Development of an articulated neuro-navigation system

通过断层摄影检查可以很容易地获得有关受影响部分的确切位置的可视化信息。然而，在神经外科手术过程中，到达与MRI或CT图像相对应的大脑中的确切位置并不是一件容易的事情。在本研究中，我们开发了一个计算机辅助的立体定向导航系统，该系统包括一个关节指针，一个显示装置和一台个人计算机，它计算指针在大脑上的位置，并将位置标记叠加在断层图像上。铰接臂有六个转动关节，每个关节通过管道依次连接。通过电位器测量每个关节的旋转角度，并通过八通道A/D转换器将读数提供给计算机。在手术过程中，手臂尖端的位置自动转换为CT坐标，并在屏幕上用十字光标真实的显示。 关于我们 从屏幕上同时显示的六个切片中选择相应的平面。为了实现从臂基坐标系到机架坐标系的坐标转换，我们在头部表面放置了三个校准标记：一个在鼻根处，两个在耳朵处。利用这些校准点的图像，计算机在手术开始之前计算坐标转换矩阵。当使用该系统在颅骨上寻找最佳切口位置时，可以缩短指针尖端，从而在不将尖端插入头部的情况下假想进入位于深部的肿瘤。为了减少由于硬件不准确而引起的位置误差，我们采用了一种新的关节，带有线性度更好的电位器和角度校准手段。为了减少手术过程中头部移动引起的误差，我们增加了软件方法来重新校准坐标转换。我们还试图从CT切片重建头部表面，以便于三维视图。除了重建表面所需的计算时间外，这种尝试在手术设计上是成功的。本研究开发和改进的导航系统将在精确的外科手术中特别是在神经外科领域中具有实用价值。少

Visualized information about exact position of the affected part can be easily obtained through tomographic examinations. Nevertheless, during the neurosurgical procedures, it is not an easy task to reach the exact position in the brain that corresponds to the MRI or CT images. In this research, we developed a computer assisted stereotactic guiding for on-line surgical navigation.The system consists of an articulated pointer, a display apparatus and a personal computer which calculates the position of the pointer on the brain and overlays the positional marker on the tomographical images. The articulated arm has six revolute joints; each of the joints is successively connected by pipes. The revolution angle of each joint is measured through potentiometers and the readings are given to the computer through an eight-channel A/D converter. During surgery, the position of the arm tip is translated automatically into the CT coordinate and displayed in real time with a cross-cursor on the co … More rresponding plane, selected from six slices simultaneously displayed on the screen. To get the coordinate conversion, from the arm-base coordinate system to the gantry coordinate, we put three calibration makers on the surface of the head: one on the nasion, two on the ears. Using the image of these calibration points, the computer calculates the coordinate conversion matrix prior to the starting of the surgery.When this system is used to find the best position in making an incision on the skull, the pointer-tip can be shortened to have an imaginary access to a deeply-seated tumor without inserting the tip into the head. To lessen the positional error due to hardware inaccuracy, we adopted a new joints with potentiometers of better linearity and with angular calibration means. To lessen the error due to the move of the head during surgery, we added software means to re-calibrate the coordinate conversion. We also attempted to reconstruct the surface of the head from the CT slices to facilitate a three dimensional view. This attempt was successful in designing the operation, except for the computational time required to reconstruct the surface.The navigation system developed and improved in this research will be practical in use for the accurate surgical operation especially in neurosurgical field. Less