Pilot Study Comparing Patient ESE Manual vs. AEC Technique Factors.

Pilot StudyComparing Patient ESE

Manual vs. AEC

Technique Factors

Mach 2006 Bureau 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


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


Goals of Study

• Measure ESE utilizing both manual and AEC exposure techniques

• Determine if there is correlation or variance in the measured ESEs


Estimate of AEC Population

Machines Subject to QA 4,810

Estimate of Machines w/AEC 1,105

Percent w/ AEC 23%


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


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


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


Photo of Testing Setup

Sample of Machine DataCollected


Lumbar AP ESE For AEC Equipped X-ray Machines

And Its Manual Technique Comparison

LOCATION: DATE: 1/20/2006

FACILITY # ********* REG# 706839

Room A

SECTION SYSTEM TYPE: FILM

INSPECTOR: MGM

A. AEC USED: YES AEC OPERATIONAL: YES

B. MANUAL TECHNIQUE PRESENT: YES

C. X-RAY SYSTEM CHECK

SET KVPSET mA(s)

SET TIME

75 32 n/a

EXPOSURE DATA

TEST # Peak kVp mR ms % ms Error mAs

1 73.14 400.900 46.0 #VALUE! n/a

2 73.47 403.000 45.8 #VALUE! n/a

3 73.74 403.000 46.1 #VALUE! n/a

4 73.50 403.000 45.8 #VALUE! n/a

Avg 73.46 402.475 45.9 #VALUE! 0.00

COVAR 0.003 0.0030.00

3 xxxx #DIV/0!

PASS? TRUE TRUETRU

E #VALUE! #DIV/0!


