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Evaluation of the Feasibility of a Novel Radiochromic Dosimetry System for In-Vivo Dose Verification in Organs at Risk in HDR Intracavitary Gynecological Brachytherapy

A Vidovic

A Vidovic1*, Juang1, , B Steffey1, S Meltsner1, J Adamovics2, , J Chino1, O Craciunescu1, M Oldham1, , (1) Duke University Medical Center, Durham, NC, (2) John Adamovics, Skillman, NJ,

SU-D-108-3 Sunday 2:05PM - 3:00PM Room: 108

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 1x1x4cm 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.

Funding Support, Disclosures, and Conflict of Interest: NIH Grant RO1CA100835

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