A 1.5T MRI combined with a linear accelerator (Unity®, Elekta; Stockholm, Sweden) is a device that shows promise in MRI-guided stereotactic body radiation treatment (SBRT). Previous studies utilized the manufacturer’s pre-set MRI sequences (i.e., T2 Weighted (T2W)), which limited the visualization of pancreatic and intra-abdominal tumors and organs at risk (OAR). Here, a T1 Weighted (T1W) sequence was utilized to improve the visualization of tumors and OAR for online adapted-to-position (ATP) and adapted-to-shape (ATS) during MRI-guided SBRT. Twenty-six patients, 19 with pancreatic and 7 with intra-abdominal cancers, underwent CT and MRI simulations for SBRT planning before being treated with multi-fractionated MRI-guided SBRT. The boundary of tumors and OAR was more clearly seen on T1W image sets, resulting in fast and accurate contouring during online ATP/ATS planning. Plan quality in 26 patients was dependent on OAR proximity to the target tumor and achieved 96 ± 5% and 92 ± 9% in gross tumor volume D90%and planning target volume D90%. We utilized T1W imaging (about 120 s) to shorten imaging time by 67% compared to T2W imaging (about 360 s) and improve tumor visualization, minimizing target/OAR delineation uncertainty and the treatment margin for sparing OAR. The average time-consumption of MRI-guided SBRT for the first 21 patients was 55 ± 15 min for ATP and 79 ± 20 min for ATS.
1.5T磁共振成像联合直线加速器（Unity®，Elekta；瑞典斯德哥尔摩）是一种在磁共振引导立体定向放射治疗中展现出应用前景的设备。既往研究多采用制造商预设的磁共振序列（如T2加权成像），这限制了胰腺及腹腔内肿瘤与危及器官的可视化效果。本研究采用T1加权成像序列，以提升磁共振引导立体定向放射治疗中在线位置自适应与形状自适应过程中肿瘤及危及器官的可视化质量。26例患者（19例胰腺癌、7例腹腔内肿瘤）在接受分次磁共振引导立体定向放射治疗前，均完成CT与磁共振模拟定位以制定治疗计划。T1加权图像能更清晰地显示肿瘤与危及器官边界，从而实现在线位置自适应/形状自适应计划过程中快速精准的勾画。26例患者的计划质量取决于危及器官与靶肿瘤的邻近程度，大体肿瘤体积D90%与计划靶体积D90%分别达到96±5%和92±9%。相较于T2加权成像（约360秒），采用T1加权成像（约120秒）将扫描时间缩短67%，同时改善肿瘤可视化效果，最大程度减少靶区/危及器官勾画不确定性，并为保护危及器官缩小治疗边界。前21例患者磁共振引导立体定向放射治疗的平均耗时：位置自适应为55±15分钟，形状自适应为79±20分钟。
肿瘤(癌症)患者之家