F. MANUAL TECHNIQUE CHART

TECHNIQUE CHART POSTED/ AVAILABLE? Y

kVp mAs mA mS

75 32 n/a n/a

EXPOSURE DATA

TEST # mS mR

1 45.7 760

2 45.4 759

3 45.5 761

4 45.9 760

AVG 45.625 760

COVAR 0.005 0.001

QTY UNITS

SFPD 100 cm

F 41.3 cm

AVG EXPOSURE 760 mR

ESE 441.68 mR


G. AEC TECHNIQUE

kVp Set Note

75 80 kvp auto select

EXPOSURE DATA

TEST # mR ms mAs

1 583.00 46.6 24.8

2 606.00 49.1 25.7

3 602.00 48.4 25.6

4 614.00 49.6 26.1

Avg 601.25 48.425 25.55

COVAR 0.02 0.027 0.021

QTY UNITS

SFPD 100.00 cm

F 41.30 cm

AVG EXPOSURE 601.25 mR

ESE 349.42 mR

H. ESE DIFFERENCE CALCULATION

EXPOSURE TECHNIQUE

Avg ESE Dose

Difference

% DIFFERENCE

mR mR

MANUAL TECHNIQUE 441.68xxxxxxxxxx xxxxxxxxxxx

AEC 349.42 92.26 20.89


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


Avg kVp Manual AEC Avg mAs Avg mAs ESE ESE mR %

Test # Measured kVp kVp Manual AEC Manual AEC Difference Difference

1 75.5 75.0 75.0 32.0 10.5 520.4 185.5 334.9 64.4

2 76.4 75.0 75.0 32.0 18.8 543.0 322.7 220.3 40.6

3 77.3 75.0 75.0 25.0 16.1 301.8 194.8 106.9 35.4

4 73.5 75.0 75.0 32.0 25.6 441.7 349.4 92.3 20.9

5 73.6 75.0 75.0 32.0 21.1 520.7 278.7 242.1 46.5

6 76.5 75.0 75.0 40.0 13.0 580.9 189.9 391.0 67.3

7 70.8 75.0 75.0 50.0 33.7 442.7 262.8 179.9 40.6

8 78.4 76.0 76.0 64.0 8.4 895.0 107.4 787.6 88.0

9 75.6 76.0 76.0 40.0 13.3 947.3 198.3 749.0 79.1

10 76.2 76.0 76.0 40.0 15.5 639.3 239.3 400.0 62.6

11 77.3 76.0 76.0 40.0 26.7 402.4 261.2 141.2 35.1

12 69.8 75.0 75.0 50.0 28.8 412.3 243.7 168.7 40.9

13 76.8 75.0 75.0 25.0 14.5 350.8 199.4 151.3 43.1

14 77.4 76.0 76.0 50.0 12.1 561.1 134.1 427.0 76.1

15 72.7 70.0 70.0 50.0 33.6 531.8 360.8 171.0 32.2

AVG 75.2 75.0 75.0 40.1 19.4 539.4 235.2 304.2 51.5

Max 78.4 76.0 76.0 64.0 33.7 947.3 360.8 787.6 88.0

Min 69.8 70.0 70.0 25.0 8.4 301.8 107.4 92.3 20.9

Raw Data


Summary Of Results

Difference in ESEManual vs AEC

(mR) %

Range 92-788 21-88

Average 304 52


Summary Data

Avg kVp Manual AEC mAs mAs ESE ESE mR %

Test # Measured kVp kVp Manual AEC Manual AEC Difference Difference

All

AVG 75.18 75.00 75.00 40.13 19.43 539.40 235.20 304.20 51.51

Max 78.35 76.00 76.00 64.00 33.65 947.29 360.75 787.62 88.00

Min 69.84 70.00 70.00 25.00 8.38 301.77 107.37 92.26 20.89

Film

AVG 74.76 75.10 75.10 36.80 19.39 467.53 236.11 231.42 47.58

Max 77.41 76.00 76.00 50.00 33.65 580.87 349.42 427.01 76.10

Min 69.84 75.00 75.00 25.00 10.48 301.77 134.10 92.26 20.89

CR

AVG 76.03 74.80 74.80 46.80 19.50 683.13 233.38 449.76 59.38

Max 78.35 76.00 76.00 64.00 33.58 947.29 360.75 787.62 88.00

Min 72.66 70.00 70.00 40.00 8.38 402.36 107.37 141.21 32.16


Summary Of ResultsDifference in ESEManual vs AEC

(mR) %

All 92-788 21-88Film 92-427 21-76

Ran

ge

CR 141-788 32-88All 304 52Film 231 48

Average CR 450 59


ESE Difference (Manual vs AEC)

48

5952

0.00

10.00

20.00

30.00

40.00

50.00

60.00

70.00

80.00

90.00

100.00

1 2 3 4 5 6 7 8 9 10Test #

% D

iffer

ence

Film CR Average


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. 23-24 cm Techniques


Reasons for Variance?

• AEC more efficient than manual techniques– For Same kVp settings, mAs was 2 to 8 times

less than manual counterpart


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)?


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


Lucite 2.4 mm 2.0 mm Lucite 2.4mm 2.0mm mR mR % Diff % Diff

Phantom Cu AEC Cu AEC Phantom Cu AEC Cu AEC 2.4 2 2.4 mm CU 2.0mm CU

Test # mAs mAs mAs ESE ESE ESE diff diff ESE ESE

1 8.38 14.40 8.10 107.37 169.12 90.66 -61.75 16.71 -58% 16%

2 13.30 21.70 12.00 198.32 288.25 160.40 -89.93 37.92 -45% 19%

3 15.50 22.50 12.50 239.29 301.62 164.47 -62.33 74.82 -26% 31%

4 26.73 20.90 11.90 261.15 199.75 106.21 61.40 154.94 24% 59%

5 28.83 47.80 22.50 243.65 387.05 184.23 -143.40 59.42 -59% 24%

6 14.48 10.90 6.81 199.44 149.66 92.33 49.78 107.11 25% 54%

7 12.05 12.90 6.60 134.10 130.76 68.00 3.34 66.10 2% 49%

8 33.58 50.50 24.80 360.75 458.53 228.40 -97.78 132.35 -27% 37%

Ave 19.10 25.20 13.15 218.01 260.59 136.84 -42.58 81.17 -20% 36%

Max 33.58 50.50 24.80 360.75 458.53 228.40 61.40 154.94 25% 59%

Min 8.38 10.90 6.60 107.37 130.76 68.00 -143.40 16.71 -59% 16%

ESE Difference Lucite vs Copper


Summary Of Results

Difference in AEC ESELucite vs Copper

(mR) %

2.4mm

-143 to 62 -59 to 25

Ran

ge

2.0mm

17 to 155 16 to 59

2.4mm

-43 -20

Average 2.0

mm81 36


ESE Difference Copper vs Lucite Phantom Materials

-80%

-60%

-40%

-20%

0%

20%

40%

60%

80%

1 2 3 4 5 6 7 8

Test #

% D

iffe

ren

ce% Diff 2.4 mm CU ESE % Diff 2.0mm CU ESE


Physicist Input

• Suggestions?• Phantom Materials?• Volunteers to Develop

AEC Protocol?

Pilot Study Comparing Patient ESE Manual vs. AEC Technique Factors.

Documents

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