Analysis of patient intra-fractional motion in free-breathing radiotherapy for breast cancer

Surface-guided radiotherapy (SGRT) is an innovative method for positioning and monitoring patients during treatment. This non-invasive technique relies on visible light to determine the real-time patient's surface position against the reference body surface. 
This study investigates the application of surface-guided radiotherapy (SGRT) for positioning and monitoring in breast cancer patients. Utilizing SGRT on a cohort of 366 patients, the research explores how inter-fraction errors, treatment time, and the number of fractions may impact intra-fraction accuracy. Patients were divided into well-setup and bad-setup groups based on the number of Cone Beam CTs (CBCTs) acquired during the treatment. Results indicate that patients with large inter-fraction errors exhibit more significant intra-fraction errors, with mean and maximum errors increasing with treatment time. The study also notes a slight correlation between intra-fraction error and the number of treatment fractions. 
Further investigations will be carried out to explore additional factors influencing intra-fraction errors, including immobilization systems and patient characteristics.