Sun Hai, Roberts David W, Farid Hany, Wu Ziji, Hartov Alex, Paulsen Keith D
Thayer School of Engineering, Dartmouth College, Hanover, New Hampshire, USA.
Neurosurgery. 2005 Jan;56(1 Suppl):86-97; discussion 86-97. doi: 10.1227/01.neu.0000146263.98583.cc.
To measure and compensate for soft tissue deformation during image-guided neurosurgery, we have developed a novel approach to estimate the three-dimensional (3-D) topology of the cortical surface and track its motion over time.
We use stereopsis to estimate the 3-D cortical topology during neurosurgical procedures. To facilitate this process, two charge-coupled device cameras have been attached to the binocular optics of a stereoscopic operating microscope. Before surgery, this stereo imaging system is calibrated to obtain the extrinsic and intrinsic camera parameters. During surgery, the 3-D shape of the cortical surface is automatically estimated from a stereo pair of images and registered to the preoperative image volume to provide navigational guidance. This estimation requires robust matching of features between the images, which, when combined with the camera calibration, yields the desired 3-D coordinates. After the 3-D cortical surface has been estimated from stereo pairs, its motion is tracked by comparing the current surface with its previous locations.
We are able to estimate the 3-D topology of the cortical surface with an average error of less than 1.2 mm. Executing on a 1.1-GHz Pentium machine, the 3-D estimation from a stereo pair of 1024 x 768 resolution images requires approximately 60 seconds of computation. By applying stereopsis over time, we are able to track the motion of the cortical surface, including the pulsatile movement of the cortical surface, gravitational sag, tissue bulge as a result of increased intracranial pressure, and the parenchymal shape changes associated with tissue resection. The results from 10 surgical patients are reported.
We have demonstrated that a stereo vision system coupled to the operating microscope can be used to efficiently estimate the dynamic topology of the cortical surface during surgery. The 3-D surface can be coregistered to the preoperative image volume. This unique intraoperative imaging technique expands the capability of the current navigational system in the operating room and increases the accuracy of anatomic correspondence with preoperative images through compensation for brain deformation.
为了在图像引导的神经外科手术中测量并补偿软组织变形，我们开发了一种新颖的方法来估计皮质表面的三维（3-D）拓扑结构，并跟踪其随时间的运动。
我们在神经外科手术过程中使用立体视觉来估计三维皮质拓扑结构。为便于此过程，两台电荷耦合器件相机已连接到立体手术显微镜的双目光学系统。手术前，对该立体成像系统进行校准以获取相机的外部和内部参数。手术过程中，从一对立体图像中自动估计皮质表面的三维形状，并将其与术前图像体积配准以提供导航引导。这种估计需要图像之间特征的稳健匹配，将其与相机校准相结合，可得出所需的三维坐标。从立体图像对估计出三维皮质表面后，通过将当前表面与其先前位置进行比较来跟踪其运动。
我们能够估计皮质表面的三维拓扑结构，平均误差小于1.2毫米。在1.1 GHz奔腾机器上执行时，从一对分辨率为1024×768的立体图像进行三维估计大约需要60秒的计算时间。通过随时间应用立体视觉，我们能够跟踪皮质表面的运动，包括皮质表面的脉动运动、重力下垂、颅内压升高导致的组织隆起以及与组织切除相关的实质形状变化。报告了10例手术患者的结果。
我们已经证明，与手术显微镜耦合的立体视觉系统可用于在手术期间有效地估计皮质表面的动态拓扑结构。三维表面可与术前图像体积进行配准。这种独特的术中成像技术扩展了手术室当前导航系统的能力，并通过补偿脑变形提高了与术前图像的解剖对应准确性。
