1. Qing Liang, PhD Medical Physicist Mercy Health System, Janesville, WI
Dose Measurement
Qing Liang, PhD
Medical Physicist
Mercy Health System, Janesville, WI

2. Learning Objectives Learn about ionization calibration chain
Understand TG51 on photon beam and electron beam dosimetry
Overview of TRS398

3. References AAPM TG 51: Med Phys 26(9), 1999
AAPM TG 51 Addendum 41(4),2014
IAEA TRS 398
Khan, The Physics of Radiation Therapy
AAPM virtual library (website)

4. Part 1: Calibration Traceability
(ionization chamber)

5. Calibration Chain
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6. What is a PSDL?
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7. Primary Dosimetry Standard
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8. Secondary Standard Dosimetry Lab
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9. NIST National Institute of Standard and Technology
Dose measured by calorimeter, 60Co source
NIST calibrated chamber
:Absorbed dose in water rate (Gy/s)
I: ionization current (C/s)

10. ADCL
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11. Clinical calibration factor
NIST
ADCL
ADCL
ADCL
Clinic
Clinic
Clinic
Clinic
Clinic
Clinic

12. Part 2: AAPM TG51

13. AAPM TG51

14. AAPM TG51

15. TG51 Overview: photon
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16. TG51 Overview: electron
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17. TG51 Overview
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18. TG51 Overview
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19. TG51 Overview
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20. TG51 Phantom
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21. TG51 Chamber
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22. TG51 Effective point of Measurement
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23. TG51 Effective point of Measurement
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24. TG51 Chamber Reading Pion: recombination correction factor
Two voltage method (<1.05)

25. TG51 Chamber Reading PTP: temperature pressure correction
Correct for density compare to standard environmental condition: 22oC, kPa (760 mm Hg)

26. TG51 Chamber Reading Pelec: electrometer calibration factor
Provided by ADCL
Unit: C/C or C/rdg
If calibrated with chamber, Pelec=1
If calibrated separately, Pelec applied

27. TG51 Chamber Reading Ppol: polarity correction factor
Depends on chamber design, cable position and beam quality ( )

28. TG51 Beam Quality (P)
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29. TG51 Beam Quality (P)
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30. TG51 Beam Quality (P)
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31. TG51 Beam Quality (P) OR
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32. TG51 Beam Quality (P)
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33. TG51 Photon Dosimetry
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34. TG51 Photon Dosimetry
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35. TG51 Photon Summery
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36. TG51 Worksheet (P)

37. TG51 Beam Quality (E)
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38. TG51 Beam Quality (E)
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39. TG51 Beam Quality (E)
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40. TG51 Beam Quality (E)
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41. TG51 Beam Quality (E)
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42. TG51 Beam Quality (E)
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43. TG51 Beam Quality (E)
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44. TG51 Beam Quality (E)
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45. TG51 Beam Quality (E)
Kecal
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46. TG51 Electron Dosimetry
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47. TG51 Beam Quality (E)
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48. TG51 Electron Dosimetry
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49. TG51 Electron Dosimetry
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50. TG51 Electron Dosimetry
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51. TG51 Electron Summery
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52. TG51 Worksheet (E, cyl)

53. TG51 Worksheet (E, pp)

54. TG51 Summery
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55. TG51 Addendum

56. TG51 Addendum Covers
No lead foil to be used anymore (use equation)

57. Part 3: IAEA TRS 398

58. IAEA TRS 398

59. TRS 398 vs. TG 51
Basic equations are the same between TRS398 and TG51, expect notations
Main difference is the beam quality parameter kQ: TPR20,10 in TRS 398, vs. %dd(10)x in TG51

60. TRS 398 Setup: SAD Source to chamber distance: 100 cm
Field size: 10x10 cm2
Depth: 20 cm, 10 cm

61. Thank you!