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Quality Assurance of Beam Accuracy for Leksell Gamma Unit

For the acceptance test and annual quality assurance of the Leksell Gamma Unit, measurement of the beam accuracy, defined as a distance between mechanical and radiological isocenters, poses a challenge to medical physicists. The specification for the beam accuracy is within 0.5 mm for the 4‐mm colli...

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Autores principales: Yu, Cheng, Petrovich, Zbigniew, Luxton, Gary
Formato: Online Artículo Texto
Lenguaje:English
Publicado: John Wiley and Sons Inc. 2000
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5726164/
https://www.ncbi.nlm.nih.gov/pubmed/11674816
http://dx.doi.org/10.1120/jacmp.v1i1.2652
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author Yu, Cheng
Petrovich, Zbigniew
Luxton, Gary
author_facet Yu, Cheng
Petrovich, Zbigniew
Luxton, Gary
author_sort Yu, Cheng
collection PubMed
description For the acceptance test and annual quality assurance of the Leksell Gamma Unit, measurement of the beam accuracy, defined as a distance between mechanical and radiological isocenters, poses a challenge to medical physicists. The specification for the beam accuracy is within 0.5 mm for the 4‐mm collimator helmet. In this report, we introduce a simple technique to analyze the beam accuracy by using a conventional film densitometer plus mathematical modeling. A small piece of film was placed inside the film cassette containing a sharp needle. The needle is located such that its tip is exactly positioned at the mechanical isocenter. Before exposure, the film was pierced by the needle. Density profile was measured by using a densitometer with a spatial resolution of 0.8 mm. The profile was then fitted to a model of the two Gaussian functions. One is for the radiation field profile, the other for a dip caused by the narrow hole. The difference between the centers of the two Gaussian functions defines the deviation of the beam accuracy from the mechanical center of the unit. The deviations for x, y, and z directions from one of our annual measurements are 0.032, 0.054, and 0.195 mm, respectively. The combined deviation is 0.20 mm, which is well within the specification and in excellent agreement with the results from the manufacture's laser measurement. This technique provides a simple, accurate and practical tool for measurement of the beam accuracy in the acceptance test and annual quality assurance of the Leksell Gamma Unit. PACS number(s): 87.66.–a, 87.53.–j
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spelling pubmed-57261642018-04-02 Quality Assurance of Beam Accuracy for Leksell Gamma Unit Yu, Cheng Petrovich, Zbigniew Luxton, Gary J Appl Clin Med Phys Radiation Measurements For the acceptance test and annual quality assurance of the Leksell Gamma Unit, measurement of the beam accuracy, defined as a distance between mechanical and radiological isocenters, poses a challenge to medical physicists. The specification for the beam accuracy is within 0.5 mm for the 4‐mm collimator helmet. In this report, we introduce a simple technique to analyze the beam accuracy by using a conventional film densitometer plus mathematical modeling. A small piece of film was placed inside the film cassette containing a sharp needle. The needle is located such that its tip is exactly positioned at the mechanical isocenter. Before exposure, the film was pierced by the needle. Density profile was measured by using a densitometer with a spatial resolution of 0.8 mm. The profile was then fitted to a model of the two Gaussian functions. One is for the radiation field profile, the other for a dip caused by the narrow hole. The difference between the centers of the two Gaussian functions defines the deviation of the beam accuracy from the mechanical center of the unit. The deviations for x, y, and z directions from one of our annual measurements are 0.032, 0.054, and 0.195 mm, respectively. The combined deviation is 0.20 mm, which is well within the specification and in excellent agreement with the results from the manufacture's laser measurement. This technique provides a simple, accurate and practical tool for measurement of the beam accuracy in the acceptance test and annual quality assurance of the Leksell Gamma Unit. PACS number(s): 87.66.–a, 87.53.–j John Wiley and Sons Inc. 2000-01-01 /pmc/articles/PMC5726164/ /pubmed/11674816 http://dx.doi.org/10.1120/jacmp.v1i1.2652 Text en © 2000 The Authors. This is an open access article under the terms of the Creative Commons Attribution (http://creativecommons.org/licenses/by/3.0/) License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.
spellingShingle Radiation Measurements
Yu, Cheng
Petrovich, Zbigniew
Luxton, Gary
Quality Assurance of Beam Accuracy for Leksell Gamma Unit
title Quality Assurance of Beam Accuracy for Leksell Gamma Unit
title_full Quality Assurance of Beam Accuracy for Leksell Gamma Unit
title_fullStr Quality Assurance of Beam Accuracy for Leksell Gamma Unit
title_full_unstemmed Quality Assurance of Beam Accuracy for Leksell Gamma Unit
title_short Quality Assurance of Beam Accuracy for Leksell Gamma Unit
title_sort quality assurance of beam accuracy for leksell gamma unit
topic Radiation Measurements
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5726164/
https://www.ncbi.nlm.nih.gov/pubmed/11674816
http://dx.doi.org/10.1120/jacmp.v1i1.2652
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