"MR-based contour propagation for rectal cancer patients"
Sander Uilkema, Uulke A. van der Heide, Jan-Jakob Sonke, Marius Staring and Jasper Nijkamp
In rectal cancer patients large day-to-day target volume deformations occur, leading to large PTV margins. The introduction of MR-guided RT with excellent soft-tissue contrast, facilitates adaptive procedures, like online re-planning with smaller margins. Time constraints demand for automatic contouring of the daily-MR. A possible fast solution is contour propagation with deformable image-registration (DIR). In rectal cancer patients DIR is challenging because of large local deformations of the CTV (meso-rectum) caused by (dis)appearing rectal and bladder content. To deal with this challenge, pre-treatment delineations can be used to define a region-of-interest (ROI) to limit DIR to the part of the anatomy, and also allows excluding regions with (dis-)appearing content. In this study, we investigate optimal parameter settings of MR-to-MR DIR, in the context of contour-propagation of the meso-rectum.