PHOTOSTIMULABLE-PHOSPHOR PLATE (PSP)

RESPONSES IN COMPUTED RADIOGRAPHY AT

EXPOSURE FACTOR ASCENT RELATED TO TUBE

VOLTAGE ACCURACY & OUTPUT LINEARITY OF

X-RAY MACHINE

DWI ADHIANTO

24040112150010

MEDICAL PHYSICS TRANSFER PROGRAM

SCIENCE AND MATH FACULTY

DIPONEGORO UNIVERSITY

SEMARANG

2014

INTRODUCTION

Accuracy of control panel-radiation output

become one of aim for quality control in

radiology services.

General using of Computed Radiography in

Indonesia .

Linear response of imaging plate to x-ray

intensities

Tube voltage accuracy and linearity of output

from x-ray machine use photostimulable-

phosphor plate responses which is basic of

Computed Radiography technology

PROBLEM FORMULATION

AIM OF RESEARCH

Understanding influence of the gradual ascent

of exposure factor in x-ray machine to

photostimulablephosphor plate responses

related to tube voltage accuracy and linearity

of output x-ray machine.

RESEARCH PROFIT

Giving an alternative way for the Hospital that held

Computed Radiography System to perform

compliance test by using imaging plate responses.

COMPUTED RADIOGRAPHY

BASIC OF RESEARCH

COMPUTED RADIOGRAPHY RESPONSES

1. EXPOSURE INDEX

2. DEVIATION INDEX

3. IEC STANDARD 62494-1

4. MEAN GRAY VALUE

RESEARCH INSTRUMENTATION

&MATERIAL

• RADIODIAGNOSTIC MACHINE

• COMPUTED RADIOGRAPHY

(CARESTREAM)

• X-RAY ANALYZER PIRANHA

• ALLUMINIUM STEPWEDGE

RESEARCH METHODE

Compliance Test :

1. Tube Voltage Accuracy

2. Tube Current Linearity

3. X-Ray Reproducibility

ExaminationTable

X-ray Tube

Detector

SID

GETTING PRIMARY DATA

CR Positioning

CR Expose CR ReadingExposure indicator

Value entry

Analyzing digital image

ImageJ1.46r

X-rar Tube

STEPWEDGE

SID

Imaging Plate

Examination table

RESULT OF THE RESEARCH

COMPLIANCE TEST RESULT:

Tube Voltage Accuracy: Inaccuracy maximum is 1,4 % in 90 kVp

Tube Current Linearity:Maximum Difference in mGy/mAs at 0,3 %

X-Ray Reproducibility:Coefficient variation of voltage reproducibility is 0,01

& Exposure reproducibility is 0,01

Relation of linear ascent in tube voltage (kVp) with steady

tube current-exposure time (mAs) to Exposure Index

y = 1712.ln(x) - 5669.R² = 0.979

y = 1785.ln(x) - 5720.R² = 0.983

y = 1868.ln(x) - 5815.R² = 0.967

y = 1870.ln(x) - 5574.R² = 0.971

y = 1872.ln(x) - 5300.R² = 0.962

y = 1926.ln(x) - 5275R² = 0.959

0

500

1000

1500

2000

2500

3000

3500

40 50 60 70 80 90 100

Exp

osu

re In

dex

Tube Voltage (kVp)

0,5 mAs

1 mAs

2 mAs

4 mAs

8 mAs

16 mAs

y = 19.06x - 933.8R² = 0.952

y = 39.41x - 1949.R² = 0.962

y = 78.21x - 3820.R² = 0.954

y = 149.1x - 7341.R² = 0.940

y = 320.8x - 15791R² = 0.952

y = 633.6x - 31140R² = 0.959

0

5000

10000

15000

20000

25000

30000

40 50 60 70 80 90 100

IEC

Sta

nd

ard

Tube Voltage (kVp)

0,5 mAs

1 mAs

2 mAs

4 mAs

8 mAs

16 mAs

Relation of linear ascent in tube voltage (kVp) with steady

tube current-exposure time (mAs) to IEC Standard

Relation of linear ascent in tube voltage (kVp) with steady

tube current-exposure time (mAs) to Deviation Index

y = 18.19ln(x) - 78.09R² = 0.980

y = 18.02ln(x) - 74.29R² = 0.991

y = 18.02ln(x) - 71.19R² = 0.979

y = 18.42ln(x) - 70.04R² = 0.987

y = 18.38ln(x) - 66.67R² = 0.982

y = 18.15ln(x) - 62.74R² = 0.986

-10

-5

0

5

10

15

20

25

40 50 60 70 80 90 100

Dev

iati

on

ind

ex

Tube Voltage (kVp)

