skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: Correction method for in-air output ratio for output variations occurring with changes in backscattered radiation

Abstract

Purpose: The in-air output ratio (S{sub c}) for a rectangular field is usually obtained using an equivalent square field formula. However, it is well-known that S{sub c} obtained using an equivalent square field formula differs slightly from the measured S{sub c}. Though several correction methods have been suggested for the monitor-backscatter effect, the authors propose a more simple correction method for a rectangular field. Methods: For rectangular fields and equivalent square fields, the authors assumed that the output variation was the product of six output variations for each backscattering area at the top of the collimator jaws, and the correction factor was the ratio of the output variation for a rectangular field to the output variation for an equivalent square field. The output variation was measured by using a telescope measurement. Results: The differences between the measured and corrected S{sub c} ranged from -0.20% to 0.28% for symmetric rectangular fields by applying the correction factor to S{sub c} obtained using an equivalent square field formula. This correction method is also available for asymmetric rectangular fields. Conclusions: The authors propose a method to correct S{sub c} obtained using an equivalent square field formula, and a method to obtain the output variationmore » for a field defined by collimator jaws.« less

Authors:
; ;  [1]
  1. Research Center Hospital for Charged Particle Therapy, National Institute of Radiological Sciences, 4-9-1, Anagawa, Inage-ku, Chiba 263-8555 (Japan)
Publication Date:
OSTI Identifier:
22098754
Resource Type:
Journal Article
Journal Name:
Medical Physics
Additional Journal Information:
Journal Volume: 39; Journal Issue: 2; Other Information: (c) 2012 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:
62 RADIOLOGY AND NUCLEAR MEDICINE; ASYMMETRY; BACKSCATTERING; COLLIMATORS; CORRECTIONS; RADIOTHERAPY; SYMMETRY

Citation Formats

Tajiri, Minoru, Tokiya, Yuji, Watanabe, Kazuhiro, International University of Health and Welfare, 1-4-3, Mita, Minato-ku, Tokyo 108-8329, and Research Center Hospital for Charged Particle Therapy, National Institute of Radiological Sciences, 4-9-1, Anagawa, Inage-ku, Chiba 263-8555. Correction method for in-air output ratio for output variations occurring with changes in backscattered radiation. United States: N. p., 2012. Web. doi:10.1118/1.3675405.
Tajiri, Minoru, Tokiya, Yuji, Watanabe, Kazuhiro, International University of Health and Welfare, 1-4-3, Mita, Minato-ku, Tokyo 108-8329, & Research Center Hospital for Charged Particle Therapy, National Institute of Radiological Sciences, 4-9-1, Anagawa, Inage-ku, Chiba 263-8555. Correction method for in-air output ratio for output variations occurring with changes in backscattered radiation. United States. https://doi.org/10.1118/1.3675405
Tajiri, Minoru, Tokiya, Yuji, Watanabe, Kazuhiro, International University of Health and Welfare, 1-4-3, Mita, Minato-ku, Tokyo 108-8329, and Research Center Hospital for Charged Particle Therapy, National Institute of Radiological Sciences, 4-9-1, Anagawa, Inage-ku, Chiba 263-8555. 2012. "Correction method for in-air output ratio for output variations occurring with changes in backscattered radiation". United States. https://doi.org/10.1118/1.3675405.
@article{osti_22098754,
title = {Correction method for in-air output ratio for output variations occurring with changes in backscattered radiation},
author = {Tajiri, Minoru and Tokiya, Yuji and Watanabe, Kazuhiro and International University of Health and Welfare, 1-4-3, Mita, Minato-ku, Tokyo 108-8329 and Research Center Hospital for Charged Particle Therapy, National Institute of Radiological Sciences, 4-9-1, Anagawa, Inage-ku, Chiba 263-8555},
abstractNote = {Purpose: The in-air output ratio (S{sub c}) for a rectangular field is usually obtained using an equivalent square field formula. However, it is well-known that S{sub c} obtained using an equivalent square field formula differs slightly from the measured S{sub c}. Though several correction methods have been suggested for the monitor-backscatter effect, the authors propose a more simple correction method for a rectangular field. Methods: For rectangular fields and equivalent square fields, the authors assumed that the output variation was the product of six output variations for each backscattering area at the top of the collimator jaws, and the correction factor was the ratio of the output variation for a rectangular field to the output variation for an equivalent square field. The output variation was measured by using a telescope measurement. Results: The differences between the measured and corrected S{sub c} ranged from -0.20% to 0.28% for symmetric rectangular fields by applying the correction factor to S{sub c} obtained using an equivalent square field formula. This correction method is also available for asymmetric rectangular fields. Conclusions: The authors propose a method to correct S{sub c} obtained using an equivalent square field formula, and a method to obtain the output variation for a field defined by collimator jaws.},
doi = {10.1118/1.3675405},
url = {https://www.osti.gov/biblio/22098754}, journal = {Medical Physics},
issn = {0094-2405},
number = 2,
volume = 39,
place = {United States},
year = {Wed Feb 15 00:00:00 EST 2012},
month = {Wed Feb 15 00:00:00 EST 2012}
}