Towards fast online intrafraction replanning for free-breathing stereotactic body radiation therapy with the MR-linac
Towards fast online intrafraction replanning for free-breathing stereotactic body radiation therapy with the MR-linac
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DOI：
10.1088/1361-6560/aa82ae
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发表时间：
2017-09-21
影响因子：
3.5
通讯作者：
Raaymakers, B. W.
中科院分区：
文献类型：
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作者：
Kontaxis, C.;Bol, G. H.;Raaymakers, B. W.
在UMC Utrecht（荷兰乌得勒支）安装的混合MRI-放射治疗机，如MR直线加速器（Elekta AB，斯德哥尔摩，瑞典），将能够在治疗期间提供实时患者成像。为了利用系统的能力，并使在线自适应治疗，新一代的软件应开发，从运动估计到治疗计划的适应。在这项工作中，我们提出了一个原则的证明自适应管道设计的高精度立体定向体放射治疗（SBRT）适用于受呼吸运动，如肾细胞癌（RCC）的网站。我们利用我们的研究MRL治疗计划系统（MRLTP），模拟一个单一的部分25戈伊自由呼吸SBRT治疗肾细胞癌进行束间重新规划为两名患者和一名志愿者。模拟管道包括（预射束）4D-MRI和（在线）2D电影-MR采集的组合。4DMRI用于生成中间位置参考体积，而电影MRI通过内部运动模型提供三维（3D）可变形矢量场（DVF），描述治疗期间的解剖变化。在治疗部分期间，在射束间间隔，更新患者的中间位置体积，并根据模型计算的基础运动准确重建输送剂量。然后使用MRLTP模拟快速在线重新计划，瞄准最新解剖结构并结合先前输送的剂量。将自适应治疗与传统的中间位置SBRT计划进行比较，该计划具有在相同运动轨迹上重建的3 mm计划靶体积边缘。我们证明了我们的系统产生了更紧密的剂量分布，从而使健康组织幸免于难，同时向目标提供更多的剂量。管道能够解释治疗期间发生的基线变化/漂移，确保治疗部分结束时的目标覆盖率。
The hybrid MRI-radiotherapy machines, like the MR-linac (Elekta AB, Stockholm, Sweden) installed at the UMC Utrecht (Utrecht, The Netherlands), will be able to provide real-time patient imaging during treatment. In order to take advantage of the system's capabilities and enable online adaptive treatments, a new generation of software should be developed, ranging from motion estimation to treatment plan adaptation. In this work we present a proof of principle adaptive pipeline designed for high precision stereotactic body radiation therapy (SBRT) suitable for sites affected by respiratory motion, like renal cell carcinoma (RCC). We utilized our research MRL treatment planning system (MRLTP) to simulate a single fraction 25 Gy free-breathing SBRT treatment for RCC by performing inter-beam replanning for two patients and one volunteer. The simulated pipeline included a combination of (prebeam) 4D-MRI and (online) 2D cine-MR acquisitions. The 4DMRI was used to generate the mid-position reference volume, while the cine-MRI, via an in-house motion model, provided three-dimensional (3D) deformable vector fields (DVFs) describing the anatomical changes during treatment. During the treatment fraction, at an inter-beam interval, the mid-position volume of the patient was updated and the delivered dose was accurately reconstructed on the underlying motion calculated by the model. Fast online replanning, targeting the latest anatomy and incorporating the previously delivered dose was then simulated with MRLTP. The adaptive treatment was compared to a conventional mid-position SBRT plan with a 3 mm planning target volume margin reconstructed on the same motion trace. We demonstrate that our system produced tighter dose distributions and thus spared the healthy tissue, while delivering more dose to the target. The pipeline was able to account for baseline variations/drifts that occurred during treatment ensuring target coverage at the end of the treatment fraction.