SU‐E‐T‐34: Time Series Analysis of Skin Reactions during Heck and Neck IMRT

Purpose: To quantitatively characterize the time sequence of skin erythema in head and neck patients undergoing intensity modulated radiation therapy (IMRT) treatments using optical reflectance spectroscopy. The overall goal is to identify patients who will develop extreme skin responses earlier than is possible by visual inspection alone. Methods: Ten (10) patients undergoing IMRT for the treatment of head and neck cancers were followed throughout the course of their intervention. Daily spectral skin reflectance measurements were made in order to track changes in the tissue optical properties. Weekly thermoluminescent detector (TLD) readings were performed in the measurement area to verify the dose calculated by the treatment planning system. Patients also completed a weekly questionnaire on factors that may have affected their skin reaction, and were visually inspected by a radiation oncologist.Results: The data were fit by a 2‐component principle component analysis (PCA) model. The preliminary results show that absorbed dose is the largest contributor to changes in the spectral reflectance and that those changes are seen primarily at wavelengths above 600 nm. Differences among patient skin responses were seen and accounted for in the model Conclusions: The PCA model indicates that it may be possible to predict a patientˈs spectral skin reflectance measurement on the final day of treatment given an initial spectrum and the dose. Therefore, further analysis of the data may yield a method of determining patient reactions before visible signs are detected. Partial funding through Varian, Inc. and the Natural Sciences and Engineering Research Council of Canada.