Make an evaluation of CTT (EMI Scanner). Follow a protocol already developed by the NCI for the clinical evaluation of this EMI equipment in the following situations: (1) In patients with definite symptons that suggest the possibility of space occupying introcranial lesions, the EMI Scanner results are to be compared to brain scans. (2) In patients with a minimal but a significant probability of a primary or metastatic brain tumor. (3) Normal persons EMI scan will be done to determine normal levels of absorption in defference areas of the brain.