TY - JOUR
T1 - Determination of the electronic portal imaging device pixel-sensitivity-map for quality assurance applications. Part 2
T2 - Photon beam dependence
AU - Barnes, Michael Paul
AU - Sun, Baozhou
AU - Oborn, Brad Michael
AU - Lamichhane, Bishnu
AU - Szwec, Stuart
AU - Schmidt, Matthew
AU - Cai, Bin
AU - Menk, Frederick
AU - Greer, Peter
N1 - Publisher Copyright:
© 2022 The Authors. Journal of Applied Clinical Medical Physics published by Wiley Periodicals, LLC on behalf of The American Association of Physicists in Medicine.
PY - 2022/6
Y1 - 2022/6
N2 - Purpose: The EPID PSM is a useful EPID calibration method for QA applications. The dependence of the EPID PSM on the photon beam used to acquire it has been investigated in this study for the four available PSM methods. The aim is to inform upon the viability of applying a single PSM for all available photon beams to simplify PSM implementation and maintenance. Methods: Four methods of PSM determination were each measured once in a single session on a single TrueBeam ® STx linac using 6 MV, 10 MV, 6 MV Flattening-Filter-Free (FFF), and 10 MV FFF photon beams. The resultant PSM was assessed for both intra- and inter-method beam dependence via comparison between PSM of the same method compared to the 6 MV PSM and via comparison between PSM of the same beam with the corresponding Monte Carlo PSM. Comparisons were performed via 2D percentage deviation plots with associated histograms, 1D crossplane profiles, and via mean, median, and standard deviation percentage deviation statistics. Generated beam-response was compared qualitatively via 1D crossplane profile comparison and quantitatively via symmetry assessment with comparison to the IC profiler device. Results: The Varian method provided the most consistent PSM with varying photon beam, with median percent deviation from the 6 MV PSM within 0.14% for all other beams. Qualitatively, each method provided similar beam-response profiles. The measured beam-response symmetry agreed to within 0.2% between the Calvary Mater Newcastle (CMN) method and IC profiler, but agreement reduced to within 0.9% and 2.2% for the Varian and WashU methods. PSM percent deviation with Monte Carlo PSM was within 0.75% for all methods and beams. Conclusion: Results suggest that the PSM may be independent of photon beam to clinically relevant levels. The Varian method of PSM determination introduces the least beam dependence into the measured PSM.
AB - Purpose: The EPID PSM is a useful EPID calibration method for QA applications. The dependence of the EPID PSM on the photon beam used to acquire it has been investigated in this study for the four available PSM methods. The aim is to inform upon the viability of applying a single PSM for all available photon beams to simplify PSM implementation and maintenance. Methods: Four methods of PSM determination were each measured once in a single session on a single TrueBeam ® STx linac using 6 MV, 10 MV, 6 MV Flattening-Filter-Free (FFF), and 10 MV FFF photon beams. The resultant PSM was assessed for both intra- and inter-method beam dependence via comparison between PSM of the same method compared to the 6 MV PSM and via comparison between PSM of the same beam with the corresponding Monte Carlo PSM. Comparisons were performed via 2D percentage deviation plots with associated histograms, 1D crossplane profiles, and via mean, median, and standard deviation percentage deviation statistics. Generated beam-response was compared qualitatively via 1D crossplane profile comparison and quantitatively via symmetry assessment with comparison to the IC profiler device. Results: The Varian method provided the most consistent PSM with varying photon beam, with median percent deviation from the 6 MV PSM within 0.14% for all other beams. Qualitatively, each method provided similar beam-response profiles. The measured beam-response symmetry agreed to within 0.2% between the Calvary Mater Newcastle (CMN) method and IC profiler, but agreement reduced to within 0.9% and 2.2% for the Varian and WashU methods. PSM percent deviation with Monte Carlo PSM was within 0.75% for all methods and beams. Conclusion: Results suggest that the PSM may be independent of photon beam to clinically relevant levels. The Varian method of PSM determination introduces the least beam dependence into the measured PSM.
KW - EPID dosimetry
KW - pixel-sensitivity-map
KW - quality assurance
UR - http://www.scopus.com/inward/record.url?scp=85128989084&partnerID=8YFLogxK
U2 - 10.1002/acm2.13602
DO - 10.1002/acm2.13602
M3 - Article
C2 - 35429117
AN - SCOPUS:85128989084
SN - 1526-9914
VL - 23
JO - Journal of applied clinical medical physics
JF - Journal of applied clinical medical physics
IS - 6
M1 - e13602
ER -