Schoob Andreas, Laves Max-Heinrich, Kahrs Lüder Alexander, Ortmaier Tobias
Institute of Mechatronic Systems, Leibniz Universität Hannover, 30167, Hanover, Germany.
Int J Comput Assist Radiol Surg. 2016 Dec;11(12):2325-2337. doi: 10.1007/s11548-016-1420-5. Epub 2016 Jun 1.
Recent research has revealed that incision planning in laser surgery deploying stylus and tablet outperforms micromanipulator control. However, vision-based adaption to dynamic surgical scenes has not been addressed so far. In this study, scene motion compensation for tablet-based planning by means of tissue deformation tracking is discussed.
A stereo-based method for motion tracking with piecewise affine deformation modeling is presented. Proposed parametrization relies on the epipolar constraint to enforce left-right consistency in the energy minimization problem. Furthermore, the method implements illumination-invariant tracking and appearance-based occlusion detection. Performance is assessed on laparoscopic and laryngeal in vivo data. In particular, tracking accuracy is measured under various conditions such as occlusions and simulated laser cuttings. Experimental validation is extended to a user study conducted on a tablet-based interface that integrates the tracking for image stabilization.
Tracking accuracy measurement reveals a root-mean-square error of 2.45 mm for the laparoscopic and 0.41 mm for the laryngeal dataset. Results successfully demonstrate stereoscopic tracking under changes in illumination, translation, rotation and scale. In particular, proposed occlusion detection scheme can increase robustness against tracking failure. Moreover, assessed user performance indicates significantly increased path tracing accuracy and usability if proposed tracking is deployed to stabilize the view during free-hand path definition.
The presented algorithm successfully extends piecewise affine deformation tracking to stereo vision taking the epipolar constraint into account. Improved surgical performance as demonstrated for laser incision planning highlights the potential of presented method regarding further applications in computer-assisted surgery.
最近的研究表明，在激光手术中使用触控笔和平板进行切口规划比微操作器控制表现更优。然而，基于视觉对动态手术场景的适应性问题迄今尚未得到解决。在本研究中，讨论了通过组织变形跟踪对基于平板的规划进行场景运动补偿。
提出了一种基于立体视觉的运动跟踪方法，采用分段仿射变形建模。所提出的参数化依赖于极线约束，以在能量最小化问题中强制左右一致性。此外，该方法实现了光照不变跟踪和基于外观的遮挡检测。在腹腔镜和喉部体内数据上评估性能。特别是，在各种条件下（如遮挡和模拟激光切割）测量跟踪精度。实验验证扩展到在基于平板的界面上进行的用户研究，该界面集成了用于图像稳定的跟踪功能。
跟踪精度测量显示，腹腔镜数据集的均方根误差为2.45毫米，喉部数据集为0.41毫米。结果成功证明了在光照、平移、旋转和缩放变化下的立体跟踪。特别是，所提出的遮挡检测方案可以提高对跟踪失败的鲁棒性。此外，评估的用户性能表明，如果在徒手路径定义期间采用所提出的跟踪来稳定视图，则路径跟踪精度和可用性会显著提高。
所提出的算法成功地将分段仿射变形跟踪扩展到考虑极线约束的立体视觉。如激光切口规划所示的手术性能改善突出了所提出方法在计算机辅助手术进一步应用方面的潜力。
