Kensen Chavelli M, Betgen Anja, Wiersema Lisa, Peters Femke P, Kayembe Mutamba T, Marijnen Corrie A M, van der Heide Uulke A, Janssen Tomas M
Department of Radiation Oncology, The Netherlands Cancer Institute, 1066 CX Amsterdam, The Netherlands.
Department of Scientific Administration, The Netherlands Cancer Institute, 1066 CX Amsterdam, The Netherlands.
Cancers (Basel). 2023 Feb 5;15(4):1009. doi: 10.3390/cancers15041009.
The purpose of this study was to characterize the motion and define the required treatment margins of the pathological mesorectal lymph nodes (GTV) for two online adaptive MRI-guided strategies for sequential boosting. Secondly, we determine the margins required for the primary gross tumor volume (GTV). Twenty-eight patients treated on a 1.5T MR-Linac were included in the study. On T2-weighted images for adaptation (MRI) before and verification after irradiation (MRI) of five treatment fractions per patient, the GTV and GTV were delineated. With online adaptive MRI-guided radiotherapy, daily plan adaptation can be performed through the use of two different strategies. In an adapt-to-shape (ATS) workflow the interfraction motion is effectively corrected by redelineation and the only relevant motion is intrafraction motion, while in an adapt-to-position (ATP) workflow the margin (for GTV) is dominated by interfraction motion. The margin required for GTV will be identical to the ATS workflow, assuming each fraction would be perfectly matched on GTV. The intrafraction motion was calculated between MRI and MRI for the GTV and GTV separately. The interfraction motion of the GTV was calculated with respect to the position of GTV, assuming each fraction would be perfectly matched on GTV. PTV margins were calculated for each strategy using the Van Herk recipe. For GTV we randomly sampled the original dataset 20 times, with each subset containing a single randomly selected lymph node for each patient. The resulting margins for ATS ranged between 3 and 4 mm (LR), 3 and 5 mm (CC) and 5 and 6 mm (AP) based on the 20 randomly sampled datasets for GTV. For ATP, the margins for GTV were 10-12 mm in LR and AP and 16-19 mm in CC. The margins for ATS for GTV were 1.7 mm (LR), 4.7 mm (CC) and 3.2 mm anterior and 5.6 mm posterior. Daily delineation using ATS of both target volumes results in the smallest margins and is therefore recommended for safe dose escalation to the primary tumor and lymph nodes.
本研究的目的是描述两种在线自适应MRI引导的序贯增敏策略中病理性直肠系膜淋巴结（GTV）的运动情况，并确定所需的治疗边界。其次，我们确定原发性大体肿瘤体积（GTV）所需的边界。本研究纳入了28例在1.5T MR直线加速器上接受治疗的患者。在每位患者每5个治疗分次的照射前适应（MRI）和照射后验证（MRI）的T2加权图像上，勾勒出GTV和GTV。通过在线自适应MRI引导放疗，可通过两种不同策略进行每日计划调整。在适应形状（ATS）工作流程中，通过重新勾勒有效校正分次间运动，唯一相关的运动是分次内运动，而在适应位置（ATP）工作流程中，（GTV的）边界主要由分次间运动决定。假设每个分次在GTV上完美匹配，GTV所需的边界将与ATS工作流程相同。分别计算GTV和GTV在MRI和MRI之间的分次内运动。相对于GTV的位置计算GTV的分次间运动，假设每个分次在GTV上完美匹配。使用范·赫克公式为每种策略计算PTV边界。对于GTV，我们对原始数据集进行了20次随机抽样，每个子集包含每位患者单个随机选择的淋巴结。基于GTV的20个随机抽样数据集，ATS产生的边界在左右方向（LR）为3至4毫米、头脚方向（CC）为3至5毫米、前后方向（AP）为5至6毫米。对于ATP，GTV在LR和AP方向的边界为10 - 12毫米，在CC方向为16 - 19毫米。GTV的ATS边界在LR方向为1.7毫米、CC方向为4.7毫米、前方为3.
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