Motion management and response prediction for real-time adaptive MRI-guided RT in liver and rectal cancer

由于最佳的软组织对比度，在线自适应MR引导放射治疗在腹部区域具有很大的潜力，但是在该身体区域中，在会话之间和会话内（由于呼吸、蠕动和患者移动）的肿瘤和危险器官的位置变化很大，这是一个挑战。在第一个资助阶段，通过解决一些挑战，建立了肝脏和直肠肿瘤的新治疗概念，并在前瞻性临床方案中治疗和评估了50多名患者。在这些结果的基础上，在所请求的扩展中追求以下目标：MR-直线加速器即将进行的更新将在可选的呼吸阶段实现高剂量辐照，可能通过减少辐照体积来进一步优化治疗。在第一个工作包中，将在20例患者扩展的队列中，与之前的治疗策略相比，对新技术的可行性、治疗持续时间和剂量测定进行科学评价。此外，还将研究肝功能降低的患者是否可以使用新的治疗方法和功能成像用更高的辐射剂量进行治疗。第二个工作包涉及解剖结构的跟踪。在项目第一阶段开发和研究的自我监督跟踪方法将扩大到会议期间和会议之间的跟踪。研究了病变和器官跟踪对不同解剖区域（肝脏和直肠）和成像序列的可推广性。从而在在线自适应放射治疗的背景下自动化目标结构和危险器官的手动分割的非常耗时的部分。虽然早期直肠癌主要作为第一项目阶段剂量递增工作的基础进行检查，但局部晚期肿瘤现在将成为扩展阶段第三工作包的研究对象。由于这些肿瘤的大小通常不适合整个肿瘤的剂量递增，因此将研究是否可以使用扩散加权和灌注成像在这些肿瘤中识别出可能具有放射抗性并且应该用更高辐射剂量治疗的亚区。

Online adaptive MR-guided radiotherapy has great potential in the abdominal region due to the optimal soft tissue contrast, but the large positional variability of tumors and organs at risk in this body region between sessions and within a session (due to respiration, peristaltic and patient movement) presents a challenge. In the first funding phase, new therapeutic concepts for liver and rectal tumors were established by addressing some challenges, and over 50 patients were treated and evaluated within a prospective clinical protocol. Building on these results, the following objectives are pursued in the requested extension: An upcoming update of the MR-Linac will enable high-dose irradiation in a selectable breathing phase, potentially leading to further therapy optimization by reducing the irradiated volumes. In the first work package, the new technology will be scientifically evaluated with respect to feasibility, treatment duration, and dosimetry compared to the previous treatment strategy in a cohort expanded by 20 patients. Additionally, it will be investigated whether patients with reduced liver function can be treated with higher radiation doses using the new treatment method and functional imaging. The second work package deals with the tracking of anatomical structures. The self-supervised tracking method, developed and investigated in the first project phase, will be extended to intra- and inter-session tracking. The generalizability of the lesion and organ tracking towards different anatomical areas (liver and rectum) and imaging sequences is investigated. Thereby automating the very time-consuming part of manual segmentation of the target structures and organs at risk in the context of online adaptive radiotherapy. While early rectal carcinomas were mainly examined as the basis for the dose escalation work in the first project phase, locally advanced tumors will now be the subject of investigation in the third work package of the extension phase. Since these tumors are generally not suitable for dose escalation of the entire tumor due to their size, it will be investigated whether subareas can be identified in these tumors using diffusion-weighted and perfusion imaging that are potentially radioresistant and should be treated with higher radiation doses.