ESTRO 2023 - Abstract Book

S1827

Digital Posters

ESTRO 2023

average DVH for PTV, bladder and rectum and distance-to-target dose histogram (DDH) for bladder rectum and normal tissue (excluding bladder and rectum) were calculated. To calculate DDH, distance-to-target was determined for each target volume voxel (i.e. normal tissue, rectum and bladder). Subsequently, dose values of each target volume voxel were signed to bin according to distance-to-target (width 1 mm). Finally, DDH was determined by calculating mean value for each bin. Statistical significance between the groups were determined using unpaired t-test. Level of statistical significance was set to p <0.05. Results Volume of PTV was found to be 6.9% larger in SO group as compared to those in VOLO group (Table 1). Average DVHs for PTV, bladder and rectum and DDHs for normal tissue, bladder and rectum are presented in Figure 1. Only minor differences were detected in D95% or D0.5cc between the SO and VOLO groups. Mean dose to rectum and bladder were reduced by 36.5% and 29.8% when comparing VOLO to SO plans (Table 1). Smaller differences (0.5-5.8%) where detected in D0.5cc and D2cc values between SO and VOLO groups. GI and CI were reduced by 6% and 3% respectively with VOLO optimizer. Table 1 . Mean and standard deviation (SD) calculated for DVH parameters.