(Sunday, 7/12/2020) [Eastern Time (GMT-4)]
Room: AAPM ePoster Library
Purpose: The purpose of this work is to evaluate the HYPERSCINT scintillation dosimetry research platform (Medscint Inc., Quebec City, Canada) designed for clinical QA for use in in-vivo dosimetry measurements.
Methods: The pre-clinical evaluation of the scintillator was performed using a Varian TrueBeam to irradiate the scintillator in a water phantom. Dependency on energy, field size, dose rate, temperature, angle, depth, and radiation type were measured in a water tank and compared to calibration data. From commissioning and annual QA. The clinical evaluation was first performed on 2 cadaver dogs, and then in three companion animal dogs receiving radiation therapy for nasal tumors. A treatment planning CT scan was performed for cadavers and clinical patients. Prior to treatment, the probe was inserted into the radiation field. Radiation was then delivered and measured with the scintillator. For cadavers, an intentional shift in patient position was made before treatment to simulate an error in dose delivery.
Results: Measured dose differed as follows: photon energies 0.09 – 3.03%, field size -0.8 – 0.43, dose rate 0.3 – 3.6%, temperature dependency required a correction factor of 0.11/°C, angular dependency -0.01 – 1.18%, depth dose measurement -1.14 – 0.36%. Electron data needs to be further evaluated but likely requires a different calibration than photons. In two cadavers intentionally treated in the wrong position the scintillator detected the new dose at 99.3 and 101.4% of the expected dose. In three clinical patients treated in multiple fractions the detected dose ranged from 98.33 – 103.15%.
Conclusion: Initial results indicate that the HYPERSCINT is performing with similar accuracy and reproducibility than other established devices for in-vivo dosimetry. Additional work needs to be done to evaluate temperature and dose rate dependency under clinical conditions.
Funding Support, Disclosures, and Conflict of Interest: S. Dieterich has received research funding from Varian unrelated to this work.
Keywords
In Vivo Dosimetry, Scintillators, Quality Assurance
Taxonomy
TH- External Beam- Photons: portal dosimetry, in-vivo dosimetry and dose reconstruction
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