Exhibit Hall | Forum 4
Purpose: Cherenkov imaging is being applied to TSET as a non-invasive and real-time remote monitoring technique. Using Monte Carlo (MC) simulation with realistic patient geometries, this study aims to verify both dose and Cherenkov light distributions on patient skin and provides Cherenkov-to-dose conversion mapping, which is the key to obtaining delivered skin dose distributions from Cherenkov images.
Methods: An MC simulation package with TOPAS is developed for TSET with the Stanford technique. After validation with measurements of liquid and solid water phantoms at different SSDs, a detailed MC study has been applied to a standing PVC board in the position of TSET patients to verify the relationship between dose and Cherenkov distributions by comparing MC results against measurements. After that, for each posture of each patient, a 3D dose distribution and a 2D Cherenkov image are obtained via MC simulation with the input of CT DICOM patient geometry.
Results: Measurements of the PVC board show that Cherenkov distribution deviates from the uniformity of dose along the vertical direction in dual fields. MC simulation indicates that the source of the deviation is the spoiler. After removing the spoiler in the clinic, measurements of dose and Cherenkov images have consistent vertical distributions. Similarly, Cherenkov light from patients shows less uniformity along the vertical direction comparing with dose from in-vivo OSLD measurements. MC simulation with realistic patient geometries verifies the differences between dose and Cherenkov distributions and provides 2D/3D Cherenkov-to-dose conversion factors.
Conclusion: MC simulation helped to identify that the spoiler is the major source of deviations between Cherenkov and dose distributions. MC simulation also indicates that the cumulative dose non-uniformity in OSLD measurements is due to variations of SSDs of different parts of patient bodies, and the patient orientations. MC simulation output can be used to generate patient-specific Cherenkov-to-dose conversion factors.
Funding Support, Disclosures, and Conflict of Interest: NIH R21CA239127