The most important imaging technology for GKNS continues to be magnetic resonance. The introduction of 3 Tesla machines permits quicker studies with better signal to noise ratio. The more powerful magnet increases the chances of heating the points of contact between patient and frame, but this has been solved with non-conducting nuts. There are several sequences for special functions. CISS studies are optimal for demonstrating cranial nerves in their passage through the subarachnoid space. FLAIR studies facilitate the distinction between CSF and edema due to inflammation. DTI permits the visualization of nerve fiber tracts. This has at least two current applications. In treatment planning of visible lesions, DTI permits a more efficient avoidance of important tracts. In functional work, tracts can be used to improve the definition of functional targets. Non stereotactic MRI can be imported into GammaPlan and co-registered to a non-distorted CT image.