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Title: Using fluence separation to account for energy spectra dependence in computing dosimetric a-Si EPID images for IMRT fields

Abstract

This study develops a method to improve the dosimetric accuracy of computed images for an amorphous silicon flat-panel imager. Radially dependent kernels derived from Monte Carlo simulations are convolved with the treatment-planning system's energy fluence. Multileaf collimator (MLC) beam hardening is accounted for by having separate kernels for open and blocked portions of MLC fields. Field-size-dependent output factors are used to account for the field-size dependence of scatter within the imager. Gamma analysis was used to evaluate open and sliding window test fields and intensity modulated patient fields. For each tested field, at least 99.6% of the points had {gamma}<1 with a 3%, 3-mm criteria. With a 2%, 2-mm criteria, between 81% and 100% of points had {gamma}<1. Patient intensity modulated test fields had 94%-100% of the points with {gamma}<1 with a 2%, 2-mm criteria for all six fields tested. This study demonstrates that including the dependencies of kernel and fluence on radius and beam hardening in the convolution improves its accuracy compared with the use of radial and beam-hardening independent kernels; it also demonstrates that the resultant accuracy of the convolution method is sufficient for pretreatment, intensity modulated patient field verification.

Authors:
; ;  [1]
  1. Department of Radiation Oncology, Medical College of Virginia Hospitals, Virginia Commonwealth University, Richmond, Virginia 23298 (United States)
Publication Date:
OSTI Identifier:
20853815
Resource Type:
Journal Article
Resource Relation:
Journal Name: Medical Physics; Journal Volume: 33; Journal Issue: 12; Other Information: DOI: 10.1118/1.2369468; (c) 2006 American Association of Physicists in Medicine; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
62 RADIOLOGY AND NUCLEAR MEDICINE; ACCURACY; COLLIMATORS; COMPUTERIZED SIMULATION; DOSIMETRY; ENERGY SPECTRA; IMAGES; KERNELS; MONTE CARLO METHOD; PATIENTS; RADIOTHERAPY; SILICON

Citation Formats

Li Weidong, Siebers, Jeffrey V., and Moore, Joseph A. Using fluence separation to account for energy spectra dependence in computing dosimetric a-Si EPID images for IMRT fields. United States: N. p., 2006. Web. doi:10.1118/1.2369468.
Li Weidong, Siebers, Jeffrey V., & Moore, Joseph A. Using fluence separation to account for energy spectra dependence in computing dosimetric a-Si EPID images for IMRT fields. United States. doi:10.1118/1.2369468.
Li Weidong, Siebers, Jeffrey V., and Moore, Joseph A. Fri . "Using fluence separation to account for energy spectra dependence in computing dosimetric a-Si EPID images for IMRT fields". United States. doi:10.1118/1.2369468.
@article{osti_20853815,
title = {Using fluence separation to account for energy spectra dependence in computing dosimetric a-Si EPID images for IMRT fields},
author = {Li Weidong and Siebers, Jeffrey V. and Moore, Joseph A.},
abstractNote = {This study develops a method to improve the dosimetric accuracy of computed images for an amorphous silicon flat-panel imager. Radially dependent kernels derived from Monte Carlo simulations are convolved with the treatment-planning system's energy fluence. Multileaf collimator (MLC) beam hardening is accounted for by having separate kernels for open and blocked portions of MLC fields. Field-size-dependent output factors are used to account for the field-size dependence of scatter within the imager. Gamma analysis was used to evaluate open and sliding window test fields and intensity modulated patient fields. For each tested field, at least 99.6% of the points had {gamma}<1 with a 3%, 3-mm criteria. With a 2%, 2-mm criteria, between 81% and 100% of points had {gamma}<1. Patient intensity modulated test fields had 94%-100% of the points with {gamma}<1 with a 2%, 2-mm criteria for all six fields tested. This study demonstrates that including the dependencies of kernel and fluence on radius and beam hardening in the convolution improves its accuracy compared with the use of radial and beam-hardening independent kernels; it also demonstrates that the resultant accuracy of the convolution method is sufficient for pretreatment, intensity modulated patient field verification.},
doi = {10.1118/1.2369468},
journal = {Medical Physics},
number = 12,
volume = 33,
place = {United States},
year = {Fri Dec 15 00:00:00 EST 2006},
month = {Fri Dec 15 00:00:00 EST 2006}
}