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Title: The Dosimetric Effect of Zipper Artifacts on TomoTherapy Adaptive Dose Calculation-A Phantom Study

Abstract

Tomotherapy adaptive dose calculation offers the ability to verify and adjust the therapeutic plan during the treatment. Using tomotherapy adaptive dose calculation, the planned fluence pattern can be used to recalculate the dose distribution on pretreatment megavoltage computed tomography (MVCT) images. Zipper artifacts, which appear as increased density in the central region of MVCT images, may affect the accuracy of adaptive dose recalculation. The purpose of this study was to evaluate the dosimetric effects of zipper artifacts on tomotherapy adaptive dose calculation. MVCT images of a cylindrical water phantom of 22-cm diameter were acquired on a tomotherapy system. The zipper artifacts were enclosed by a cylindrical planning target volume (PTV) contoured on these images. For comparison, artifact-free images were created by replacing the computed tomography (CT) numbers of zipper artifacts with the mean CT number of water. Treatment plans were generated by giving a uniform dose of 2 Gy to the PTV based on these modified images; it was then applied to the images that have the zipper artifacts. The impacts of different pitch ratios on the artifacts were assessed. The dose distribution differences between the 2 sets of images were compared. The absorbed dose that covered 95% volume ofmore » PTV and maximum dose, minimum dose, and mean dose of the PTV were also calculated and compared. The water phantom was scanned on the tomotherapy system twice per week for 12 consecutive weeks. The mean CT number of zipper artifacts (101 HU) was three times higher than that of water (34 HU). The CT number value and location of zipper artifacts were not affected by the pitch ratio. Gamma analysis was performed between the original and recalculated dose distributions. The discrepancies between the isodose distributions calculated by two sets of images were within 1%/1-mm tolerance. The dosimetric impact from zipper artifacts was found insignificant such that the recalculated dose was underestimated by less than 0.5%.« less

Authors:
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Publication Date:
OSTI Identifier:
21590482
Resource Type:
Journal Article
Journal Name:
Medical Dosimetry
Additional Journal Information:
Journal Volume: 36; Journal Issue: 3; Other Information: DOI: 10.1016/j.meddos.2010.06.002; PII: S0958-3947(10)00112-3; Copyright (c) 2011 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved.; Country of input: International Atomic Energy Agency (IAEA); Journal ID: ISSN 0958-3947
Country of Publication:
United States
Language:
English
Subject:
61 RADIATION PROTECTION AND DOSIMETRY; ACCURACY; COMPUTERIZED TOMOGRAPHY; CT-GUIDED RADIOTHERAPY; DOSIMETRY; IMAGES; PHANTOMS; RADIATION DOSE DISTRIBUTIONS; RADIATION DOSES; DIAGNOSTIC TECHNIQUES; DOSES; MEDICINE; MOCKUP; NUCLEAR MEDICINE; RADIOLOGY; RADIOTHERAPY; STRUCTURAL MODELS; THERAPY; TOMOGRAPHY

Citation Formats

Geng Hui, E-mail: genghui_hk@yahoo.com.hk, Yu, Siu-Ki, Lam, Wai-Wang, Wong, Wing-Kei Rebecca, Ho, Yick-Wing, and Liu, Sau-Fan. The Dosimetric Effect of Zipper Artifacts on TomoTherapy Adaptive Dose Calculation-A Phantom Study. United States: N. p., 2011. Web. doi:10.1016/j.meddos.2010.06.002.
Geng Hui, E-mail: genghui_hk@yahoo.com.hk, Yu, Siu-Ki, Lam, Wai-Wang, Wong, Wing-Kei Rebecca, Ho, Yick-Wing, & Liu, Sau-Fan. The Dosimetric Effect of Zipper Artifacts on TomoTherapy Adaptive Dose Calculation-A Phantom Study. United States. doi:10.1016/j.meddos.2010.06.002.
Geng Hui, E-mail: genghui_hk@yahoo.com.hk, Yu, Siu-Ki, Lam, Wai-Wang, Wong, Wing-Kei Rebecca, Ho, Yick-Wing, and Liu, Sau-Fan. Sat . "The Dosimetric Effect of Zipper Artifacts on TomoTherapy Adaptive Dose Calculation-A Phantom Study". United States. doi:10.1016/j.meddos.2010.06.002.
@article{osti_21590482,
title = {The Dosimetric Effect of Zipper Artifacts on TomoTherapy Adaptive Dose Calculation-A Phantom Study},
author = {Geng Hui, E-mail: genghui_hk@yahoo.com.hk and Yu, Siu-Ki and Lam, Wai-Wang and Wong, Wing-Kei Rebecca and Ho, Yick-Wing and Liu, Sau-Fan},
abstractNote = {Tomotherapy adaptive dose calculation offers the ability to verify and adjust the therapeutic plan during the treatment. Using tomotherapy adaptive dose calculation, the planned fluence pattern can be used to recalculate the dose distribution on pretreatment megavoltage computed tomography (MVCT) images. Zipper artifacts, which appear as increased density in the central region of MVCT images, may affect the accuracy of adaptive dose recalculation. The purpose of this study was to evaluate the dosimetric effects of zipper artifacts on tomotherapy adaptive dose calculation. MVCT images of a cylindrical water phantom of 22-cm diameter were acquired on a tomotherapy system. The zipper artifacts were enclosed by a cylindrical planning target volume (PTV) contoured on these images. For comparison, artifact-free images were created by replacing the computed tomography (CT) numbers of zipper artifacts with the mean CT number of water. Treatment plans were generated by giving a uniform dose of 2 Gy to the PTV based on these modified images; it was then applied to the images that have the zipper artifacts. The impacts of different pitch ratios on the artifacts were assessed. The dose distribution differences between the 2 sets of images were compared. The absorbed dose that covered 95% volume of PTV and maximum dose, minimum dose, and mean dose of the PTV were also calculated and compared. The water phantom was scanned on the tomotherapy system twice per week for 12 consecutive weeks. The mean CT number of zipper artifacts (101 HU) was three times higher than that of water (34 HU). The CT number value and location of zipper artifacts were not affected by the pitch ratio. Gamma analysis was performed between the original and recalculated dose distributions. The discrepancies between the isodose distributions calculated by two sets of images were within 1%/1-mm tolerance. The dosimetric impact from zipper artifacts was found insignificant such that the recalculated dose was underestimated by less than 0.5%.},
doi = {10.1016/j.meddos.2010.06.002},
journal = {Medical Dosimetry},
issn = {0958-3947},
number = 3,
volume = 36,
place = {United States},
year = {2011},
month = {10}
}