The sophistication of radiation therapy delivery techniques at Mary Bird Perkins Cancer Center (MBPCC) creates the need for an advanced dosimetric system that can quantify and verify the dose distributions in three-dimensions. Current dosimetric systems perform this dose analysis in only one or two dimensions. This paper evaluates the application of BANG-3 polymer gel dosimetry to quantify the 3-D dose distribution of Intensity-Modulated Radiation Therapy (IMRT) using a "step and shoot" approach. The gel was irradiated by 10 MV photons at a dose rate of 400 MU/min. Relaxation rate maps were computed from proton density and T<sub>2</sub>-weighted magnetic resonance images acquired with a GE Horizon 1.5T scanner; scans were performed 5 days and 2 months post-irradiation. The dose distribution within the gel was compared to the dose distribution calculated by the Pinnacle<sup>3</sup> planning system. Three techniques were used for analysis: image subtraction, dose-volume analysis and contour analysis. Also, a dose correction factor was used to attempt to correct for excess dose delivered to the gel as the gels were erroneously placed in the treatment room two days prior to irradiation. Corrected 5-day post-irradiation dose maps show reasonable agreement with the Pinnacle<sup>3</sup> plan. The absolute measurement error was +/-50 cGy; however, the relative errors were large compared to the total dose of 2 Gy delivered to the gel. Delivering a larger total dose should reduce the relative error to a reasonable magnitude. Exposure to light and other environmental factors caused substantial additional polymerization with time. The results of this project indicate that polymer gel dosimetry could be a useful routine 3D dosimetric technique at MBPCC. However, utilizing a commercial scanning service may simplify use of the gels.
| Identifer | oai:union.ndltd.org:LSU/oai:etd.lsu.edu:etd-0305103-143757 |
| Date | 11 March 2003 |
| Creators | Bruce, Paul Anthony |
| Contributors | Sheldon Johnson, Mark Williams, Thomas Kirby, Oscar Hidalgo, Kenneth Matthews |
| Publisher | LSU |
| Source Sets | Louisiana State University |
| Language | English |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | http://etd.lsu.edu/docs/available/etd-0305103-143757/ |
| Rights | unrestricted, I hereby grant to LSU or its agents the right to archive and to make available my thesis or dissertation in whole or in part in the University Libraries in all forms of media, now or hereafter known. I retain all proprietary rights, such as patent rights. I also retain the right to use in future works (such as articles or books) all or part of this thesis or dissertation. |
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