A novel Cherenkov radiation removal method for plastic scintillator detectors in a 0.35 T MR-Linac.

Purpose: This study evaluates methods for removing Cherenkov radiation (CR) from plastic scintillation detectors (PSDs), focusing on constraints specific to a 0.35 T MR-Linac system.

Methods: Five CR-removal methods were examined: cross calibration, fiber alone, multiloop, collimator rotation, and couch rotation. The first three (cross calibration, fiber alone, and multiloop) were tested on a 0.35 T MR-Linac (ViewRay Inc., USA) using the BluePhysics PSD (Blue Physics LLC, USA). These methods do not require collimator or couch rotation. The remaining two methods (collimator rotation and couch rotation) were tested on a Varian TrueBeam (Varian Medical Systems, USA) for comparison. Measurements were performed under various setup configurations, and Cherenkov radiation extraction (CRE) values were calculated to determine each method's effectiveness.

Results: The multiloop approach yielded a CRE of 0.7288, making it the most practical and robust for MR-Linac constraints because it requires neither collimator nor couch rotation. The cross calibration and fiber alone methods produced CRE values of 0.7318 and 0.7569, respectively. Collimator rotation gave 0.7255, comparable to multiloop. In contrast, couch rotation resulted in 0.7489 but exhibited more variability, suggesting lower reliability.

Conclusion: The multiloop method emerged as the most practical and robust technique for CR removal in 0.35 T MR-Linac systems. Its simplicity and compatibility with MR-Linac design constraints make it a highly effective approach for CR removal in PSD-based radiotherapy applications.