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X-ray computed tomography for performing polymer gel dosimetry : a feasibility study Hilts, Michelle Louise
Abstract
Radiation therapy treatment of cancer is increasingly concerned with delivering dose distributions that conform to the tumour volume. For verification of treatment planning computer dose calculations, these conformal therapies demand an accurate, sensitive, high resolution three dimensional (3D) dosimeter. Polymer gels are novel, inherently 3D, tissue equivalent radiation dosimeters. Traditionally, dose distributions recorded in polymer gel are read out using magnetic resonance imaging (MRI). Presented here is a feasibility study on a new 3D dosimetry technique that uses x-ray computed tomography (CT) to read dosimetric information from polymer gels. The technique exploits a gel density change that occurs in response to ionizing radiation. This study has three main goals: 1) to develop a protocol for producing quality CT polymer gel images; 2) to evaluate the nature and reproducibility of the dosimeter's CT number (JVcr)-dose response; and 3) to compare this technique with MRI polymer gel dosimetry. A quantitative discussion of the density changes occurring in the gel in response to ionization radiation is also provided. Experiments are conducted using a PAG (polyacrylamide and gelatin) gel dosimeter irradiated with four intersecting 10 M V photon beams. The NCT -dose response is found to be linear and reproducible over the range of 200 to 1OOOcGy. At room temperature the response is (8.7 ± 0.3)xl0⁻³ NCT/cGy resulting in a limited dose resolution, - 100 cGy. Gel temperature during imaging is determined to have only a small effect, 0.3%/°C, on the dose response. Spatial resolution is 0.5 mm in the image plane and 10mm-1mm (depending on noise requirements) in the third dimension. Despite the low dose resolution, preliminary results indicate this technique provides accurate localization of high dose regions and, given the availability and speed of CT imaging, has the potential to be a valuable and practical tool for radiation therapy clinics.
Item Metadata
Title |
X-ray computed tomography for performing polymer gel dosimetry : a feasibility study
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Creator | |
Publisher |
University of British Columbia
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Date Issued |
1999
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Description |
Radiation therapy treatment of cancer is increasingly concerned with delivering dose
distributions that conform to the tumour volume. For verification of treatment planning
computer dose calculations, these conformal therapies demand an accurate, sensitive, high
resolution three dimensional (3D) dosimeter. Polymer gels are novel, inherently 3D, tissue
equivalent radiation dosimeters. Traditionally, dose distributions recorded in polymer gel are
read out using magnetic resonance imaging (MRI). Presented here is a feasibility study on a
new 3D dosimetry technique that uses x-ray computed tomography (CT) to read dosimetric
information from polymer gels. The technique exploits a gel density change that occurs in
response to ionizing radiation. This study has three main goals: 1) to develop a protocol for
producing quality CT polymer gel images; 2) to evaluate the nature and reproducibility of the
dosimeter's CT number (JVcr)-dose response; and 3) to compare this technique with MRI
polymer gel dosimetry. A quantitative discussion of the density changes occurring in the gel
in response to ionization radiation is also provided. Experiments are conducted using a PAG
(polyacrylamide and gelatin) gel dosimeter irradiated with four intersecting 10 M V photon
beams. The NCT -dose response is found to be linear and reproducible over the range of 200
to 1OOOcGy. At room temperature the response is (8.7 ± 0.3)xl0⁻³ NCT/cGy resulting in a
limited dose resolution, - 100 cGy. Gel temperature during imaging is determined to have
only a small effect, 0.3%/°C, on the dose response. Spatial resolution is 0.5 mm in the image
plane and 10mm-1mm (depending on noise requirements) in the third dimension. Despite
the low dose resolution, preliminary results indicate this technique provides accurate
localization of high dose regions and, given the availability and speed of CT imaging, has the
potential to be a valuable and practical tool for radiation therapy clinics.
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Extent |
6284197 bytes
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Genre | |
Type | |
File Format |
application/pdf
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Language |
eng
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Date Available |
2009-06-25
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Provider |
Vancouver : University of British Columbia Library
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Rights |
For non-commercial purposes only, such as research, private study and education. Additional conditions apply, see Terms of Use https://open.library.ubc.ca/terms_of_use.
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DOI |
10.14288/1.0089158
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URI | |
Degree | |
Program | |
Affiliation | |
Degree Grantor |
University of British Columbia
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Graduation Date |
1999-11
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Campus | |
Scholarly Level |
Graduate
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Aggregated Source Repository |
DSpace
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Item Media
Item Citations and Data
Rights
For non-commercial purposes only, such as research, private study and education. Additional conditions apply, see Terms of Use https://open.library.ubc.ca/terms_of_use.