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Title: SU-E-J-69: Iterative Deconvolution of the Initial Photon Fluence for EPID Dosimetry: A Monte Carlo Based Study

Abstract

Purpose: Developing a fast and accurate calculation model to reconstruct the applied photon fluence from an external photon radiation therapy treatment based on an image recorded by an electronic portal image device (EPID). Methods: To reconstruct the initial photon fluence the 2D EPID image was corrected for scatter from the patient/phantom and EPID to generate the transmitted primary photon fluence. This was done by an iterative deconvolution using precalculated point spread functions (PSF). The transmitted primary photon fluence was then backprojected through the patient/phantom geometry considering linear attenuation to receive the initial photon fluence applied for the treatment.The calculation model was verified using Monte Carlo simulations performed with the EGSnrc code system. EPID images were produced by calculating the dose deposition in the EPID from a 6 MV photon beam irradiating a water phantom with air and bone inhomogeneities and the ICRP anthropomorphic voxel phantom. Results: The initial photon fluence was reconstructed using a single PSF and position dependent PSFs which depend on the radiological thickness of the irradiated object. Appling position dependent point spread functions the mean uncertainty of the reconstructed initial photon fluence could be reduced from 1.13 % to 0.13 %. Conclusion: This study presents a calculationmore » model for fluence reconstruction from EPID images. The{sup Result} show a clear advantage when position dependent PSF are used for the iterative reconstruction. The basic work of a reconstruction method was established and further evaluations must be made in an experimental study.« less

Authors:
; ;  [1];  [1]
  1. Technische Hochschule Mittelhessen - University of Applied Sciences, Giessen (Germany)
Publication Date:
OSTI Identifier:
22494089
Resource Type:
Journal Article
Journal Name:
Medical Physics
Additional Journal Information:
Journal Volume: 42; Journal Issue: 6; Other Information: (c) 2015 American Association of Physicists in Medicine; Country of input: International Atomic Energy Agency (IAEA); Journal ID: ISSN 0094-2405
Country of Publication:
United States
Language:
English
Subject:
60 APPLIED LIFE SCIENCES; ATTENUATION; COMPUTERIZED SIMULATION; DOSIMETRY; EQUIPMENT; EVALUATION; ICRP; IMAGES; IRRADIATION; ITERATIVE METHODS; MONTE CARLO METHOD; PATIENTS; PHANTOMS; PHOTON BEAMS; RADIATION DOSES; RADIOTHERAPY; SKELETON; THICKNESS

Citation Formats

Czarnecki, D, Voigts-Rhetz, P von, Shishechian, D Uchimura, Zink, K, and Germany and Department of Radiotherapy and Radiooncology, University Medical Center Giessen-Marburg, Marburg. SU-E-J-69: Iterative Deconvolution of the Initial Photon Fluence for EPID Dosimetry: A Monte Carlo Based Study. United States: N. p., 2015. Web. doi:10.1118/1.4924156.
Czarnecki, D, Voigts-Rhetz, P von, Shishechian, D Uchimura, Zink, K, & Germany and Department of Radiotherapy and Radiooncology, University Medical Center Giessen-Marburg, Marburg. SU-E-J-69: Iterative Deconvolution of the Initial Photon Fluence for EPID Dosimetry: A Monte Carlo Based Study. United States. https://doi.org/10.1118/1.4924156
Czarnecki, D, Voigts-Rhetz, P von, Shishechian, D Uchimura, Zink, K, and Germany and Department of Radiotherapy and Radiooncology, University Medical Center Giessen-Marburg, Marburg. 2015. "SU-E-J-69: Iterative Deconvolution of the Initial Photon Fluence for EPID Dosimetry: A Monte Carlo Based Study". United States. https://doi.org/10.1118/1.4924156.
@article{osti_22494089,
title = {SU-E-J-69: Iterative Deconvolution of the Initial Photon Fluence for EPID Dosimetry: A Monte Carlo Based Study},
author = {Czarnecki, D and Voigts-Rhetz, P von and Shishechian, D Uchimura and Zink, K and Germany and Department of Radiotherapy and Radiooncology, University Medical Center Giessen-Marburg, Marburg},
abstractNote = {Purpose: Developing a fast and accurate calculation model to reconstruct the applied photon fluence from an external photon radiation therapy treatment based on an image recorded by an electronic portal image device (EPID). Methods: To reconstruct the initial photon fluence the 2D EPID image was corrected for scatter from the patient/phantom and EPID to generate the transmitted primary photon fluence. This was done by an iterative deconvolution using precalculated point spread functions (PSF). The transmitted primary photon fluence was then backprojected through the patient/phantom geometry considering linear attenuation to receive the initial photon fluence applied for the treatment.The calculation model was verified using Monte Carlo simulations performed with the EGSnrc code system. EPID images were produced by calculating the dose deposition in the EPID from a 6 MV photon beam irradiating a water phantom with air and bone inhomogeneities and the ICRP anthropomorphic voxel phantom. Results: The initial photon fluence was reconstructed using a single PSF and position dependent PSFs which depend on the radiological thickness of the irradiated object. Appling position dependent point spread functions the mean uncertainty of the reconstructed initial photon fluence could be reduced from 1.13 % to 0.13 %. Conclusion: This study presents a calculation model for fluence reconstruction from EPID images. The{sup Result} show a clear advantage when position dependent PSF are used for the iterative reconstruction. The basic work of a reconstruction method was established and further evaluations must be made in an experimental study.},
doi = {10.1118/1.4924156},
url = {https://www.osti.gov/biblio/22494089}, journal = {Medical Physics},
issn = {0094-2405},
number = 6,
volume = 42,
place = {United States},
year = {Mon Jun 15 00:00:00 EDT 2015},
month = {Mon Jun 15 00:00:00 EDT 2015}
}