Evaluation of Plastic Scintillator Detector for In-Vivo Dosimetry
Abstract
Purpose
To develop and characterize plastic scintillator sheets for in-vivo dosimetry to measure entrance dose distributions for therapeutic photon, electron, and proton beams.
Methods
An in-vivo dosimeter made from plastic scintillator sheets was developed and evaluated using electron and photon beams from a TrueBeam linear accelerator and proton beams from a MEVION-S250i system. The detector consisted of plastic scintillator sheet of forming an effective cross-sectional area of 30×30cm² and 2mm thickness. The plastic scintillation sheets were placed on the top of a phantom and the scintillation light produced by radiation was collected with multiple cameras positioned around the detector. The recorded optical projections were subsequently used to reconstruct surface entrance dose distributions obtained by the plastic scintillation sheet.
Results
The developed detector functioned as a large, water-equivalent 2D dosimeter with an effective sensitive area of 30×30cm2. Dose projections acquired from multiple viewing angles enabled reconstruction of the surface dose distributions, extending beyond the planar measurements typically obtained with conventional 2D dosimeters. When tested with therapeutic spot-scanning proton beams, the system successfully detected and tracked individual beam spots, with temporal resolution limited by the camera acquisition rate of 30 frames per second. While the plastic scintillator itself provided intrinsically high spatial resolution, the accuracy of the reconstructed dose distributions was constrained by the camera digitization resolution (0.5 mm). Detector sensitivity was influenced by optical attenuation through the scintillator slabs and sensitivity of the cameras to the blue scintillation light and background from ambient light in the room.
Conclusion
This plastic scintillator–based 2D-dosimeter provides a tissue-equivalent detector with a large effective area and high spatial resolution, offering a novel detector for in-vivo dosimetry. This detector system has strong potential for broad clinical application in quality assurance procedures for therapeutic electron, photon, and proton beams.