(Sunday, 7/29/2018) 4:00 PM - 4:55 PM
Room: Room 209
Purpose: Multipoint plastic scintillator detectors have been previously studied in HDR brachytherapy but with important limitations.This study aims to demonstrate that with proper optimization of the signal collection chain, mPSD increased performance are suitable for dose measurements covering 3 orders of magnitude in dose rate.
Methods: A 3 points mPSD was constructed and characterized in HDR brachytherapy.Scintillators BCF-60,BCF-12 and BCF-10 constituted the mPSD sensitive volume.Scintillation light is transmitted through a single 1 mm diameter clear optical fibre and read by an assembly of photomultipliers tubes (PMTs) coupled to dichroic mirrors and filters.Each component is further numerically optimized to allow for signal deconvolution using a multispectral approach, taking care of Cerenkov stem effect.PMTs are independently controlled from the 192Ir source and read simultaneously using NI-DAQ board.Dose measurements in terms of distance and angle to the source were carried out according to TG43 recommendations.The system performance was quantified in terms of signal to noise ratio (SNR) and signal to background ratio (SBR).The triangulation principle was used to report the source dwell position relative to the planned one.
Results: Deviations between the mPSD measurements and TG-43 are below 5% in the range 0.5-5 cm from the source.In all the explored measurement conditions,the system was able to properly differentiate the produced scintillation signal from the background one: SNR>5 and SBR>3 for all dose rates (6-2000 mGy/s).No angular dependences were observed. The optimized system was able to provide an average source location with a standard deviation no greater than 1.3 mm.The observed difference relative to the expected value was 0.11 and 1.1 mm in X and Z direction respectively.
Conclusion: mPSD have potential clinical applications beyond currently available dosimeters.A 3 points mPSD was constructed and optimized for HDR brachytherapy dosimetry,enabling real time dose and source position reporting over a wide range of dose rate conditions.
Funding Support, Disclosures, and Conflict of Interest: Acknowledges partial support by the CREATE Medical Physics Research Training Network grant of the Natural Sciences and Engineering Research Council (Grant number: 432290)
Keywords
Brachytherapy, In Vivo Dosimetry, Scintillators
Taxonomy
Not Applicable / None Entered.
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