ESTRO 2021 Abstract Book

S654

ESTRO 2021

1). BRIGHT consists of a bi-objective planning model, in which the TP aims (Table 1) are grouped into one coverage objective and one sparing objective, referred to as the Least Coverage Index (LCI) and Least Sparing Index (LSI). These were constructed in a worst-case manner: For example, an LCI = 2.0% means that all targets are covered at least 2.0% more than their planning-aim. BRIGHT’s graphical user interface allows navigation over the coverage-sparing trade-off curve and allows to make a selection for further dose-calculation and clinical plan determination in Oncentra Brachy. For each patient the plan selecting aspects and process times were monitored (Table 1).

Results For all patients, multiple plans that satisfied all planning aims could be selected in BRIGHT. Table 1 summarizes the results of the monitored parameters, reached planning aims, and LCI/LSI of the resulting clinical treatment plan for each patient. Time was spent on manual optimization of the BRIGHT plan before clinical plan approval to reduce large dwell times that caused undesired large high-dose sub-volumes in the target. Parameters of influence on the clinical plan choice were: Patient-specific clinical information, knowledge of the trade-off curve, dwell time pattern, and isodose distribution. As example: Based on these parameters the focus in patient 4 was on sparing of the urethra due to urinary complaints and the decision was made to underdose the target. In patient 2 a catheter was found incorrectly reconstructed, after correction the plan was not re-optimized in BRIGHT due to time pressure, resulting in a higher prostate V100%.