Pilot Study Comparing Patient ESE Manual vs. AEC Technique Factors

Mach 2006Bureau of Radiological Health Decision Made at Start of QA Program Test all equipment in manual mode –AEC equipment mostly found in hospitals and large radiology suites –Facilities equipped with AEC equipment required to have manual technique charts for times when AEC not functioning –NJ test phantom could not be used to simulate patient anatomy in AEC mode –Design of Victoreen 4000 meter prevents measuring exposure parameters in AEC mode

Mach 2006Bureau of Radiological Health Affect on ESE Numbers? Physicists have raised concerns that our tests do not reflect “reality” at sites using AEC exposures Bureau agreed that the time was right to re- evaluate its testing protocols for AEC radiographic machines and established a pilot study

Mach 2006Bureau of Radiological Health Goals of Study Measure ESE utilizing both manual and AEC exposure techniques Determine if there is correlation or variance in the measured ESEs

Mach 2006Bureau of Radiological Health Population of QA affected Machines 4,810 total QA affected machines (minus BD) 1,748 at Medical Offices –16 PET/CT, 172 CT=1,560 ~15% w/AEC = at Chiropractors 445 at Podiatrists 1,787 at Hospitals –658 mobile units, 9 PET/CT, 152 CT=968 ~ 90% have AEC = 871 Total AEC = 1105 machines

Mach 2006Bureau of Radiological Health Estimate of AEC Population Machines Subject to QA4,810 Estimate of Machines w/AEC1,105 Percent w/ AEC23%

Mach 2006Bureau of Radiological Health Pilot Study Testing Protocol Verify that facility has manual technique charts available for AEC units tested Ensure that radiographic machines chosen for study have functioning AEC and are stable by testing kVp, mAs and timer linearity and accuracy Evaluate ESE for AP Lumbosacral Spine exposures at 40” SID

Mach 2006Bureau of Radiological Health Testing Setup Utilized CDRH NEXT Phantom simulating 21 centimeter patient Utilized a calibrated Radcal MDH 1015-X with 10X5-6 Ion Chamber. Chamber setup 9” above the phantom to eliminate scatter affects Measured mAs, ms, mR and ESE exposures using facility provided manual techniques

Mach 2006Bureau of Radiological Health Testing Setup Repeated measurements using AEC technique factors and center sensor Four exposures were taken in each mode and average values were calculated Calculated ESE measurements in both modes and compared differences

Mach 2006Bureau of Radiological Health Photo of Testing Setup

Sample of Machine Data Collected

Mach 2006Bureau of Radiological Health Lumbar AP ESE For AEC Equipped X-ray Machines And Its Manual Technique Comparison LOCATION: DATE:1/20/2006 FACILITY #********* REG# Room A SECTIO NSYSTEM TYPE: FILM INSPECTO R:MGM A.AEC USED: YESAEC OPERATIONAL: YES B.MANUAL TECHNIQUE PRESENT: YES C.X-RAY SYSTEM CHECK SET KVP SET mA(s) SET TIME 7532n/a EXPOSURE DATA TEST #Peak kVpmRms% ms ErrormAs #VALUE!n/a #VALUE!n/a #VALUE!n/a #VALUE!n/a Avg #VALUE!0.00 COVAR0.003 xxxx#DIV/0! PASS?TRUE #VALUE!#DIV/0!

Mach 2006Bureau of Radiological Health F.MANUAL TECHNIQUE CHART TECHNIQUE CHART POSTED/ AVAILABLE? Y kVpmAsmAmS 7532n/a EXPOSURE DATA TEST #mSmR AVG COVAR QTYUNITS SFPD 100cm F 41.3cm AVG EXPOSURE760mR ESE mR

Mach 2006Bureau of Radiological Health G.AEC TECHNIQUE kVp SetNote kvp auto select EXPOSURE DATA TEST #mRmsmAs Avg COVAR QTYUNITS SFPD cm F 41.30cm AVG EXPOSURE601.25mR ESE mR H.ESE DIFFERENCE CALCULATION EXPOSURE TECHNIQUE Avg ESE Dose Differenc e % DIFFERENCE mR MANUAL TECHNIQUE xxxxxxxx xxxxxxxxxxxxx AEC

Mach 2006Bureau of Radiological Health Composition of Study 17 machines tested at four facilities 2 machines discarded from study due to malfunctioning AEC 5 machines used CR image receptors 10 machines used film systems

Mach 2006Bureau of Radiological Health Avg kVpManualAECAvg mAs ESE mR% Test #MeasuredkVp Manual AECManualAECDifference AVG Max Min Raw Data

Mach 2006Bureau of Radiological Health Summary Of Results

Mach 2006Bureau of Radiological Health Summary Data Avg kVp ManualAEC mAs ESE mR% Test #MeasuredkVp Manual AEC ManualAECDifference All AVG Max Min Film AVG Max Min CR AVG Max Min

Mach 2006Bureau of Radiological Health Summary Of Results

Mach 2006Bureau of Radiological Health

Mach 2006Bureau of Radiological Health Reasons for Variance? Manual Technique Charts Not Always Accurate –5 machines not capable of being set at recommended technique factors –3 machines varied by 5 kVp or more between manual and AEC technique settings CDRH phantom not a perfect match for manual technique evaluation –21 cm patient vs cm Techniques

Mach 2006Bureau of Radiological Health Reasons for Variance? AEC more efficient than manual techniques –For Same kVp settings, mAs was 2 to 8 times less than manual counterpart

Mach 2006Bureau of Radiological Health Where Do We Go From Here? Joint BRH/Physicist effort to improve the accuracy of manual technique charts? Joint BRH/Physicist effort to develop an AEC test protocol including valid test phantom(s)?

Mach 2006Bureau of Radiological Health BRH Preliminary Tests on Alternative Phantom Materials CDRH Phantom not ideal and not practical Suggestion from physicists and other state programs that copper or aluminum could simulate lumbar spine phantom BRH conducted abbreviated tests using two different thicknesses of copper: 2.4 mm and 2.0 mm

Mach 2006Bureau of Radiological Health Lucite2.4 mm2.0 mmLucite2.4mm2.0mmmR % Diff PhantomCu AEC PhantomCu AEC mm CU2.0mm CU Test # mAs ESE diff ESE %16% %19% %31% %59% %24% %54% %49% %37% Ave %36% Max %59% Min %16% ESE Difference Lucite vs Copper

Mach 2006Bureau of Radiological Health Summary Of Results

Mach 2006Bureau of Radiological Health

Mach 2006Bureau of Radiological Health Physicist Input Suggestions? Phantom Materials? Volunteers to Develop AEC Protocol?