与其他癌症相比，胰腺癌的治疗结果较差。使用大分割立体定向放射治疗（SBRT）治疗胰腺癌已经实现了较高的局部控制率。实施立体定向放射治疗 (SBRT) 的挑战包括多个危及器官 (OAR) 的近距离以及目标体积分次间和分次内的位置变化。磁共振图像 (MRI) 引导放射治疗已显示出在线自适应放射治疗胰腺癌的潜力，与 CT 相比，其软组织对比度更佳。本研究的目的是调查胰腺癌不同治疗方法的靶区和 OAR 体积的变异性，并评估利用治疗日 MRI 进行治疗计划的适用性。在 5 天的时间里，每天使用西门子 Skyra 3 T MRI 扫描仪对 10 名健康志愿者进行两次扫描（间隔约 3 小时），以模拟 SBRT 日常模拟扫描以制定治疗计划。还进行了治疗前扫描以模拟患者设置和治疗。每次治疗时都会进行 4D MRI 扫描，以生成和评估内部目标体积 (ITV)。对于每个志愿者，在 Raystation 治疗计划系统 (TPS) 中按照第一天第一会话数据集 (D1S1) 的部门协议生成治疗计划，并应用体积密度覆盖来实现剂量计算。该治疗计划通过其他成像会议传播，并计算剂量。每天 (S1) 的每个第一个疗程都会生成一个额外的治疗计划，以模拟每日重新计划过程，并将该计划传播到当天的第二个疗程。通过 PTV 和 OAR 体积的 DVH 比较，根据原始治疗计划评估这些累积的模拟治疗剂量。与第一会话ITV和每日ITV相比，生成的ITV显示出较大的变化，平均幅度分别为22.44%±13.28%和25.83%±37.48%。对于所考虑的两个计划比较，PTV D95 减少了约 23.3%。周围OAR的剂量变化较大，小肠V30与D1S1计划相比增加了128.87%，与每日S1计划相比增加了43.11%。在缺乏额外运动管理和肿瘤跟踪技术的情况下，需要每日在线自适应放射治疗才能准确地治疗胰腺癌剂量。© 2023。Crown。

Pancreatic Cancer is associated with poor treatment outcomes compared to other cancers. High local control rates have been achieved by using hypofractionated stereotactic body radiotherapy (SBRT) to treat pancreatic cancer. Challenges in delivering SBRT include close proximity of several organs at risk (OARs) and target volume inter and intra fraction positional variations. Magnetic resonance image (MRI) guided radiotherapy has shown potential for online adaptive radiotherapy for pancreatic cancer, with superior soft tissue contrast compared to CT. The aim of this study was to investigate the variability of target and OAR volumes for different treatment approaches for pancreatic cancer, and to assess the suitability of utilizing a treatment-day MRI for treatment planning purposes. Ten healthy volunteers were scanned on a Siemens Skyra 3 T MRI scanner over two sessions (approximately 3 h apart), per day over 5 days to simulate an SBRT daily simulation scan for treatment planning. A pretreatment scan was also done to simulate patient setup and treatment. A 4D MRI scan was taken at each session for internal target volume (ITV) generation and assessment. For each volunteer a treatment plan was generated in the Raystation treatment planning system (TPS) following departmental protocols on the day one, first session dataset (D1S1), with bulk density overrides applied to enable dose calculation. This treatment plan was propagated through other imaging sessions, and the dose calculated. An additional treatment plan was generated on each first session of each day (S1) to simulate a daily replan process, with this plan propagated to the second session of the day. These accumulated mock treatment doses were assessed against the original treatment plan through DVH comparison of the PTV and OAR volumes. The generated ITV showed large variations when compared to both the first session ITV and daily ITV, with an average magnitude of 22.44% ± 13.28% and 25.83% ± 37.48% respectively. The PTV D95 was reduced by approximately 23.3% for both plan comparisons considered. Surrounding OARs had large variations in dose, with the small bowel V30 increasing by 128.87% when compared to the D1S1 plan, and 43.11% when compared to each daily S1 plan. Daily online adaptive radiotherapy is required for accurate dose delivery for pancreas cancer in the absence of additional motion management and tumour tracking techniques.© 2023. Crown.