SU-D-108-03: Evaluation of the Feasibility of a Novel Radiochromic Dosimetry System for In-Vivo Dose Verification in Organs at Risk in HDR Intracavitary Gynecological Brachytherapy.

PURPOSE: To evaluate the feasibility of a novel radiochromic dosimetry system for in-vivo dose verification in organs at risk in HDR intracavitary gynecological brachytherapy. METHODS: Novel, small cylindrical PRESAGE dosimeters (4mm in diameter by 20mm in height) were attached to intracavitary HDR brachytherapy applicators near the rectum and bladder of three patients undergoing Ir-192 HDR brachytherapy treatments. Two methods of dose-readout were investigated (i) a volume averaged readout by spectrophotometer, and (ii) 2D projection imaging in a high-resolution (50 micron) telecentric optical system. Both readout techniques were benchmarked against a gold standard. The gold standard consisted of spectrophotometer readout of precision 1×1×4cm optical cuvettes filled with PRESAGE, and irradiated to known doses in a 6 MV photon beam. Temperature corrections were required to account for increased PRESAGE sensitivity at body temperature. Estimated doses were compared with measured dose distributions in Eclipse. RESULTS: Examination of the change in optical density between dosimeters and cuvettes shows a linear relationship in sensitivity between 1-15 Gy with a 95% confidence interval in the slope (0.8703 +/- 0.0192). Patient data showed a 0 % and 2.8% difference in estimated doses vs. Eclipse measurements in the bladder and rectum, respectively. CONCLUSION: This work presents the spectrophotometer/optical scanning system as a viable dosimetry system, which can provide in-vivo dose verification in intracavitary HDR brachytherapy. Further work needs to be done in regard to dosimeter positioning in patient treatments. NIH Grant RO1CA100835.

Duke Scholars

Author Sheridan Griffin Meltsner Radiation Oncology

Author Junzo Paul Chino Radiation Oncology

Author Oana Craciunescu Radiation Oncology

Author Mark Oldham Radiation Oncology