X-ray controlled implantation of the brain stem.

Using X-rays to improve accuracy of stereotaxic implantation of the brain stem of Macaca irus monkeys overcomes the problems of moveable brain stem and inaccurate fixation in the stereotaxic frame. The method is independent of standard atlases and correct ear bar fixation. The key to the method is the establishment of a nomogram which relates the implantation target to bony landmarks. The nomogram is established by X-ray contrast studies which outline the brain stem, the implantation target in the brain stem being decided by superimposed histology. This target is nomographically related to bony landmarks seen both on the contrast X-ray and on a plain X-ray taken later at implantation with the monkey in the stereotaxic frame. Being able to locate the target on this plain X-ray, and having included on the X-ray a metal marker, the stereotaxic coordinates of which are known, the distance can be measured (allowing for X-ray magnification) between target and stereotaxic marker and thus one computes the target coordinates. Accuracy of implantation according to these coordinates is monitored with further plain X-rays.