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Title: The use of film dosimetry of the penumbra region to improve the accuracy of intensity modulated radiotherapy

Abstract

Accurate measurements of the penumbra region are important for the proper modeling of the radiation beam for linear accelerator-based intensity modulated radiation therapy. The usual data collection technique with a standard ionization chamber artificially broadens the measured beam penumbrae due to volume effects. The larger the chamber, the greater is the spurious increase in penumbra width. This leads to inaccuracies in dose calculations of small fields, including small fields or beam segments used in IMRT. This source of error can be rectified by the use of film dosimetry for penumbra measurements because of its high spatial resolution. The accuracy of IMRT calculations with a pencil beam convolution model in a commercial treatment planning system was examined using commissioning data with and without the benefit of film dosimetry of the beam penumbrae. A set of dose-spread kernels of the pencil beam model was calculated based on commissioning data that included beam profiles gathered with a 0.6-cm-i.d. ionization chamber. A second set of dose-spread kernels was calculated using the same commissioning data with the exception of the penumbrae, which were measured with radiographic film. The average decrease in the measured width of the 80%-20% penumbrae of various square fields of size 3-40more » cm, at 5 cm depth in water-equivalent plastic was 0.27 cm. Calculations using the pencil beam model after it was re-commissioned using film dosimetry of the penumbrae gave better agreement with measurements of IMRT fields, including superior reproduction of high dose gradient regions and dose extrema. These results show that accurately measuring the beam penumbrae improves the accuracy of the dose distributions predicted by the treatment planning system and thus is important when commissioning beam models used for IMRT.« less

Authors:
; ; ;  [1]
  1. Department of Radiation Oncology, McKay-Dee Hospital Center, 4401 Harrison Boulevard, Ogden, Utah 84403 (United States)
Publication Date:
OSTI Identifier:
20634616
Resource Type:
Journal Article
Journal Name:
Medical Physics
Additional Journal Information:
Journal Volume: 32; Journal Issue: 1; Other Information: DOI: 10.1118/1.1829246; (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; ACCURACY; BEAM PROFILES; COMMISSIONING; DOSEMETERS; FILM DOSIMETRY; IONIZATION CHAMBERS; KERNELS; LINEAR ACCELERATORS; PLANNING; RADIATION DOSE DISTRIBUTIONS; RADIATION DOSES; RADIOTHERAPY; SPATIAL RESOLUTION

Citation Formats

Arnfield, Mark R, Otto, Karl, Aroumougame, Vijayan R, Alkins, Ryan D, British Columbia Cancer Agency, 600 West 10th Avenue, Vancouver, British Columbia V5Z 4E6, St. Peter's Cancer Care Center, 317 S. Manning Boulevard, Suite 100, Albany, New York 12208, and University of British Columbia, 2733 Heather Street, Vancouver, British Columbia V5Z 3J5. The use of film dosimetry of the penumbra region to improve the accuracy of intensity modulated radiotherapy. United States: N. p., 2005. Web. doi:10.1118/1.1829246.
Arnfield, Mark R, Otto, Karl, Aroumougame, Vijayan R, Alkins, Ryan D, British Columbia Cancer Agency, 600 West 10th Avenue, Vancouver, British Columbia V5Z 4E6, St. Peter's Cancer Care Center, 317 S. Manning Boulevard, Suite 100, Albany, New York 12208, & University of British Columbia, 2733 Heather Street, Vancouver, British Columbia V5Z 3J5. The use of film dosimetry of the penumbra region to improve the accuracy of intensity modulated radiotherapy. United States. https://doi.org/10.1118/1.1829246
Arnfield, Mark R, Otto, Karl, Aroumougame, Vijayan R, Alkins, Ryan D, British Columbia Cancer Agency, 600 West 10th Avenue, Vancouver, British Columbia V5Z 4E6, St. Peter's Cancer Care Center, 317 S. Manning Boulevard, Suite 100, Albany, New York 12208, and University of British Columbia, 2733 Heather Street, Vancouver, British Columbia V5Z 3J5. 2005. "The use of film dosimetry of the penumbra region to improve the accuracy of intensity modulated radiotherapy". United States. https://doi.org/10.1118/1.1829246.
@article{osti_20634616,
title = {The use of film dosimetry of the penumbra region to improve the accuracy of intensity modulated radiotherapy},
author = {Arnfield, Mark R and Otto, Karl and Aroumougame, Vijayan R and Alkins, Ryan D and British Columbia Cancer Agency, 600 West 10th Avenue, Vancouver, British Columbia V5Z 4E6 and St. Peter's Cancer Care Center, 317 S. Manning Boulevard, Suite 100, Albany, New York 12208 and University of British Columbia, 2733 Heather Street, Vancouver, British Columbia V5Z 3J5},
abstractNote = {Accurate measurements of the penumbra region are important for the proper modeling of the radiation beam for linear accelerator-based intensity modulated radiation therapy. The usual data collection technique with a standard ionization chamber artificially broadens the measured beam penumbrae due to volume effects. The larger the chamber, the greater is the spurious increase in penumbra width. This leads to inaccuracies in dose calculations of small fields, including small fields or beam segments used in IMRT. This source of error can be rectified by the use of film dosimetry for penumbra measurements because of its high spatial resolution. The accuracy of IMRT calculations with a pencil beam convolution model in a commercial treatment planning system was examined using commissioning data with and without the benefit of film dosimetry of the beam penumbrae. A set of dose-spread kernels of the pencil beam model was calculated based on commissioning data that included beam profiles gathered with a 0.6-cm-i.d. ionization chamber. A second set of dose-spread kernels was calculated using the same commissioning data with the exception of the penumbrae, which were measured with radiographic film. The average decrease in the measured width of the 80%-20% penumbrae of various square fields of size 3-40 cm, at 5 cm depth in water-equivalent plastic was 0.27 cm. Calculations using the pencil beam model after it was re-commissioned using film dosimetry of the penumbrae gave better agreement with measurements of IMRT fields, including superior reproduction of high dose gradient regions and dose extrema. These results show that accurately measuring the beam penumbrae improves the accuracy of the dose distributions predicted by the treatment planning system and thus is important when commissioning beam models used for IMRT.},
doi = {10.1118/1.1829246},
url = {https://www.osti.gov/biblio/20634616}, journal = {Medical Physics},
issn = {0094-2405},
number = 1,
volume = 32,
place = {United States},
year = {Sat Jan 01 00:00:00 EST 2005},
month = {Sat Jan 01 00:00:00 EST 2005}
}