Program Information
Feasibility of Real-Time Dosimetry for HDR Prostate Brachytherapy Using a Nano-Fiber Optic Detector
M Rokni1*, A Rodrigues2, B Moore1, T Yoshizumi2, O Craciunescu2, (1) Duke University, Durham, NC, (2) Duke University Medical Center, Durham, NC
Presentations
TU-FG-205-8 (Tuesday, August 1, 2017) 1:45 PM - 3:45 PM Room: 205
Purpose: Treatment errors can occur in high dose rate (HDR) prostate brachytherapy treatment (ICRP report number 97), but current detector methodology only reports post-treatment errors. We investigate the feasibility of a nano-fiber optic detector (NanoFOD) for real-time dosimetry of HDR prostate brachytherapy with the end point of identifying and reducing potential errors. The NanoFOD consists of an inorganic nano-crystalline scintillator that has been fixed on an optical fiber, and is small enough to be placed in-vivo and measure point doses to sub-millimeter resolution.
Methods: The NanoFOD was calibrated for an Ir-192 HDR source via a distance calibration curve measured by determining detector response, in water, at source-to-detector distances between 0 and 90mm. The calibration tank was large enough to meet scatter requirements outlined in the AAPM TG-43 report, so a distance response curve could be calculated using this formalism. A clinical prostate treatment with a prescription dose of 15 Gy and 16 needles was created using Vitesse 3.0 (Varian Corp.) and delivered to a prostate training phantom (CIRS 053G). Two additional needles containing NanoFODs were placed in the central region of the prostate prior to treatment, allowing dosimetry to be displayed in real-time during delivery. Comparison between the planned dose from the treatment planning system and the measured dose from the two Nano-FOD locations was performed.
Results: Dose differences between the planned and measured doses were 25.8% (18.14 Gy vs. 22.82 Gy) and 19.4% (17.81 Gy vs. 21.27 Gy) for NanoFOD 1 and 2, respectively.
Conclusion: The NanoFOD detector is capable of real-time dosimetry and could be useful in quality assurance in HDR prostate brachytherapy. Future work will focus on improving the accuracy of measurements through improved calibration techniques and isolating uncertainties having to do with the complexity of the overall US-based HDR prostate treatment.
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