Commissioning a Plastic Scintillator Detector for Clinical Use In IGRT and Bgrt on a PET-Linac
Abstract
Purpose
To commission Standard Imaging Exradin W1 scintillator detector (W1) on RefleXIon PET-Linac system for small-field dosimetry in both image-guided radiotherapy (IGRT) and biology-guided radiotherapy (BgRT).
Methods
The W1 was first characterized on conventional C-arm Linacs to determine the Cerenkov Light Ratio (CLR). Then, it was recalibrated on the RefleXion PET-linac (6MV FFF beam, maximum clinical filed size 40x2 cm2). CLR measurements were performed in a water tank using parallel and perpendicular setup with a dedicated W1 holder. The gain factor of absolute dose calibration was established with the machine specific reference field (10×2 cm²), and W1-measured output factors were compared with commissioned data. Isocenter point doses for four IGRT plans were measured with W1 and compared to the planned dose. Detector performance under PET imaging conditions was further evaluated by measuring W1 response without beam delivery in the presence of a Ge-68 point source. Finally, point-dose measurement was performed for a BgRT plan using a Ge-68 source to mimic a tracer-avid target, and W1 measured dose was compared to planned dose.
Results
W1 demonstrated stable CLR correction (0.698) and linear dose response (gain factor of 2.29) for both measurement setups. The output factors agreed with the commissioned clinical data. Point-dose measurements for four IGRT and BgRT showed good agreement with planned dose and ion chamber measurements (<3%). Point-dose measurement of BgRT also showed good agreement with planned dose (2.4%), though minor signal interference was observed during PET acquisition.
Conclusion
W1 detector is compatible with PET imaging and BgRT delivery on a PET-linac, enabling accurate dosimetry without PET-induced signal perturbation. We successfully commissioned W1 plastic scintillator for PET-Linac system. These results support its clinical use for in-vivo dosimetric verification of smaller tumor (<2cm) in integrated IGRT and PET-based BgRT delivery, where dosimetric assessment remains challenging with current available detectors.