ESTRO 2024 - Abstract Book

S4164

Physics - Intra-fraction motion management and real-time adaptive radiotherapy

ESTRO 2024

Fig. 2 shows a map of the TIV over the 100 frames, before (2A) and after (2B) registration. Due to registration the TIV marked lower especially in the bowel wall. The bowel contents showed relatively higher TIV. The mean IC on the full bowel bag was 1.3 mm for two consecutive frames and 5.3 mm for the entire sequential registration from the first to the last frame, indicating that the IC increased due to the large number of registration steps.

Conclusion:

We optimized a combination of a fast MR acquisition with consecutive registration using the Cornelius-Kanade algorithm which allows for accurate small bowel tracking during MR-guided radiotherapy treatment of the pelvis. Here we showcase this pipeline and two associated validation methods in scans of a volunteer. At the moment the mean IC is still sensitive to bowel content motion, which explains the relatively high IC value in this example case. This is supported by the higher TIV inside the bowel, compared to the bowel wall. Next steps include improving the IC for high numbers of registration steps and focus its analysis only on the bowel wall and not its contents as the latter are not radiosensitive. Furthermore, the effectiveness of the pipeline will be investigated on a larger cohort of volunteers. We see applications of this work in toxicity research and dose tracking, where the latter might also be useful when moving to multi-isocenter treatments in the pelvis and/or abdomen.

Keywords: MR, Image-guided radiotherapy, bowel tracking

References:

[1] Olopade, F., Norman, A., Blake, P., Dearnaley, D., Harrington, K., Khoo, V. et al. (2005) A modified Inflammatory Bowel Disease questionnaire and the Vaizey Incontinence questionnaire are simple ways to identify patients with significant gastrointestinal symptoms after pelvic radiotherapy. Br J Cancer 92: 1663–1670. [2] Zachiu, C., Denis de Senneville, B., Willigenburg, T., Voort van Zyp, J. R. N., de Boer, J. C. J., Raaymakers, B. W., & Ries, M. (2020). Anatomically-adaptive multi-modal image registration for image-guided external-beam radiotherapy. Physics in medicine and biology, 65(21), 215028. https://doi.org/10.1088/1361-6560/abad7d