Chen Yazheng, Chen Xinfeng, Hall William, Prior Phil, Zhang Ying, Paulson Eric, Lang Jinyi, Erickson Beth, Li X Allen
Department of Radiation Oncology, Medical College of Wisconsin, Milwaukee, WI, USA.
Sichuan Cancer Hospital & Institute, Radiation Oncology Key Laboratory Of Sichuan Province, Chengdu, China.
Phys Imaging Radiat Oncol. 2019 Nov 20;12:22-29. doi: 10.1016/j.phro.2019.11.001. eCollection 2019 Oct.
In radiotherapy (RT) for pancreatic cancer, the dose to adjacent organs-at-risk (OAR) often limits the delivery of curative dose. This work aimed to find a body decubitus position that would lead to increased separation between the duodenum and pancreatic head.
Abdominal magnetic resonance images (MRI) of 11 healthy volunteers were acquired using a 1.5T MR-Linac for supine, left decubitus and right decubitus body positions. The geometry changes between different body positions were measured using Hausdorff Distance (HD) and overlap volume. RT plans were created on the MRIs. Commonly used dose-volume parameters (DVP), e.g., V - volume received at least 40 Gy, for OARs were compared for the three body positions.
The average of maximum HD between the duodenum and pancreatic head for all the cases was 4.0 ± 3.1 mm for supine, 7.3 ± 4.4 mm for left and 3.3 ± 1.4 mm for right positions (P < 0.01). The DVPs of the duodenum (e.g., V, V) for the left position were lower than those for the supine and right positions ( < 0.01). The right decubitus led to the highest duodenum DVPs. On average, the highest dose escalation was increased from 69 ± 4 Gy to 74 ± 5 Gy ( = 0.002) if body position was changed from supine to left decubitus.
The left decubitus increased the separation between duodenum and pancreas head, improving OAR sparing in RT for pancreatic cancer and allowing safer dose escalations to the tumor. The left decubitus positioning with proper immobilization could be adopted for MRI-guided adaptive RT.
在胰腺癌的放射治疗（RT）中，邻近危及器官（OAR）的剂量常常限制了根治性剂量的给予。本研究旨在找到一种体位，使十二指肠与胰头之间的间距增加。
使用1.5T MR直线加速器对11名健康志愿者进行仰卧位、左侧卧位和右侧卧位的腹部磁共振成像（MRI）。使用豪斯多夫距离（HD）和重叠体积测量不同体位之间的几何变化。在MRI上创建放疗计划。比较三种体位下常用的危及器官剂量体积参数（DVP），例如至少接受40 Gy的V体积。
所有病例中，仰卧位时十二指肠与胰头之间的最大HD平均值为4.0±3.1 mm，左侧卧位为7.3±4.4 mm，右侧卧位为3.3±1.4 mm（P<0.01）。左侧卧位时十二指肠的DVP（如V、V）低于仰卧位和右侧卧位（<0.01）。右侧卧位导致十二指肠DVP最高。平均而言，如果体位从仰卧位改为左侧卧位，最高剂量提升从69±4 Gy增加到74±5 Gy（=0.002）。
左侧卧位增加了十二指肠与胰头之间的间距，改善了胰腺癌放疗中对危及器官的保护，并允许更安全地增加肿瘤剂量。左侧卧位联合适当的固定可用于MRI引导的自适应放疗。
