Author: Baozhu Lu, Hongjing Sun, Timothy C. Zhu, Yifeng Zhu 👨🔬
Affiliation: University of Pennsylvania 🌍
Purpose: This study aims to validate the feasibility of using Cherenkov imaging for surface dose distribution measurement during Total Skin Electron Therapy (TSET) by developing a perspective-corrected measurement system and characterizing its performance against conventional optical stimulated luminescent dosimeters (OSLD) and scintillator luminescent dosimeters (SLD), with the goal of providing comprehensive dose distribution verification for improving treatment quality assurance.
Methods: A time-gated intensified camera system was used to capture Cherenkov signals during TSET delivery (6 MeV electrons, SSD=500cm). The system was calibrated using a flat PVC board with OSLDs at different vertical positions. Perspective correction factors were derived to account for camera vignetting effects and geometric dependencies. Images were recorded during treatment for multiple patients across six standard treatment positions, with subsequent analysis comparing dose distributions at key anatomical points using both Cherenkov imaging and conventional dosimeters.
Results: Initial analysis from our preliminary cohort showed that Cherenkov imaging correlates well with OSLD measurements at several anatomical sites, particularly the chest (0.93±0.11) and right hand (0.71±0.11) relative to umbilicus. SLD measurements demonstrated a linear relationship with dose (Dose=0.0003548×SL, R²>0.99) in phantom studies, but showed significant orientation dependence in patient measurements, with variations up to 49% compared to OSLD readings. The study is being expanded to include an additional cohort of patients (target N=50) to validate these findings and establish more robust correction factors across different treatment positions and anatomical sites.
Conclusion: Preliminary results suggest that Cherenkov imaging with geometric corrections can provide valuable dose distribution analysis in TSET. While SLD shows promising linearity in controlled conditions, its clinical application requires further investigation of geometric dependencies. Ongoing data collection from additional patients will help establish more comprehensive correction factors and validate the reliability of these complementary measurement approaches for treatment verification.