ESTRO 2023 - Abstract Book

S1402

Digital Posters

ESTRO 2023

Conclusion Although image quality was improved in ADMIRE_CBCT, the bone match with the reference pCT revealed a systematic difference of -0.93 mm in posterior-anterior direction compared to XVI_CBCT bone match. This systematic deviation can be clinically relevant when PTV margins of generally 5 mm are applied.

PO-1691 Segmentation on low resolution magnetic resonance images for prostate radiotherapy

S. Fransson 1 , R. Strand 2 , D. Tilly 1

1 Uppsala University Hospital, Medical Physics, Uppsala, Sweden; 2 Uppsala University, Information Technology, Uppsala, Sweden Purpose or Objective Real-time tracking on an MR-Linac requires 3D-segmentation with high temporal resolution as well as high spatial resolution. MR-imaging generally prohibits this in 3D and currently only 2D-acquisition is possible at such high temporal resolution and thereby the full information about the motion cannot be determined. In this work, we aim to solve this problem with high temporal resolution 3D-image acquisition by sacrificing the spatial resolution of the images. We then trained neural networks to obtain the high-resolution segmentations with these low-resolution images as input, thus investigating the performance of such segmentation approaches based on different levels of spatial resolution. Materials and Methods A total of 163 T2-weighted MR-scans of 26 prostate patients treated at our MR-Linac were included along with manual segmentations of CTV, bladder and rectum. The images were downsampled into three levels, reaching 1/2, 1/4 and 1/8 of the initial resolution in the phase-encoding directions while maintaining the resolution in the frequency encoding direction,