at 100 cm) are not realisticmR/mAs +/- 1 at 100 cm) are not realistic Greatest value is for patient dose estimatesGreatest value is for patient dose estimates

X-ray Beam Measurements kVp accuracy AND reproducibilitykVp accuracy AND reproducibility Exposure rates (mR/mAs)Exposure rates (mR/mAs) mA linearitymA linearity Exposure controlExposure control reproducibilityreproducibility Half-Value LayerHalf-Value Layer

Evaluating Linearity Both adjacent-station linearity as well as overall Both adjacent-station linearity as well as overall linearity (between any two mA stations) are importantlinearity (between any two mA stations) are important

mA Linearity (con’t) Definition:Definition:

L = (RL = (RmA-1 mA-1 - R- RmA-2mA-2)/(R)/(RmA-1 mA-1 + R+ RmA-2mA-2)) where where

R is mR/mAs at mA-1 and mA-2R is mR/mAs at mA-1 and mA-2 Usual Requirement:Usual Requirement: L < 0.1L < 0.1 for any pair of for any pair of

adjacent adjacent mA stationsmA stations Exposure rates may differ by ~20% yet passExposure rates may differ by ~20% yet pass Prob signif contributor to technique errorsProb signif contributor to technique errors We recommendWe recommend: : L < 0.1 for any pair of mAL < 0.1 for any pair of mA

L < 0.05 for adjacent pairsL < 0.05 for adjacent pairs

mA Linearity (con’t)

For some HF and Falling Load Generators:For some HF and Falling Load Generators: Don’t allow selection of mADon’t allow selection of mA May allow selection of load:May allow selection of load:

– 60%/80%/100%60%/80%/100%– Low/Half/Full, etc)Low/Half/Full, etc)

May evaluate linearity for different loadMay evaluate linearity for different load

Note:Note: For these (and some other HF) units, For these (and some other HF) units, linearity of mAs rather than mA may be linearity of mAs rather than mA may be more pertinentmore pertinent

X-ray Beam Measurements kVp accuracy AND reproducibilitykVp accuracy AND reproducibility Exposure rates (mR/mAs)Exposure rates (mR/mAs) mA linearitymA linearity Exposure controlExposure control

– Timer accuracyTimer accuracy– Timer or mAs linearityTimer or mAs linearity

reproducibilityreproducibility Half-Value LayerHalf-Value Layer

Timer Accuracy

Exposure Control & Timer Accuracy

Measure as part of linearity testsMeasure as part of linearity tests– Also at longer and shorter times if necessaryAlso at longer and shorter times if necessary

For HF generators:For HF generators:– exposures terminated at desired mAs, not time.exposures terminated at desired mAs, not time.– More meaningful to evaluate exposure control More meaningful to evaluate exposure control

via linearity of exposure versus mAsvia linearity of exposure versus mAs

Timer Accuracy: Action Limits 3-phase1-Phase

< 10 mSec>10 mSecManufManufManufCFR10%5%Not specifAAPM1

20%5%Not separately specifACMP2

5%5%1 pulse if >1/20 secNCRP3

0 pulses if < 1/20 sec20%5%1 pulse if >1/10 secHendeei4

0 pulses if < 1/10 sec

1- AAPM Report 74, July 20022- ACMP Report #1, Jnauary 19863 - NCRP Report 99, December 19884 - HEW Publ (FDA) 79-8094

Recommend:Recommend:– Greater attention to mAs and timer exposure linearityGreater attention to mAs and timer exposure linearity– Attention to accuracy of short exposure timesAttention to accuracy of short exposure times– Awareness of non-invasive timer characteristicsAwareness of non-invasive timer characteristics

X-ray Beam Measurements kVp accuracy AND reproducibilitykVp accuracy AND reproducibility Exposure rates (mR/mAs)Exposure rates (mR/mAs) mA linearitymA linearity Exposure controlExposure control reproducibilityreproducibility Half-Value LayerHalf-Value Layer

Reproducibility

Usual Criteria: coeff of variaton < 0.05Usual Criteria: coeff of variaton < 0.05 Our experience: Rarely a problem per seOur experience: Rarely a problem per se Causes when foundCauses when found::

– Abnormally terminated exposures (errors)Abnormally terminated exposures (errors)– Tripped circuit breakerTripped circuit breaker– Often occur only at certain technique settingsOften occur only at certain technique settings

CFR test: 10 exposures within 1 hour, CFR test: 10 exposures within 1 hour, checking line voltage prior to each exposurechecking line voltage prior to each exposure

We recommend:We recommend: limited test (3 exposures) at limited test (3 exposures) at several settings, with followup if necessaryseveral settings, with followup if necessary

