3D dosimetry for proton therapy

Abstract

We have been developing novel 3-dimensional (3D) detector systems using organic plastic and liquid scintillators to measure and image the dose distribution from proton therapy beams in near-real time. Proof-of-concept and initial feasibility studies using a single charge-coupled device camera have already been conducted. Our recent studies focused on the characterization of scanning proton beams used for patient treatments using a 3D liquid scintillator-based detector system with a set of scientific-complementary metal-oxide-semiconductor (sCMOS) cameras. The basic concept consists of using a large volume of a solid or liquid scintillator to measure or image the dose distributions from proton beams in 3D. We recently developed a large liquid scintillator-based detector system consisting of a 20 - 20 - 20cm transparent acrylic tank filled with a water-equivalent, commercially available liquid scintillator that generates scintillation light when irradiated with protons. To track rapid spatial and dose variations in spot-scanned proton beams, we used 3 high-speed sCMOS cameras to image the scintillation light signals from 3 orthogonal projections in cine mode. Furthermore, we developed a new image acquisition approach that synchronized camera imaging times with dynamic pencil-beam deliveries to efficiently capture the dose and therefore enable accurate dosimetric calculations. This system was fully developed and characterized at the Proton Therapy Center at The University of Texas MD Anderson Cancer Center. We show that such systems can provide fast and accurate measurements of the range, lateral profile, and lateral position of scanning proton beams with excellent spatial resolution (0.21 mm). We also demonstrate that such detectors can rapidly measure proton beam characteristics and intensities at multiple energies, which makes them an ideal tool for scanned proton-beam systems, beam quality assurance studies, and verification of patient treatment delivery.