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Title: Characterization of electron contamination in megavoltage photon beams

Abstract

The purpose of the present study is to characterize electron contamination in photon beams in different clinical situations. Variations with field size, beam modifier (tray, shaping block) and source-surface distance (SSD) were studied. Percentage depth dose measurements with and without a purging magnet and replacing the air by helium were performed to identify the two electron sources that are clearly differentiated: air and treatment head. Previous analytical methods were used to fit the measured data, exploring the validity of these models. Electrons generated in the treatment head are more energetic and more important for larger field sizes, shorter SSD, and greater depths. This difference is much more noticeable for the 18 MV beam than for the 6 MV beam. If a tray is used as beam modifier, electron contamination increases, but the energy of these electrons is similar to that of electrons coming from the treatment head. Electron contamination could be fitted to a modified exponential curve. For machine modeling in a treatment planning system, setting SSD at 90 cm for input data could reduce errors for most isocentric treatments, because they will be delivered for SSD ranging from 80 to 100 cm. For very small field sizes, air-generated electronsmore » must be considered independently, because of their different energetic spectrum and dosimetric influence.« less

Authors:
; ; ; ; ; ;  [1]
  1. Department of Medical Physics, Instituto Galego de Medicina Tecnica, Hospital do Meixoeiro, 36200, Vigo (Spain)
Publication Date:
OSTI Identifier:
20634682
Resource Type:
Journal Article
Journal Name:
Medical Physics
Additional Journal Information:
Journal Volume: 32; Journal Issue: 5; Other Information: DOI: 10.1118/1.1895793; (c) 2005 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; ABSORPTION SPECTRA; AIR; COMPUTERIZED SIMULATION; DEPTH DOSE DISTRIBUTIONS; ELECTRON DOSIMETRY; ELECTRON SOURCES; ERRORS; HELIUM; PHOTON BEAMS; PLANNING; PURIFICATION; RADIOTHERAPY

Citation Formats

Medina, Antonio Lopez, Teijeiro, Antonio, Garcia, Juan, Esperon, Jorge, Terron, J Antonio, Ruiz, Diego P, Carrion, Maria C, Department of Medical Physics, Hospital Universitario Virgen Macarena, 41009, Seville, and Department of Applied Physics, Faculty of Science, University of Granada, 18071, Granada. Characterization of electron contamination in megavoltage photon beams. United States: N. p., 2005. Web. doi:10.1118/1.1895793.
Medina, Antonio Lopez, Teijeiro, Antonio, Garcia, Juan, Esperon, Jorge, Terron, J Antonio, Ruiz, Diego P, Carrion, Maria C, Department of Medical Physics, Hospital Universitario Virgen Macarena, 41009, Seville, & Department of Applied Physics, Faculty of Science, University of Granada, 18071, Granada. Characterization of electron contamination in megavoltage photon beams. United States. https://doi.org/10.1118/1.1895793
Medina, Antonio Lopez, Teijeiro, Antonio, Garcia, Juan, Esperon, Jorge, Terron, J Antonio, Ruiz, Diego P, Carrion, Maria C, Department of Medical Physics, Hospital Universitario Virgen Macarena, 41009, Seville, and Department of Applied Physics, Faculty of Science, University of Granada, 18071, Granada. 2005. "Characterization of electron contamination in megavoltage photon beams". United States. https://doi.org/10.1118/1.1895793.
@article{osti_20634682,
title = {Characterization of electron contamination in megavoltage photon beams},
author = {Medina, Antonio Lopez and Teijeiro, Antonio and Garcia, Juan and Esperon, Jorge and Terron, J Antonio and Ruiz, Diego P and Carrion, Maria C and Department of Medical Physics, Hospital Universitario Virgen Macarena, 41009, Seville and Department of Applied Physics, Faculty of Science, University of Granada, 18071, Granada},
abstractNote = {The purpose of the present study is to characterize electron contamination in photon beams in different clinical situations. Variations with field size, beam modifier (tray, shaping block) and source-surface distance (SSD) were studied. Percentage depth dose measurements with and without a purging magnet and replacing the air by helium were performed to identify the two electron sources that are clearly differentiated: air and treatment head. Previous analytical methods were used to fit the measured data, exploring the validity of these models. Electrons generated in the treatment head are more energetic and more important for larger field sizes, shorter SSD, and greater depths. This difference is much more noticeable for the 18 MV beam than for the 6 MV beam. If a tray is used as beam modifier, electron contamination increases, but the energy of these electrons is similar to that of electrons coming from the treatment head. Electron contamination could be fitted to a modified exponential curve. For machine modeling in a treatment planning system, setting SSD at 90 cm for input data could reduce errors for most isocentric treatments, because they will be delivered for SSD ranging from 80 to 100 cm. For very small field sizes, air-generated electrons must be considered independently, because of their different energetic spectrum and dosimetric influence.},
doi = {10.1118/1.1895793},
url = {https://www.osti.gov/biblio/20634682}, journal = {Medical Physics},
issn = {0094-2405},
number = 5,
volume = 32,
place = {United States},
year = {Sun May 01 00:00:00 EDT 2005},
month = {Sun May 01 00:00:00 EDT 2005}
}