0,5 mAs

1 mAs

2 mAs

4 mAs

8 mAs

16 mAs

Relation of linear ascent in tube voltage (kVp) with steady

tube current-exposure time (mAs) to Mean Gray value

y = 909.5ln(x) - 2370.R² = 0.905

y = 672.0ln(x) - 1224.R² = 0.846

y = 442.2ln(x) - 103.3R² = 0.696

y = 625.2ln(x) - 794.4R² = 0.738

y = 461.0ln(x) + 8.540R² = 0.829y = 393.6ln(x) + 362.5

R² = 0.405

0

1000

2000

3000

40 50 60 70 80 90 100

Me

an G

ray

Val

ue

Tube Voltage (kVp)

0,5 mAs

1 mAs

2 mAs

4 mAs

8 mAs

16 mAs

Relation of linear ascent in tube current-exposure time (mAs) with steady

tube voltage (kVp) to Exposure Index

y = 344.3ln(x) + 1198.R² = 0.998

y = 387.3ln(x) + 1641.R² = 0.999

y = 381.0ln(x) + 1940.R² = 0.999

y = 376.6ln(x) + 2076R² = 0.999

y = 387.7ln(x) + 2269.R² = 0.999

0

1000

2000

3000

4000

0 5 10 15 20

Exp

osu

re In

dex

Current-Exposure Time (mAs)

50 kVp

60 kVp

70 kVp

80 kVp

90 kVp

Relation of linear ascent in tube current-exposure time (mAs) with steady

tube voltage (kVp) to IEC Standard

y = 141.5x - 11.36R² = 0.999

y = 400.6x - 25.48R² = 0.999

y = 726.5x + 23.91R² = 0.999

y = 1090.x - 157.5R² = 0.999

y = 1785.x - 49.45R² = 0.999

0

5000

10000

15000

20000

25000

30000

0 5 10 15 20

IEC

Sta

nd

ard

Current-Exposure Time (mAs)

50 kVp

60 kVp

70 kVp

80 kVp

90 kVp

Relation of linear ascent in tube current-exposure time (mAs) with steady

tube voltage (kVp) to Deviation Index

y = 4.330ln(x) - 4.352R² = 0.999

y = 4.460ln(x) - 0.099R² = 0.999

y = 4.279ln(x) + 2.939R² = 0.999

y = 4.422ln(x) + 4.342R² = 0.999

y = 4.387ln(x) + 6.588R² = 0.999

-10

-5

0

5

10

15

20

25

0 5 10 15 20

Dev

iati

on

Ind

ex

Current-Exposure Time (mAs)

50 kVp

60 kVp

70 kVp

80 kVp

90 kVp

Relation of linear ascent in tube current-exposure time (mAs) with steady

tube voltage (kVp) to Mean Gray Value

y = 215.4ln(x) + 1417.R² = 0.971

y = 153.9ln(x) + 1525.R² = 0.882y = 175.2ln(x) + 1562

R² = 0.988

y = 91.50ln(x) + 1730.R² = 0.860

y = 160.0ln(x) + 1846.R² = 0.959

0

500

1000

1500

2000

2500

0 2 4 6 8 10 12 14 16 18

Mea

n G

ray

Val

ue

Current-Exposure Time (mAs)

50 kVp

60 kVp

70 kVp

80 kVp

90 kVp

Coefficient of Linearity |X1 – X2| ≤ 0.1 (X1 + X2)

Result of Measuring of mAs linearity by Piranha analyzer

achieved maximum Coefficient of Linearity amount 0,0031

Result of Calculating IEC Standard/mAs achieved Coefficient

of Linearity amount 0,005-0,061

y = 0.051x - 0.000R² = 1

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

0 5 10 15 20

Eksp

osu

r (m

Gy)

Arus tabung-Waktu penyinaran (mAs)

CONCLUSION

• Exposure indicator in CR that used in this research is calibrated because it has linear responses to the radiation output compare to result of compliance test with Piranha Analyzer

• Linearity of mAs can be decided with a calibrated imaging plate

• Deciding a coefficient of mAs linearity can

be done with IEC Standard/mAs data.

CONCLUSION

• Determining of tube voltage accuracy with an

Exposure indicator can be done.

• Mean gray value is able to be an indicator of

mAs linearity because has a coefficient of

correlation more than 0,94.

SUGESTION

• Doing research to density of film print out in

same condition as the research.

• Doing research for the others CR vendor.

THANKS FOR THE ATTENTION