Purpose: Total Skin Electron Therapy (TSET) uses large overlapping dual-fields and six patient postures to treat the entire skin surface. Cherenkov photons are emitted from interactions between the high energy electrons and tissue, thus allowing for visualization of the invisible radiation. Using spatial/geometrical information acquired from 3D meshes and Cherenkov images per patient posture, cumulative surface doses are obtained with the potential to evaluate uniformity on a per patient basis.
Methods: A structured light sensor is utilized to generate a 3D mesh of each patient in their treatment position, providing both anatomic and geometric information. Each patient is monitored during TSET via in-vivo detectors (IVD) and/or scintillating discs in nine locations. Cherenkov images are acquired for the 6 patient postures and are converted to dose distributions by applying a two-dimensional perspective geometry correction and a conversion factor from the IVD dose at the umbilicus. Cumulative dose on patient surface is obtained by back projecting the two-dimensional dose distribution onto an elliptical cylinder representing the patient anatomy. Rotational and positioning information for projection is determined from 3D meshes.
Results: Patients undergoing TSET in various conditions (whole body and half body) were imaged and analyzed, and the cumulative surface dose maps based on Cherenkov imaging have been evaluated for 9 patients. Agreement for the calculated cumulative dose compared to IVD measurements is shown for the chest location to be on average 2.4 Â± 10.2% and the umbilicus location to be on average 1.3 Â± 12.8%.
Conclusion: Our methodology allows for cumulative surface dose to be obtained for TSET patients. Future work includes further refinement of the elliptical cylinder to patient-specific body contour cylinder to more accurately represent the patient anatomy as determined from the 3D mesh object of the body, which will improve the accuracy and resolution of the calculated cumulative dose.