Current best estimates of beam quality correction factors for reference dosimetry of clinical proton beams
(2022) In Physics in Medicine and Biology 67(19).- Abstract
Objective. To review the currently available data on beam quality correction factors, kQ, for ionization chambers in clinical proton beams and derive their current best estimates for the updated recommendations of the IAEA TRS-398 Code of Practice. Approach. The reviewed data come from 20 publications from which kQ values can be derived either directly from calorimeter measurements, indirectly from comparison with other chambers or from Monte Carlo calculated overall chamber factors, fQ. For cylindrical ionization chambers, a distinction is made between data obtained in the centre of a spread-out Bragg peak and those obtained in the plateau region of single-energy fields. For the latter, the effect of depth dose gradients has to be... (More)
Objective. To review the currently available data on beam quality correction factors, kQ, for ionization chambers in clinical proton beams and derive their current best estimates for the updated recommendations of the IAEA TRS-398 Code of Practice. Approach. The reviewed data come from 20 publications from which kQ values can be derived either directly from calorimeter measurements, indirectly from comparison with other chambers or from Monte Carlo calculated overall chamber factors, fQ. For cylindrical ionization chambers, a distinction is made between data obtained in the centre of a spread-out Bragg peak and those obtained in the plateau region of single-energy fields. For the latter, the effect of depth dose gradients has to be considered. To this end an empirical model for previously published displacement correction factors for single-layer scanned beams was established, while for unmodulated scattered beams experimental data were used. From all the data, chamber factors, fQ, and chamber perturbation correction factors, pQ, were then derived and analysed. Main results. The analysis showed that except for the beam quality dependence of the water-to-air mass stopping power ratio and, for cylindrical ionization chambers in unmodulated beams, of the displacement correction factor, there is no remaining beam quality dependence of the chamber perturbation correction factors pQ. Based on this approach, average values of the beam quality independent part of the perturbation factors were derived to calculate kQ values consistent with the data in the literature. Significance. The resulting data from this analysis are current best estimates of kQ values for modulated scattered beams and single-layer scanned beams used in proton therapy. Based on this, a single set of harmonized values is derived to be recommended in the update of IAEA TRS-398.
(Less)
- author
- Palmans, Hugo ; Lourenço, Ana ; Medin, Joakim LU ; Vatnitsky, Stanislav and Andreo, Pedro
- organization
- publishing date
- 2022-10-07
- type
- Contribution to journal
- publication status
- published
- subject
- keywords
- beam quality correction factor, IAEA TRS-398 update, ionization chamber, proton beam, reference dosimetry
- in
- Physics in Medicine and Biology
- volume
- 67
- issue
- 19
- article number
- 195012
- publisher
- IOP Publishing
- external identifiers
-
- pmid:36096096
- scopus:85139659651
- ISSN
- 0031-9155
- DOI
- 10.1088/1361-6560/ac9172
- language
- English
- LU publication?
- yes
- id
- 3d727230-bef2-472c-b6e7-b2e250d9a393
- date added to LUP
- 2022-12-13 16:25:19
- date last changed
- 2024-04-18 17:15:56
@article{3d727230-bef2-472c-b6e7-b2e250d9a393,
abstract = {{<p>Objective. To review the currently available data on beam quality correction factors, kQ, for ionization chambers in clinical proton beams and derive their current best estimates for the updated recommendations of the IAEA TRS-398 Code of Practice. Approach. The reviewed data come from 20 publications from which kQ values can be derived either directly from calorimeter measurements, indirectly from comparison with other chambers or from Monte Carlo calculated overall chamber factors, fQ. For cylindrical ionization chambers, a distinction is made between data obtained in the centre of a spread-out Bragg peak and those obtained in the plateau region of single-energy fields. For the latter, the effect of depth dose gradients has to be considered. To this end an empirical model for previously published displacement correction factors for single-layer scanned beams was established, while for unmodulated scattered beams experimental data were used. From all the data, chamber factors, fQ, and chamber perturbation correction factors, pQ, were then derived and analysed. Main results. The analysis showed that except for the beam quality dependence of the water-to-air mass stopping power ratio and, for cylindrical ionization chambers in unmodulated beams, of the displacement correction factor, there is no remaining beam quality dependence of the chamber perturbation correction factors pQ. Based on this approach, average values of the beam quality independent part of the perturbation factors were derived to calculate kQ values consistent with the data in the literature. Significance. The resulting data from this analysis are current best estimates of kQ values for modulated scattered beams and single-layer scanned beams used in proton therapy. Based on this, a single set of harmonized values is derived to be recommended in the update of IAEA TRS-398.</p>}},
author = {{Palmans, Hugo and Lourenço, Ana and Medin, Joakim and Vatnitsky, Stanislav and Andreo, Pedro}},
issn = {{0031-9155}},
keywords = {{beam quality correction factor; IAEA TRS-398 update; ionization chamber; proton beam; reference dosimetry}},
language = {{eng}},
month = {{10}},
number = {{19}},
publisher = {{IOP Publishing}},
series = {{Physics in Medicine and Biology}},
title = {{Current best estimates of beam quality correction factors for reference dosimetry of clinical proton beams}},
url = {{http://dx.doi.org/10.1088/1361-6560/ac9172}},
doi = {{10.1088/1361-6560/ac9172}},
volume = {{67}},
year = {{2022}},
}