Sci—Thur PM: YIS — 10: A new optically encoded single‐fiber plastic scintillation detector for multi‐point radiation dosimetry

Purpose: To develop a new multi‐point plastic scintillation detector (mPSD) that allows for simultaneous dose measurements at multiple points and uses a single optical guide. Materials and Methods: Two different prototypes were built. A two‐point mPSD was built and light discrimination was based on the use of multiple color filters at the outputs of a network of optical fiber splitters. Light intensity was measured by an EMCCD camera. For the three‐point mPSD, the light discrimination setup was replaced by a low‐noise spectrometer. Depth‐dose and profiles measurements were obtained on a 6 MV photon beam with the mPSDs inside a water phantom. An ion chamber was also used for comparison purpose. Finally, the three‐point mPSD was tested under an Ir‐192 high‐dose‐rate (HDR) brachytherapy dose delivery and compared to the treatment planning system. Results: A good agreement was found between the measured and expected dose for both mPSDs. The average relative differences to the ion chamber measurement for the two‐point mPSD were of (2.4 ± 1.6)% and (1.3 ± 0.8)%. For the three‐point mPSD, these differences were of (2.3±1.1)%, (1.6±0.4)% and (0.32±0.19)%. The latter mPSD was shown very versatile, being able to measure dose from HDR brachytherapy with an average accuracy of (2.3±1.0)% per catheter. Conclusions: The practical feasibility of mPSDs using a single optical guide has been demonstrated under irradiation from a 6 MV photon beam and an Ir‐192 HDR brachytherapy source. Their application for pre‐treatment quality assurance and in vivo dosimetry will be various.