Author: Haonian Gong, Yue Gu, Meiqi Liu, Hsiao-Ming Lu, Yuxiang Wang, Yidong Yang 👨🔬
Affiliation: Hefei Ion Medical Center, The First Affiliated Hospital of USTC, Division of Life Sciences and Medicine, University of Science and Technology of China, Department of Engineering and Applied Physics, University of Science and Technology of China 🌍
Purpose: To develop a proton CT system using scintillator-based 2D dose distribution detection for accurate proton imaging.
Methods: The proposed proton CT system consists of a brass collimator with a 50 mm × 1 mm slit for proton beam reshaping, an object stage capable of horizontal translation (perpendicular to the proton beam path) and 360° rotation, a plastic scintillator for dose-to-light conversion, and a scientific complementary metal oxide semiconductor (sCMOS) camera to acquire 2D lateral light distributions. A calibration procedure was performed to convert the obtained 2D light distribution into 2D dose distribution. To derive proton ranges, an algorithm was developed that modeled each 2D dose distribution as a sum of contributions from proton beamlets. The water equivalent path length (WEPL) of the imaged object was calculated as the difference between proton ranges with and without the object in the beam path. The relative stopping power (RSP) map was reconstructed from WEPLs using the filtered back projection (FBP) algorithm. To validate the imaging performance, proton CT imaging was performed on a custom-designed acrylic phantom containing four cylindrical inserts of air, Teflon, polyethylene and Delrin and the accuracy of the reconstructed RSP map was evaluated.
Results: The proposed algorithm accurately extracted proton beam ranges from the 2D dose distributions. Proton CT imaging achieved decent RSP reconstruction accuracy, with RSP errors of 0.37%, 1.62%, 0.98%, and 0.69% for acrylic, Teflon, polyethylene, and Delrin, respectively.
Conclusion:
The proposed proton CT system demonstrated high accuracy in RSP reconstruction. This system holds potential in directly acquisition of proton RSP for preclinical and clinical proton dose calculation.