ESTRO 2023 - Abstract Book

S651

Monday 15 May 2023

ESTRO 2023

Results The relative DVH parameters of the GTV, duodenum, small bowel and stomach are presented in fig. 2, with respect to the measured GTV respiratory amplitude and drift magnitude. The mean (SD) D99% of the GTV was 0.94 (0.06), and the mean (SD) D0.5cc of the duodenum, small bowel and stomach were respectively 0.98 (0.04), 1.00 (0.07) and 0.98 (0.06). Upon closer inspection of the fractions where the largest degradation in tumor coverage was measured, it was observed that significant lateral drifts (> 4 mm) had occurred during these fractions. The largest relative OAR dose increase of 122% in small bowel D0.5cc turned out to be a negligible absolute increase from 11.8 Gy to 14.3 Gy (scaled to the complete 40 Gy treatment regimen).

Conclusion We employed a fast, real-time 3D cine MRI sequence for dose reconstruction in the upper abdomen. In this study, we demonstrated that the motion fields, acquired directly from these images, can be used for dose warping. The reconstructed delivered dose showed only a modest degradation of tumor coverage, mostly attainable to baseline drifts. This emphasizes the need for motion monitoring and development of intrafraction treatment adaptation solutions, such as baseline drift corrections.

OC-0781 Histopathology-validated GTV delineations of intra-prostatic lesions with mpMRI and PSMA-PET