TU‐C‐108‐05: High Density Organic Scintillator Arrays for High Resolution Stereotactic Body Radiation Therapy Dosimetry

Abstract

Purpose: Radiation oncology patients receiving stereotactic body radiation therapy (SBRT) are treated with high dose and high dose rate treatment procedures in which delivered dose should be recorded, and verified for quality assurance and patient safety. We implemented a high resolution scintillating fiber detector array to perform high resolution dosimetry of SBRT fields. Materials: Scintillating fibers have a water equivalent attenuation coefficient, excellent reproducibility, stability and a linear response versus dose, do not require any polarizing voltage, and are water impermeable. We constructed a high resolution dosimeter based on an array of sub‐millimeter organic fiber sensors mounted on a supporting frame that provides support, alignment, and buildup material. The fiber detector interface consists of a high density linear array of high speed linear photodetectors. The analog output is transmitted to a high throughput parallel data acquisition system integrated with a dedicated computer for signal processing, analysis, and recording. The detector was specially designed to perform high resolution dosimetric verification of small SBRT fields delivered with conventional dose rates (600 MU/min) to high dose rate flattening filter free beams (up to 2400 MU/min). Results: We determined fiber sensor sensitivity and linearity response with respect to beam intensity field size and dose. Detector spatial resolution is 0.5 mm and linearity response with respect to beam intensity and field size was within 2% for photon beams from 6MV to 18 MV and electron beams from 6 MeV to 20 MeV. Spatial beam profiles were compared with film dosimetry showing excellent agreement within 3% in the penumbra region. Conclusions: The development of this technology addresses the need for high resolution dosimeters for SBRT. The developed detector provides accurate dose, beam localization, and beam profile verification and will be a valuable tool for quality assurance of SBRT treatments.