Comparison of IPSM 1990 photon dosimetry code of practice with IAEA TRS-398 and AAPM TG-51.

Silvia Vargas Castrillón,Francisco Cutanda Henríquez

doi:10.1120/jacmp.v10i1.2810

Silvia Vargas Castrillón, Francisco Cutanda Henríquez

Open Access

https://doi.org/10.1120/jacmp.v10i1.2810

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Abstract

Several codes of practice for photon dosimetry are currently used around the world, supported by different organizations. A comparison of IPSM 1990 with both IAEA TRS‐398 and AAPM TG‐51 has been performed. All three protocols are based on the calibration of ionization chambers in terms of standards of absorbed dose to water, as it is the case with other modern codes of practice. This comparison has been carried out for photon beams of nominal energies: 4 MV, 6 MV, 8 MV, 10 MV and 18 MV.An NE 2571 graphite ionization chamber was used in this study, cross‐calibrated against an NE 2611A Secondary Standard, calibrated in the National Physical Laboratory (NPL). Absolute dose in reference conditions was obtained using each of these three protocols including: beam quality indices, beam quality conversion factors both theoretical and NPL experimental ones, correction factors for influence quantities and absolute dose measurements. Each protocol recommendations have been strictly followed. Uncertainties have been obtained according to the ISO Guide to the Expression of Uncertainty in Measurement. Absorbed dose obtained according to all three protocols agree within experimental uncertainty. The largest difference between absolute dose results for two protocols is obtained for the highest energy: 0.7% between IPSM 1990 and IAEA TRS‐398 using theoretical beam quality conversion factors.PACS number: 87.55.tm

Highlights

IPSM (Institute of Physical Sciences in Medicine) 1990,(1) AAPM (American Association of Physicist in Medicine) Task Group 51,(2) and the IAEA (International Atomic Energy Agency) Technical Reports Series 398(3) codes of practice are based on the calibration of ionization chambers in terms of absorbed dose to water
The fit given in IAEA TRS-398 for TPR20,10 derived from PDD20,10 measurement has a maximum difference with regard to measured data of 0.6% for beam qualities below 50 MV
IPSM 1990 photon dosimetry code of practice has been compared with AAPM TG-51 and IAEA TRS-398, and the similarities and differences between IPSM 1990 and AAPM TG-51/IAEA TRS-398 have been discussed

Summary

Introduction

IPSM (Institute of Physical Sciences in Medicine) 1990,(1) AAPM (American Association of Physicist in Medicine) Task Group 51,(2) and the IAEA (International Atomic Energy Agency) Technical Reports Series 398(3) codes of practice are based on the calibration of ionization chambers in terms of absorbed dose to water. This approach is not limited to these codes of practice but is a worldwide trend which includes: German DIN 1997,(4) Japanese Association of Radiological Physics,(5) and the Swiss Society of Radiobiology and Medical Physics.[6] DIN in Germany[4,7] and IPSM in the United Kingdom[1,8] were pioneers in the use of standards of absorbed dose to water in their dosimetry protocols. IAEA TRS-398 provides the most general and flexible framework for calibration, allowing four very detailed possibilities that include the use of experimental or theoretical beam quality conversion factors (see Section 4.1, IAEA TRS-398)

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