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Quantification and correction of the scattered X-rays from a megavoltage photon beam to a linac-mounted kilovoltage imaging subsystem

OBJECTIVE: To quantify and correct megavoltage (MV) scattered X-rays (MV-scatter) on an image acquired using a linac-mounted kilovoltage (kV) imaging subsystem. METHODS AND MATERIALS: A linac-mounted flat-panel detector (FPD) was used to acquire an image containing MV-scatter by activating the FPD o...

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Autores principales: Iramina, Hiraku, Nakamura, Mitsuhiro, Miyabe, Yuki, Mukumoto, Nobutaka, Ono, Tomohiro, Hirashima, Hideaki, Mizowaki, Takashi
Formato: Online Artículo Texto
Lenguaje:English
Publicado: The British Institute of Radiology. 2020
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7731796/
https://www.ncbi.nlm.nih.gov/pubmed/33324865
http://dx.doi.org/10.1259/bjro.20190048
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author Iramina, Hiraku
Nakamura, Mitsuhiro
Miyabe, Yuki
Mukumoto, Nobutaka
Ono, Tomohiro
Hirashima, Hideaki
Mizowaki, Takashi
author_facet Iramina, Hiraku
Nakamura, Mitsuhiro
Miyabe, Yuki
Mukumoto, Nobutaka
Ono, Tomohiro
Hirashima, Hideaki
Mizowaki, Takashi
author_sort Iramina, Hiraku
collection PubMed
description OBJECTIVE: To quantify and correct megavoltage (MV) scattered X-rays (MV-scatter) on an image acquired using a linac-mounted kilovoltage (kV) imaging subsystem. METHODS AND MATERIALS: A linac-mounted flat-panel detector (FPD) was used to acquire an image containing MV-scatter by activating the FPD only during MV beam irradiation. 6-, 10-, and 15 MV with a flattening-filter (FF; 6X-FF, 10X-FF, 15X-FF), and 6- and 10 MV without an FF (6X-FFF, 10X-FFF) were used. The maps were acquired by changing one of the irradiation parameters while the others remained fixed. The mean pixel values of the MV-scatter were normalized to the 6X-FF reference condition (MV-scatter value). An MV-scatter database was constructed using these values. An MV-scatter correction experiment with one full arc image acquisition and two square field sizes (FSs) was conducted. Measurement- and estimation-based corrections were performed using the database. The image contrast was calculated at each angle. RESULTS: The MV-scatter increased with a larger FS and dose rate. The MV-scatter value factor varied substantially depending on the FPD position or collimator rotation. The median relative error ranges of the contrast for the image without, and with the measurement- and estimation-based correction were −10.9 to −2.9, and −1.5 to 4.8 and −7.4 to 2.6, respectively, for an FS of 10.0 × 10.0 cm(2). CONCLUSIONS: The MV-scatter was strongly dependent on the FS, dose rate, and FPD position. The MV-scatter correction improved the image contrast. ADVANCES IN KNOWLEDGE: The MV-scatters on the TrueBeam linac kV imaging subsystem were quantified with various MV beam parameters, and strongly depended on the fieldsize, dose rate, and flat panel detector position. The MV-scatter correction using the constructed database improved the image quality.
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spelling pubmed-77317962020-12-14 Quantification and correction of the scattered X-rays from a megavoltage photon beam to a linac-mounted kilovoltage imaging subsystem Iramina, Hiraku Nakamura, Mitsuhiro Miyabe, Yuki Mukumoto, Nobutaka Ono, Tomohiro Hirashima, Hideaki Mizowaki, Takashi BJR Open Original Research OBJECTIVE: To quantify and correct megavoltage (MV) scattered X-rays (MV-scatter) on an image acquired using a linac-mounted kilovoltage (kV) imaging subsystem. METHODS AND MATERIALS: A linac-mounted flat-panel detector (FPD) was used to acquire an image containing MV-scatter by activating the FPD only during MV beam irradiation. 6-, 10-, and 15 MV with a flattening-filter (FF; 6X-FF, 10X-FF, 15X-FF), and 6- and 10 MV without an FF (6X-FFF, 10X-FFF) were used. The maps were acquired by changing one of the irradiation parameters while the others remained fixed. The mean pixel values of the MV-scatter were normalized to the 6X-FF reference condition (MV-scatter value). An MV-scatter database was constructed using these values. An MV-scatter correction experiment with one full arc image acquisition and two square field sizes (FSs) was conducted. Measurement- and estimation-based corrections were performed using the database. The image contrast was calculated at each angle. RESULTS: The MV-scatter increased with a larger FS and dose rate. The MV-scatter value factor varied substantially depending on the FPD position or collimator rotation. The median relative error ranges of the contrast for the image without, and with the measurement- and estimation-based correction were −10.9 to −2.9, and −1.5 to 4.8 and −7.4 to 2.6, respectively, for an FS of 10.0 × 10.0 cm(2). CONCLUSIONS: The MV-scatter was strongly dependent on the FS, dose rate, and FPD position. The MV-scatter correction improved the image contrast. ADVANCES IN KNOWLEDGE: The MV-scatters on the TrueBeam linac kV imaging subsystem were quantified with various MV beam parameters, and strongly depended on the fieldsize, dose rate, and flat panel detector position. The MV-scatter correction using the constructed database improved the image quality. The British Institute of Radiology. 2020-12-11 /pmc/articles/PMC7731796/ /pubmed/33324865 http://dx.doi.org/10.1259/bjro.20190048 Text en © 2020 The Authors. Published by the British Institute of Radiology This is an open access article distributed under the terms of the Creative Commons Attribution 4.0 International License (https://creativecommons.org/licenses/by/4.0/) , which permits unrestricted use, distribution and reproduction in any medium, provided the original author and source are credited.
spellingShingle Original Research
Iramina, Hiraku
Nakamura, Mitsuhiro
Miyabe, Yuki
Mukumoto, Nobutaka
Ono, Tomohiro
Hirashima, Hideaki
Mizowaki, Takashi
Quantification and correction of the scattered X-rays from a megavoltage photon beam to a linac-mounted kilovoltage imaging subsystem
title Quantification and correction of the scattered X-rays from a megavoltage photon beam to a linac-mounted kilovoltage imaging subsystem
title_full Quantification and correction of the scattered X-rays from a megavoltage photon beam to a linac-mounted kilovoltage imaging subsystem
title_fullStr Quantification and correction of the scattered X-rays from a megavoltage photon beam to a linac-mounted kilovoltage imaging subsystem
title_full_unstemmed Quantification and correction of the scattered X-rays from a megavoltage photon beam to a linac-mounted kilovoltage imaging subsystem
title_short Quantification and correction of the scattered X-rays from a megavoltage photon beam to a linac-mounted kilovoltage imaging subsystem
title_sort quantification and correction of the scattered x-rays from a megavoltage photon beam to a linac-mounted kilovoltage imaging subsystem
topic Original Research
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7731796/
https://www.ncbi.nlm.nih.gov/pubmed/33324865
http://dx.doi.org/10.1259/bjro.20190048
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