Sci—Thur PM: YIS — 07: A Two Dimensional Plastic Scintillation Detector Array for Quality Assurance of Intensity Modulated Radiation Therapy

Abstract

Purpose: The goals of this study are: 1) to present a novel two Dimensional Plastic Scintillation Detector array (2D‐PSD) for measurements of complex dose distributions, 2) to demonstrate that the 2D‐PSD can be used for high accuracy dose measurements for variable beam incidences. Methods and Materials: The 2D‐PSD consists of 781 PSDs inserted vertically in a plastic water slab covering a 26×26 cm2 region. The prototype is built entirely from nearly water equivalent plastic materials. To characterize the angular dependence of the 2D‐PSD, the detector array was irradiated with a square field size 10×10 cm2 using variable beam incidences from 0° to 120°. Furthermore, a clinical head and neck IMRT plan composed of nine beams was delivered on the 2D‐PSD by keeping the gantry of the linear accelerator fixed at 0°. The dose distributions measured with the 2D‐PSD were compared to calculations from a treatment planning system (Pinnacle3, Philips Medical Systems) on a CT scan of the 2D‐PSD and with measurements taken with an ionization chambers array (MatriXX Evolution, IBA Dosimetry). Results: The results from the angular dependence study indicate an excellent agreement between the measured and calculated dose distributions. The gamma evaluation of the IMRT plan delivered was successful for 98.5% of the detectors for a dose tolerance of 3% and a distance to agreement of 3 mm. Conclusion: The results presented in this work suggest that the developed 2D‐PSD could be used as a quality assurance tool for IMRT and arc therapy patient plan verification.