Department of Computing, Imperial College London, UK.
Comput Med Imaging Graph. 2010 Jan;34(1):61-8. doi: 10.1016/j.compmedimag.2009.08.002. Epub 2009 Sep 20.
A novel system for image guidance in totally endoscopic coronary artery bypass (TECAB) is presented. Key requirement is the availability of 2D-3D registration techniques that can deal with non-rigid motion and deformation. Image guidance for TECAB is mainly required before the mechanical stabilisation of the heart, when the most dominant source of misregistration is the deformation and non-rigid motion of the heart. To augment the images in the endoscope of the da Vinci robot, we have to find the transformation from the coordinate system of the preoperative imaging modality to the system of the endoscopic cameras. In a first step we build a 4D motion model of the beating heart. Intraoperatively we can use the ECG or video processing to determine the phase of the cardiac cycle, as well as the heart and respiratory frequencies. We then take the heart surface from the motion model and register it to the stereo endoscopic images of the da Vinci robot resp. of a validation system using photo-consistency. To take advantage of the fact that there is a whole image sequence available for registration, we use the different phases together to get the registration. We found the similarity function to be much smoother when using more phases. This also showed promising behaviour in convergence tests. Images of the vessels available in the preoperative coordinate system can then be transformed to the camera system and projected into the calibrated endoscope view using two video mixers with chroma keying. It is hoped that the augmented view can improve the efficiency of TECAB surgery and reduce the conversion rate to more conventional procedures.
介绍了一种用于完全内窥镜冠状动脉旁路移植术（TECAB）的图像引导新系统。关键要求是具备能够处理非刚性运动和变形的 2D-3D 配准技术。TECAB 的图像引导主要需要在心脏机械稳定之前进行，此时最主要的配准误差源是心脏的变形和非刚性运动。为了增强达芬奇机器人内窥镜中的图像，我们必须找到从术前成像模式的坐标系到内窥镜摄像机系统的转换。在第一步中，我们构建了跳动心脏的 4D 运动模型。术中，我们可以使用心电图或视频处理来确定心脏周期的阶段，以及心脏和呼吸频率。然后，我们从运动模型中获取心脏表面，并使用照片一致性将其注册到达芬奇机器人的立体内窥镜图像或验证系统中。为了利用有整个图像序列可用于注册的事实，我们使用更多的阶段来共同获得注册。我们发现使用更多阶段时相似性函数更加平滑。这在收敛测试中也表现出了有希望的行为。在术前坐标系中可用的血管图像可以转换到相机系统，并使用带有色度键控的两个视频混合器将其投影到校准的内窥镜视图中。希望增强视图可以提高 TECAB 手术的效率，并降低转换为更传统程序的比率。
