Development of an articulated neuro-navigation system

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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