Institute of Medical Technology, Hamburg University of Technology, Hamburg, Germany.
Institute for Robotics and Cognitive Systems, Universität zu Lübeck, Lübeck, Germany.
Int J Comput Assist Radiol Surg. 2017 Jan;12(1):149-159. doi: 10.1007/s11548-016-1455-7. Epub 2016 Jul 12.
Advances in radiation therapy delivery systems have enabled motion compensated SBRT of the prostate. A remaining challenge is the integration of fast, non-ionizing volumetric imaging. Recently, robotic ultrasound has been proposed as an intra-fraction image modality. We study the impact of integrating a light-weight robotic arm carrying an ultrasound probe with the CyberKnife system. Particularly, we analyze the effect of different robot poses on the plan quality.
A method to detect the collision of beams with the robot or the transducer was developed and integrated into our treatment planning system. A safety margin accounts for beam motion and uncertainties. Using strict dose bounds and the objective to maximize target coverage, we generated a total of 7650 treatment plans for five different prostate cases. For each case, ten different poses of the ultrasound robot and transducer were considered. The effect of different sets of beam source positions and different motion margins ranging from 5 to 50 mm was analyzed.
Compared to reference plans without the ultrasound robot, the coverage typically drops for all poses. Depending on the patient, the robot pose, and the motion margin, the reduction in coverage may be up to 50 % points. However, for all patient cases, there exist poses for which the loss in coverage was below 1 % point for motion margins of up to 20 mm. In general, there is a positive correlation between the number of treatment beams and the coverage.
While the blocking of beam directions has a negative effect on the plan quality, the results indicate that a careful choice of the ultrasound robot's pose and a large solid angle covered by beam starting positions can offset this effect. Identifying robot poses that yield acceptable plan quality and allow for intra-fraction ultrasound image guidance, therefore, appears feasible.
放射治疗输送系统的进步使前列腺的运动补偿 SBRT 成为可能。仍然存在的挑战是快速、非电离容积成像的集成。最近，机器人超声已被提议作为一种分次内图像模态。我们研究了将携带超声探头的轻量级机器人手臂与 CyberKnife 系统集成的影响。特别是，我们分析了不同机器人姿势对计划质量的影响。
开发了一种检测光束与机器人或换能器碰撞的方法，并将其集成到我们的治疗计划系统中。安全裕度考虑了光束运动和不确定性。使用严格的剂量边界和最大化目标覆盖的目标，我们为五个不同的前列腺病例生成了总共 7650 个治疗计划。对于每个病例，考虑了超声机器人和换能器的十种不同姿势。分析了不同的光束源位置集和从 5 到 50mm 的不同运动裕度的效果。
与没有超声机器人的参考计划相比，所有姿势的覆盖通常都会下降。根据患者、机器人姿势和运动裕度的不同，覆盖范围的减少可能高达 50%点。然而，对于所有患者病例，对于运动裕度高达 20mm 的情况，存在覆盖范围损失低于 1%点的姿势。一般来说，治疗光束的数量与覆盖范围之间存在正相关。
虽然阻挡光束方向对计划质量有负面影响，但结果表明，仔细选择超声机器人的姿势和光束起始位置覆盖的大立体角可以抵消这种影响。因此，识别出可接受的计划质量并允许进行分次内超声图像引导的机器人姿势是可行的。
