Tumor Trailing for Liver SBRT on the MR-Linac
Tumor Trailing for Liver SBRT on the MR-Linac
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DOI：
10.1016/j.ijrobp.2018.09.011
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发表时间：
2019-02-01
影响因子：
7
通讯作者：
Sonke, Jan-Jakob
中科院分区：
文献类型：
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作者：
Fast, Martin;van de Schoot, Agustinus;Sonke, Jan-Jakob
目的：肿瘤拖尾是一种治疗递送技术，其根据目标的最后可用的时间平均位置连续地调整射束孔径。本研究调查是否肿瘤尾随磁共振（MR）直线加速器（直线加速器）可以提高目标覆盖率在肝脏立体定向体放射治疗（SBRT）的情况下，基线motion.Methods和材料：对于17例寡转移性肝病，中位SBRT治疗计划（3 × 20戈伊，11束调强放疗）创建的Elekta Unity MR直线加速器。使用内部开发的递送模拟器模拟治疗。将呼吸运动建模为周期性运动（患者特定幅度，4秒周期）和以下基线运动场景的叠加：连续线性漂移（0.5 mm/min），（2）治疗中途的单次移位（10 mm），（3）周期性漂移（幅度：5 mm，周期：5分钟）或（4）MR成像测量的基线漂移。在充分考虑患者和机器运动相互作用的情况下计算输送剂量。此外，拖尾实验验证的MR直线加速器使用可编程的运动phantom.Results：平均模拟交付和束上的时间分别为15.9和8.7分钟。>= 1 Hz的成像频率被认为是拖尾所必需的。与常规递送相比，拖尾使中位总肿瘤体积D98%剂量增加了1.9戈伊（线性漂移）、1.2戈伊（单次漂移）、0.7戈伊（周期性漂移）和0.5至1.5戈伊（测量漂移）/分次。在体模实验中，使用拖尾时，3%/2 mm局部伽马通过率几乎翻了一番，达到98%。结论：在所示患者队列基线运动的情况下，MR-Linac上的肿瘤拖尾恢复了肝脏SBRT中的目标剂量。(C)2018爱思唯尔公司All rights reserved.
Purpose: Tumor trailing is a treatment delivery technique that continuously adjusts the beam aperture according to the last available time-averaged position of the target. This study investigates whether tumor trailing on a magnetic resonance (MR) linear accelerator (linac) can improve target coverage in liver stereotactic body radiation therapy (SBRT) in the case of baseline motion.Methods and Materials: For 17 patients with oligometastatic liver disease, midposition SBRT treatment plans (3 x 20 Gy, 11-beam intensity modulated radiotherapy) were created for the Elekta Unity MR-Linac. Treatment was simulated using an in-house-developed delivery emulator. Respiratory motion was modelled as the superposition of periodic motion (patient-specific amplitude, 4-second period) and the following baseline motion scenarios: a continuous linear drift (0.5 mm/min), (2) a single shift halfway through treatment (10 mm), (3) a periodic drift (amplitude: 5 mm, period: 5 minutes), or (4) MR imaging-measured baseline drifts. Delivered dose was calculated under full consideration of the patient and machine motion interplay. In addition, trailing was experimentally validated on the MR-Linac using a programmable motion phantom.Results: The average simulated delivery and beam-on times were 15.9 and 8.7 minutes, respectively. An imaging frequency of >= 1 Hz was deemed necessary for trailing. Trailing increased the median gross tumor volume D98% dose by 1.9 Gy (linear drift), 1.2 Gy (single shift), 0.7 Gy (periodic drift), and 0.5 to 1.5 Gy (measured drifts) per fraction, compared with a conventional delivery. In the phantom experiments, the 3%/2 mm local gamma pass rate nearly doubled to 98% when using trailing.Conclusion: Tumor trailing on the MR-Linac restores target dose in liver SBRT in the case of baseline motion for the presented patient cohort. (C) 2018 Elsevier Inc. All rights reserved.