X-ray Beam Measurements kVp accuracy AND reproducibilitykVp accuracy AND reproducibility Exposure rates (mR/mAs)Exposure rates (mR/mAs) mA linearitymA linearity Exposure controlExposure control Half-Value LayerHalf-Value Layer

HVL Measurement Failures do occurFailures do occur Should test new tubes Should test new tubes

prior to clinical useprior to clinical use Test procedure should Test procedure should

allow easy setup, proper allow easy setup, proper geometry (adequate geometry (adequate space between dosimeter space between dosimeter and aluminum sheetsand aluminum sheets

Measure at desired Measure at desired measured kVpmeasured kVp

Criteria from CFRCriteria from CFR

Collimation X-ray/light field congruence and alignmentX-ray/light field congruence and alignment Light field IlluminationLight field Illumination Anode cutoffAnode cutoff Damaged off-focus radiation limitersDamaged off-focus radiation limiters Positive Beam LimitationPositive Beam Limitation

Collimation: Congruence

Collimation: Congruence Simple toolsSimple tools can sufficecan suffice Relatively frequentRelatively frequent issue, issue,

particularly for portablesparticularly for portables Some uncertaintySome uncertainty in in

marking light field edgesmarking light field edges CFR Criteria:CFR Criteria: 2% of SID for 2% of SID for

L/X congruence and L/X congruence and indicator accuracy indicator accuracy (1.5” at 72” SID !!)(1.5” at 72” SID !!)

Can usually do better:Can usually do better: try try for 1% of SID congruencefor 1% of SID congruence

Light Field Illumination/Contrast CFR Specifications:CFR Specifications:

– Illum: >160 lux at 100 cmIllum: >160 lux at 100 cm– Contrast: I1/I2 > 4 (I1,I2 Contrast: I1/I2 > 4 (I1,I2

are illuminations 3 mm in are illuminations 3 mm in and out from light edge, and out from light edge, respectively)respectively)

Often never inspectedOften never inspected Common problem onCommon problem on

some collim designssome collim designs Recommend:Recommend: test if test if

visually dim or edge visually dim or edge definition is poordefinition is poor

Anode Cutoff and Off-focus Limiters

Evaluated from full-field exposures:Evaluated from full-field exposures:– both lengthwise and crosswise orientationsboth lengthwise and crosswise orientations– May combine with PBL or grid alignment testsMay combine with PBL or grid alignment tests

Anode Cutoff:Anode Cutoff: failure to reach anode edge of film failure to reach anode edge of film with adequate intensitywith adequate intensity

Off-focus limitersOff-focus limiters:: – Can become bent inward, blocking primary x-rayCan become bent inward, blocking primary x-ray

– Poorly delineated edge of x-ray field occuring Poorly delineated edge of x-ray field occuring before reaching each of image receptorbefore reaching each of image receptor

Positive Beam Limitation No longer FDA-requiredNo longer FDA-required Still available/common for non-digital systemsStill available/common for non-digital systems Test for each cassette sizeTest for each cassette size Can often use single test cassette by overriding Can often use single test cassette by overriding

PBL or switching to manual modePBL or switching to manual mode Place angled cassette on table of in front of Place angled cassette on table of in front of

receptor to capture full fieldreceptor to capture full field Limits: from CFRLimits: from CFR Common causes of Failure:Common causes of Failure:

– Mechanical failure of sensorsMechanical failure of sensors– Calibrated for metric but english sizes used, etcCalibrated for metric but english sizes used, etc

Focal Spot Size Measurement:Measurement:

–OK to use star pattern test OK to use star pattern test with digital image with digital image butbut

–difficult to properly expose difficult to properly expose with NEMA kV, mA (need with NEMA kV, mA (need lowest mAs, 1 mm Cu)lowest mAs, 1 mm Cu)

Results rarely usefulResults rarely useful Pinhole/slit tests:Pinhole/slit tests:

–Not clinically relevantNot clinically relevant–Needed to resolve failureNeeded to resolve failure

Resolution-based testResolution-based test (as in MQSA) at appropriate(as in MQSA) at appropriate distance/position could bedistance/position could be useful (limits?)useful (limits?)

