Institute for Robotics and Cognitive Systems, University of Luebeck, Luebeck, Germany.
Fraunhofer Research Institution for Individualized and Cell-Based Medical Engineering IMTE, Luebeck, Germany.
Phys Med Biol. 2021 Apr 23;66(9). doi: 10.1088/1361-6560/abf277.
Real-time volumetric (4D) ultrasound has shown high potential for diagnostic and therapy guidance tasks. One of the main drawbacks of ultrasound imaging to date is the reliance on manual probe positioning and the resulting user dependence. Robotic assistance could help overcome this issue and facilitate the acquisition of long-term image data to observe dynamic processesover time. The aim of this study is to assess the feasibility of robotic probe manipulation and organ motion quantification during extended imaging sessions. The system consists of a collaborative robot and a 4D ultrasound system providing real-time data access. Five healthy volunteers received liver and prostate scans during free breathing over 30 min. Initial probe placement was performed with real-time remote control with a predefined contact force of 10 N. During scan acquisition, the probe position was continuously adjusted to the body surface motion using impedance control. Ultrasound volumes, the pose of the end-effector and the estimated contact forces were recorded. For motion analysis, one anatomical landmark was manually annotated in a subset of ultrasound frames for each experiment. Probe contact was uninterrupted over the entire scan duration in all ten sessions. Organ drift and imaging artefacts were successfully compensated using remote control. The median contact force along the probe's longitudinal axis was 10.0 N with maximum values of 13.2 and 21.3 N for liver and prostate, respectively. Forces exceeding 11 N only occurred in 0.3% of the time. Probe and landmark motion were more pronounced in the liver, with median interquartile ranges of 1.5 and 9.6 mm, compared to 0.6 and 2.7 mm in the prostate. The results show that robotic ultrasound imaging with dynamic force control can be used for stable, long-term imaging of anatomical regions affected by motion. The system facilitates the acquisition of 4D image dataover extended scanning periods for the first time and holds the potential to be used for motion monitoring for therapy guidance as well as diagnostic tasks.
实时容积（4D）超声在诊断和治疗指导任务中显示出巨大潜力。迄今为止，超声成像的主要缺点之一是依赖于手动探头定位，从而导致对用户的依赖。机器人辅助可以帮助克服这个问题，并促进长期图像数据的获取，以观察随时间推移的动态过程。本研究旨在评估在扩展成像过程中进行机器人探头操作和器官运动量化的可行性。该系统由协作机器人和提供实时数据访问的 4D 超声系统组成。五名健康志愿者在自由呼吸期间接受了 30 分钟以上的肝脏和前列腺扫描。初始探头放置是通过具有预设接触力为 10N 的实时远程控制进行的。在扫描采集期间，使用阻抗控制连续调整探头位置以适应体表运动。记录了超声体积、末端执行器的姿态和估计的接触力。对于运动分析，在每个实验的一部分超声帧中手动注释一个解剖学标记。在所有十次扫描中，探头接触在整个扫描过程中都没有中断。使用远程控制成功补偿了器官漂移和成像伪影。沿探头纵轴的平均接触力为 10.0N，肝脏和前列腺的最大力分别为 13.2N 和 21.3N。只有 0.3%的时间力超过 11N。与前列腺相比，肝脏中的探头和标记运动更为明显，中位数四分位间距分别为 1.5mm 和 9.6mm，而前列腺分别为 0.6mm 和 2.7mm。结果表明，具有动态力控制的机器人超声成像可用于受运动影响的解剖区域的稳定、长期成像。该系统首次实现了在扩展扫描期间采集 4D 图像数据，具有用于运动监测以指导治疗和诊断任务的潜力。
