Schlosser Jeffrey, Gong Ren Hui, Bruder Ralf, Schweikard Achim, Jang Sungjune, Henrie John, Kamaya Aya, Koong Albert, Chang Daniel T, Hristov Dimitre
SoniTrack Systems Inc., Palo Alto, California 94304.
Department of Radiation Oncology, School of Medicine, Stanford University, Stanford, California 94305.
Med Phys. 2016 Nov;43(11):5951. doi: 10.1118/1.4964454.
To present a system for robotic 4D ultrasound (US) imaging concurrent with radiotherapy beam delivery and estimate the proportion of liver stereotactic ablative body radiotherapy (SABR) cases in which robotic US image guidance can be deployed without interfering with clinically used VMAT beam configurations.
The image guidance hardware comprises a 4D US machine, an optical tracking system for measuring US probe pose, and a custom-designed robot for acquiring hands-free US volumes. In software, a simulation environment incorporating the LINAC, couch, planning CT, and robotic US guidance hardware was developed. Placement of the robotic US hardware was guided by a target visibility map rendered on the CT surface by using the planning CT to simulate US propagation. The visibility map was validated in a prostate phantom and evaluated in patients by capturing live US from imaging positions suggested by the visibility map. In 20 liver SABR patients treated with VMAT, the simulation environment was used to virtually place the robotic hardware and US probe. Imaging targets were either planning target volumes (PTVs, range 5.9-679.5 ml) or gross tumor volumes (GTVs, range 0.9-343.4 ml). Presence or absence of mechanical interference with LINAC, couch, and patient body as well as interferences with treated beams was recorded.
For PTV targets, robotic US guidance without mechanical interference was possible in 80% of the cases and guidance without beam interference was possible in 60% of the cases. For the smaller GTV targets, these proportions were 95% and 85%, respectively. GTV size (1/20), elongated shape (1/20), and depth (1/20) were the main factors limiting the availability of noninterfering imaging positions. The robotic US imaging system was deployed in two liver SABR patients during CT simulation with successful acquisition of 4D US sequences in different imaging positions.
This study indicates that for VMAT liver SABR, robotic US imaging of a relevant internal target may be possible in 85% of the cases while using treatment plans currently deployed in the clinic. With beam replanning to account for the presence of robotic US guidance, intrafractional US may be an option for 95% of the liver SABR cases.
介绍一种用于在放射治疗束传输过程中同步进行机器人四维超声（US）成像的系统，并估计在不干扰临床使用的容积调强弧形放疗（VMAT）束配置的情况下，可部署机器人US图像引导的肝脏立体定向消融体部放射治疗（SABR）病例的比例。
图像引导硬件包括一台四维US机器、一个用于测量US探头姿态的光学跟踪系统，以及一个用于获取免手持US容积的定制设计机器人。在软件方面，开发了一个包含直线加速器、治疗床、计划CT和机器人US引导硬件的模拟环境。通过使用计划CT模拟US传播，在CT表面渲染目标可见性图，以指导机器人US硬件的放置。该可见性图在前列腺模型中得到验证，并通过从可见性图建议的成像位置捕获实时US在患者中进行评估。在20例接受VMAT治疗的肝脏SABR患者中，使用模拟环境虚拟放置机器人硬件和US探头。成像目标为计划靶体积（PTV，范围5.9 - 679.5 ml）或大体肿瘤体积（GTV，范围0.9 - 34ml）。记录与直线加速器、治疗床和患者身体的机械干扰情况以及与治疗束的干扰情况。
对于PTV目标，80%的病例可以进行无机械干扰的机器人US引导，60%的病例可以进行无束干扰的引导。对于较小的GTV目标，这些比例分别为95%和85%。GTV大小（1/20）、细长形状（1/20）和深度（1/20）是限制无干扰成像位置可用性的主要因素。在两名肝脏SABR患者的CT模拟过程中部署了机器人US成像系统，并成功在不同成像位置采集了四维US序列。
本研究表明，对于VMAT肝脏SABR，在使用当前临床部署的治疗计划时，85%的病例可能对相关内部目标进行机器人US成像。通过重新规划射束以考虑机器人US引导的存在，95%的肝脏SABR病例在分次治疗期间进行US成像可能是一种选择。
