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Title: Development and characterization of a tissue equivalent plastic scintillator based dosimetry system

Abstract

High precision techniques in radiation therapy, such as intensity modulated radiation therapy, offer the potential for improved target coverage and increased normal tissue sparing compared with conformal radiotherapy. The complex fluence maps used in many of these techniques, however, often lead to more challenging quality assurance with dose verification being labor-intensive and time consuming. A prototype dose verification system has been developed using a tissue equivalent plastic scintillator that provides easy-to-acquire, rapid, digital dose measurements in a plane perpendicular to the beam. The system consists of a water-filled Lucite phantom with a scintillator screen built into the top surface. The phantom contains a silver coated plastic mirror to reflect scintillation light towards a viewing window where it is captured using a charge coupled device camera and a personal computer. Optical photon spread is removed using a microlouvre optical collimator and by deconvolving a glare kernel from the raw images. A characterization of the system was performed that included measurements of linear output response, dose rate dependence, spatial linearity, effective pixel size, signal uniformity and both short- and long-term reproducibility. The average pixel intensity for static, regular shaped fields between 3 cmx3 cm and 12 cmx12 cm imaged with the systemmore » was found to be linear in the dose delivered with linear regression analysis yielding a correlation coefficient r{sup 2}>0.99. Effective pixel size was determined to be 0.53 mm/pixel. The system was found to have a signal uniformity of 5.6% and a long-term reproducibility/stability of 1.7% over a 6 month period. The system's ability to verify a dynamic treatment field was evaluated using 60 deg. dynamic wedged fields and comparing the results to two-dimensional film dosimetry. Results indicate agreement with two-dimensional film dosimetry distributions within 8% inside the field edges. With further development, this system promises to provide a fast, directly digital, and tissue equivalent alternative to current dose verification systems.« less

Authors:
; ;  [1];  [2];  [2]
  1. Department of Medical Physics, BC Cancer Agency, Vancouver, British Columbia, V5Z 4E6 (Canada)
  2. (Canada)
Publication Date:
OSTI Identifier:
20774990
Resource Type:
Journal Article
Resource Relation:
Journal Name: Medical Physics; Journal Volume: 33; Journal Issue: 1; Other Information: DOI: 10.1118/1.2140118; (c) 2006 American Association of Physicists in Medicine; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
62 RADIOLOGY AND NUCLEAR MEDICINE; 46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND TECHNOLOGY; COLLIMATORS; DOSE RATES; FILM DOSIMETRY; LUCITE; PERSONAL COMPUTERS; PHANTOMS; PHOTONS; QUALITY ASSURANCE; RADIATION DOSES; RADIOTHERAPY; REGRESSION ANALYSIS; SOLID SCINTILLATION DETECTORS; VERIFICATION

Citation Formats

Petric, M.P., Robar, J.L., Clark, B.G., Department of Medical Physics, Nova Scotia Cancer Centre, Halifax, Nova Scotia, B3H 1V7, and Department of Medical Physics, BC Cancer Agency, Vancouver, British Columbia, V5Z 4E6. Development and characterization of a tissue equivalent plastic scintillator based dosimetry system. United States: N. p., 2006. Web. doi:10.1118/1.2140118.
Petric, M.P., Robar, J.L., Clark, B.G., Department of Medical Physics, Nova Scotia Cancer Centre, Halifax, Nova Scotia, B3H 1V7, & Department of Medical Physics, BC Cancer Agency, Vancouver, British Columbia, V5Z 4E6. Development and characterization of a tissue equivalent plastic scintillator based dosimetry system. United States. doi:10.1118/1.2140118.
Petric, M.P., Robar, J.L., Clark, B.G., Department of Medical Physics, Nova Scotia Cancer Centre, Halifax, Nova Scotia, B3H 1V7, and Department of Medical Physics, BC Cancer Agency, Vancouver, British Columbia, V5Z 4E6. Sun . "Development and characterization of a tissue equivalent plastic scintillator based dosimetry system". United States. doi:10.1118/1.2140118.
@article{osti_20774990,
title = {Development and characterization of a tissue equivalent plastic scintillator based dosimetry system},
author = {Petric, M.P. and Robar, J.L. and Clark, B.G. and Department of Medical Physics, Nova Scotia Cancer Centre, Halifax, Nova Scotia, B3H 1V7 and Department of Medical Physics, BC Cancer Agency, Vancouver, British Columbia, V5Z 4E6},
abstractNote = {High precision techniques in radiation therapy, such as intensity modulated radiation therapy, offer the potential for improved target coverage and increased normal tissue sparing compared with conformal radiotherapy. The complex fluence maps used in many of these techniques, however, often lead to more challenging quality assurance with dose verification being labor-intensive and time consuming. A prototype dose verification system has been developed using a tissue equivalent plastic scintillator that provides easy-to-acquire, rapid, digital dose measurements in a plane perpendicular to the beam. The system consists of a water-filled Lucite phantom with a scintillator screen built into the top surface. The phantom contains a silver coated plastic mirror to reflect scintillation light towards a viewing window where it is captured using a charge coupled device camera and a personal computer. Optical photon spread is removed using a microlouvre optical collimator and by deconvolving a glare kernel from the raw images. A characterization of the system was performed that included measurements of linear output response, dose rate dependence, spatial linearity, effective pixel size, signal uniformity and both short- and long-term reproducibility. The average pixel intensity for static, regular shaped fields between 3 cmx3 cm and 12 cmx12 cm imaged with the system was found to be linear in the dose delivered with linear regression analysis yielding a correlation coefficient r{sup 2}>0.99. Effective pixel size was determined to be 0.53 mm/pixel. The system was found to have a signal uniformity of 5.6% and a long-term reproducibility/stability of 1.7% over a 6 month period. The system's ability to verify a dynamic treatment field was evaluated using 60 deg. dynamic wedged fields and comparing the results to two-dimensional film dosimetry. Results indicate agreement with two-dimensional film dosimetry distributions within 8% inside the field edges. With further development, this system promises to provide a fast, directly digital, and tissue equivalent alternative to current dose verification systems.},
doi = {10.1118/1.2140118},
journal = {Medical Physics},
number = 1,
volume = 33,
place = {United States},
year = {Sun Jan 15 00:00:00 EST 2006},
month = {Sun Jan 15 00:00:00 EST 2006}
}