Robot Assisted Multi-view 3D Echocardiography

超声心动图仍然是心功能分析和图像引导干预中最广泛使用的图像方式。超声心动图的优点包括没有电离辐射、便携、低成本和比其他方式更高的时间分辨率。超声技术的最新发展使心脏的三维（3D）采集成为可能，从而可以可视化复杂的心脏解剖结构，并在3D空间中分析心脏运动的复杂组合。一些研究表明，与基于二维采集的分析相比，3D图像采集*改善了体积分析。与计算机断层扫描和磁共振成像相比，3D超声心动图的主要局限性包括有限的视场（FOV），依赖于频繁受限的声窗，以及较差的信噪比。由于视野有限，单次超声心动图扫描可能不足以覆盖心脏的整个几何形状。为了增加视场，我们目前的工作使用光学跟踪系统来对齐多个超声波扫描，而不依赖于任何图像信息进行对齐。一组附着在超声换能器上的标记通过多摄像头光学跟踪系统在三维空间中进行跟踪。配准后，使用小波传感器融合算法将这些视图合并成均匀采样的体积数据集。不幸的是，光学跟踪*系统受到视线限制，这使得很难在手术室条件下使用这种技术。其他限制是：(1)依赖于患者相对于相机的位置的遮挡问题，(2)无法自动扫描程序，数字化过程纯粹是手动的，以及(3)超声医师在长时间操作探头时疲劳。为了解决这些限制，我们建议将超声波探头安装在医疗机械臂上。这里的主要想法是，超声波探头的3D跟踪将由机器人编码器执行，不需要在患者周围部署多个摄像头。这样就不会有光学遮挡的问题，而且这个机械臂可以让我们实现一些数字化功能的自动化。通过使用该医疗机器人，我们将重点研究：(1)开发新的半自主多视图融合算法；(2)利用人机合作减少超声医师疲劳。

Echocardiography remains*the most widely used image modality for cardiac functional analysis and*image-guided interventions. The advantages of echocardiography include lack of*ionizing radiation, portability, low cost, and higher temporal resolution than*other modalities. Recent developments in ultrasound technology enabled*three-dimensional (3D) acquisitions of the heart, which allow visualization of*the complex cardiac anatomy, and analysis of the complex combination of cardiac*motions in 3D space. Several studies have shown that 3D image acquisition*improves volumetric analysis, in comparison to the analysis based on a*two-dimensional acquisition. Major limitations of the 3D*echocardiography in comparison to computed tomography and magnetic*resonance imaging include limited field of view (FOV), reliance on*frequently limited acoustic windows, and poor signal to noise ratio. Due*to limited FOV, a single echocardiography scan may not be enough to cover the*whole geometry of the heart. To increase the FOV our current work uses an optical tracking system to align multiple ultrasound scans that does not rely on any image information for alignment. A set of markers attached to the ultrasound transducer are tracked in 3D space by a multi-camera optical tracking system. Once registered, a wavelet sensor fusion algorithm is used to combined those views into a uniformly sampled volumetric data set. Unfortunately optical tracking*systems are subject to the line-of-sight limitation which make it difficult to use this technique in operating room conditions. Other limitations are: (1) occlusion problems that depend on the patient positioning relative to the cameras, (2) inability to automate scanning procedures, the digitizing process is purely manual, and (3) sonographer fatigue during long manipulations of the probe. To*solve these limitations, we propose to install the ultrasound probe on a*medical robotic arm. The main idea here is that the ultrasound*probe 3D tracking will be performed by the robot encoders and will not require*the deployment of multiple cameras around the patient. There will be no optical*occlusion problems and the arm will allow us to automate some of the digitizing*functions. By using this medical robot, we will focus our research on the*following: (1) develop new semi-autonomous multi-view*fusion algorithms, (2) reduce sonographer fatigue*using human-robot cooperation.