ESTRO 2025 - Abstract Book

S333

Brachytherapy - Physics

ESTRO 2025

The two image sets were registered (Figure 1), and the OARs—small bowel loops, rectum, and bladder—were analyzed using MIM Encore ® software to obtain volumetric values and DICE coefficients as an overlap metric. A paired t-test was conducted to evaluate volumetric differences.

Results:

Results showed that volumetric variations in OARs (small bowel loops, rectum, and bladder) between intra-daily fractions, taken six hours apart, were statistically insignificant, with high p-values (>0.05) (Figure 2). Image registration demonstrated accurate OAR overlap with DICE coefficients exceeding 0.7: 0.817 for small bowel loops, 0.844 for the rectum, and 0.9 for the bladder. Small bowel loops exhibited greater spatial variability due to their inherent mobility, while the bladder showed near-complete overlap even after six hours.