Development and Testing of a 3D-Plastic Scintillator Detector for on-Board Proton Imaging
Abstract
Purpose
To design and test a three-dimensional detector for proton radiography and CT imaging using a volumetric plastic scintillator irradiated with therapeutic high energy proton beams.
Methods
A plastic scintillation detector was developed to acquire proton radiographs using 227MeV spot-scanning proton beams delivered by a MEVION-S250i proton therapy machines. The volumetric detector was made from a stack of plastic scintillator slabs measuring 30×30×20cm³. The detector was irradiated with high energy proton beams (20×20cm²) where the scintillation light was captured by 5 cameras positioned around the detector enclosed within a light-tight box. This imaging system performance was evaluated using a variety of anthropomorphic phantoms, including head, thorax, and pelvis models.
Results
The radiographic projections acquired from the different cameras enabled successful reconstruction of proton radiographs. Proton beam range measurements within the scintillator volume were used to derive water-equivalent thickness, which provided the basis for radiographic image contrast. The detector functioned as a large, water-equivalent 3D imaging system with an effective volume of approximately 30×30 ×20cm³, which can be expanded by adding additional scintillator layers. While the continuous scintillator medium provided high spatial and contrast resolution, proton radiographic image quality was limited by the camera spatial resolution (0.2mm) and sensitivity to scintillation light. The spot proton beam tracking was limited by the frame acquisition time of 30 frames per second. Additional limitations of this detector system included light attenuation within the scintillator slabs and reduced camera sensitivity to blue scintillation light
Conclusion
This plastic scintillator system demonstrated a novel detector that has large-volume and high spatial resolution for proton radiography. Moreover, this detector has the potential for proton CT-imaging through acquisition of proton projections from multiple views that can be used for 3D-image reconstruction. This system represents a compact 3D-detector for on-board proton imaging that directly utilizes the therapeutic proton beam.