Speaker
Description
High-dose-rate (HDR) brachytherapy relies on the precise positioning of a radioactive source through applicators or needles to deliver conformal dose distributions to tumors while sparing adjacent healthy tissue. However, most conventional treatment planning systems do not explicitly model the dose contribution during the entire source transit phase, including entry into the body, movement between dwell positions, and return to the afterloader's safe position. This simplification may lead to underestimation of doses to tumour and organs at risk (OARs), particularly in anatomically complex or deeply situated treatment sites. Following the investigation of source motion in intraluminal esophageal brachytherapy, the current study broadens the scope to interstitial techniques and evaluates the impact of source speed and acceleration profiles across different commercial HDR afterloader systems. Using time-resolved (4D) Monte Carlo simulations implemented in TOPAS, realistic source trajectories were modelled to reflect clinical delivery conditions. Comparative dosimetric analysis was conducted to quantify the effects of system-specific transit behaviour on target and OAR doses. The results underscore the importance of incorporating source motion into dosimetric evaluations, as variations in device kinematics can significantly influence both therapeutic and unintended radiation exposures.
