Image guided stereotactic surgery is a less invasive method for many neurosurgical procedures as biopsy, laser therapy or hyperthermia. This method precisely localizes a needle to the target lesion after measuring target position with CT/MR images. We have developed a needle insertion manipulator system for CT-guided stereotactic surgery. Our system consists of a needle insertion manipulator and its PC-based controller. The manipulator, which is placed on a stereotactic frame, has six degree-of-freedom of movement: X, Y, Z for needle localization, φ, θ for needle direction, and S for needle insertion. As using stepping motors for all axes, the manipulator has a positioning precision of less than0.1mm. In case of accident, this system can immediately stop the motion of manipulator by cutting off the power supply to motors, and axes are held rigidly to avoid interference to the patient and surgeons. A phantom study using X-ray CT images has shown the following: 1)The top of the needle was located to the target with 1.0mm of error: it is sufficient for most stereotactic operations, considering CT image resolution(0.5mm per pixel). 2)No artifact on CT images caused by the manipulator was found. 3)The manipulator was small enough to be set in CT gantry(600mm in diameter).

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A method of detection of the gazing direction is proposed. It is shown that the gazing direction can be determined from the distance between the images by the corneal and the scleral reflections. This method can be applied to an off-body eye tracker. The deflection angle of the gazing direction within 30 degrees from the front direction is detectable with an error less than 10%.

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