SID Accuracy Measurement:Measurement:

– Location of focal spot usually not marked or visibleLocation of focal spot usually not marked or visible– Determine magnification of known-object size: Determine magnification of known-object size:

convenient to combine with star pattern f.s. testconvenient to combine with star pattern f.s. test– Digital displays: should check 2-3 distances Digital displays: should check 2-3 distances

Criteria:Criteria: 2% of SID 2% of SID Causes of failure:Causes of failure: New installations: New installations:

– incorrectly located/mounted scaleincorrectly located/mounted scale– miscalibrated digital displaymiscalibrated digital display

Causes of Failure: Existing installationsCauses of Failure: Existing installations– incorrect or mispositioned tape measureincorrect or mispositioned tape measure– Incorrectly used tape (tape handle ‘tip’ or ‘flat’)Incorrectly used tape (tape handle ‘tip’ or ‘flat’)

Grid Alignment/Appropriateness

Common problem area due to:Common problem area due to: Incorrect grid: 72” upright grid for orthopedic officeIncorrect grid: 72” upright grid for orthopedic office Angulation due to installation errors or sag (with age)Angulation due to installation errors or sag (with age) Incorrect lateral detents (table and upright receptors)Incorrect lateral detents (table and upright receptors) Stationary grid artifacts with CR (“corduroy” effect)Stationary grid artifacts with CR (“corduroy” effect)

Grid Cutoff vs Lateral Misalignment

Grid cutoff (absorption of primary x-rays) versus amount of Grid cutoff (absorption of primary x-rays) versus amount of lateral decentering of x-ray tube focal spot from the grid lateral decentering of x-ray tube focal spot from the grid focal line. Lateral decentering is relatively common due to focal line. Lateral decentering is relatively common due to misplacement or changes in detent positions misplacement or changes in detent positions (measurements are for a typical 10:1 grid, 103 lines/inch)(measurements are for a typical 10:1 grid, 103 lines/inch)

3.532.521.510.50Distance (in):92%82%71%53%41%24%12%0%% absorbed:

Stationary Grid Artifacts with CR

Problem if grid Problem if grid lines parallel to lines parallel to CR horizontal CR horizontal scan directionscan direction

Need > 65-70 Need > 65-70 lines/cm for lines/cm for clinically clinically acceptable acceptable imagesimages

Testing Grids If exposure possible with tube off lat detent:If exposure possible with tube off lat detent:

– Load cassette crosswise in receptorLoad cassette crosswise in receptor– Position x-ray at lateral detent and proper SIDPosition x-ray at lateral detent and proper SID– Expose (~3 mAs at 50 kVp) with full x-ray fieldExpose (~3 mAs at 50 kVp) with full x-ray field– Repeat with lateral shift of +/- 1” and +/-2”Repeat with lateral shift of +/- 1” and +/-2”– Can use one cassette, exposing narrow stripsCan use one cassette, exposing narrow strips– Maximum density of signal should be at detent Maximum density of signal should be at detent – Image density or signal should be rel uniform Image density or signal should be rel uniform

If cannot move off detent:If cannot move off detent: – one exposure--should have relatively uniform one exposure--should have relatively uniform

signal or density across imagesignal or density across image

Radiograpic Inspection: Summary1)1)  Visual inspection and recording of informationVisual inspection and recording of information2) kVp and mR/mAs together at 4 kVs, 3 mA’s2) kVp and mR/mAs together at 4 kVs, 3 mA’s3) mR at fixed mAs for all mA; also measure time, kVp3) mR at fixed mAs for all mA; also measure time, kVp4)4)  HVL measurementHVL measurement5)5) Light/X-ray field alignmentLight/X-ray field alignment6)6)  Star pattern focal spot test with SID verificationStar pattern focal spot test with SID verification7)7)  PBL test with film 14x17” test inspected for coveragePBL test with film 14x17” test inspected for coverage8)8)  Grid alignment (also inspected for coverage)Grid alignment (also inspected for coverage)9)9)  Table and upright receptor AEC tests (if applicable)Table and upright receptor AEC tests (if applicable)10)10)  Darkroom fog evaluation (if applicable)Darkroom fog evaluation (if applicable)11)11)  Vendor-specific digital receptor tests, if availableVendor-specific digital receptor tests, if available

Portable Radiography Inspection Battery-powered:Battery-powered:

– mR/mAs and kV mR/mAs and kV formerly frequent formerly frequent problems; rare with problems; rare with modern versionsmodern versions

Capacitor-dischargeCapacitor-discharge– More uncommonMore uncommon– Difficult to testDifficult to test

Outlet-powered and Outlet-powered and all portable typesall portable types::– Collimation most Collimation most

frequent problemfrequent problem

ReprodkVpCollimHVLTotalPorts

72003

20%20%52002

13%13%82001

11%11%11%92000

11%33%56%91999

20%30%10%101998

50%100%50%41997

67%33%33%31996

25%50%25%41995

25%25%41994

3%22%32%10%63Total:

mR/mAs (0), Reprod (0), SID (0)Other:

Linearity (NA), timer (0), Foc Spot (0)