Abstract：
(1) Background: To assess dosimetry benefits of stereotactic magnetic resonance (MR)-guided online adaptive radiotherapy (SMART) of liver metastases. (2) Methods: This is a subgroup analysis of an ongoing prospective registry including patients with liver metastases. Patients were treated at the MRIdian Linac between February 2020 and April 2022. The baseline plan was recalculated based on the updated anatomy of the day to generate the predicted plan. This predicted plan could then be re-optimized to create an adapted plan. (3) Results: Twenty-three patients received 30 SMART treatment series of in total 36 liver metastases. Most common primary tumors were colorectal- and pancreatic carcinoma (26.1% respectively). Most frequent fractionation scheme (46.6%) was 50 Gy in five fractions. The adapted plan was significantly superior compared to the predicted plan in regard to planning-target-volume (PTV) coverage, PTV overdosing, and organs-at-risk (OAR) dose constraints violations (91.5 vs. 38.0%, 6 vs. 19% and 0.6 vs. 10.0%; each p < 0.001). Plan adaptation significantly increased median BEDD95 by 3.2 Gy (p < 0.001). Mean total duration of SMART was 72.4 min. (4) Conclusions: SMART offers individualized ablative irradiation of liver metastases tailored to the daily anatomy with significant superior tumor coverage and improved sparing of OAR.
摘要：
（1）背景：评估肝脏转移瘤的立体定向磁共振（MR）引导的在线自适应放疗（SMART）的剂量学益处。（2）方法：这是一项正在进行的前瞻性注册的亚组分析，包括肝转移患者。患者在2020年2月至2022年4月期间在MRIdianLinac接受治疗。基于当天更新的解剖结构重新计算基线计划以生成预测计划。然后可以重新优化该预测的计划以创建适应的计划。（3）结果：23例患者接受了30个SMART治疗系列，共36个肝转移。最常见的原发性肿瘤是结肠直肠癌和胰腺癌（分别为26.1％）。最常见的分馏方案（46.6％）在五个馏分中为50Gy。在计划目标容量（PTV）覆盖范围方面，适应计划与预测计划相比明显优于预期计划，PTV过量,和危险器官(OAR)剂量限制违规(91.5vs.38.0%,6vs.19%和0.6vs.10.0%；每个p<0.001）。计划适应显着增加中位数BEDD953.2Gy（p<0.001）。SMART的平均总持续时间为72.4分钟。（4）结论：SMART提供针对日常解剖结构的肝转移瘤的个性化消融照射，具有明显的优越的肿瘤覆盖率和改善的OAR保留。
