Abstract: Apparatus is disclosed for maintaining the position of a patient during a dical procedure such as imaging by position emission tomography (PET) or magnetic resonance imaging (MRI) or radiotherapeutic uses of medical procedures wherein maintaining a portion of the patient's body in a stationary position is important. The apparatus includes a system for tracking motion of the particular body portion of interest, such as the head, a computer for receiving signals from the tracking system, and determining if undesired motion of the body portion has occurred and, if so, issuing a corrective signal which through a plurality of motors effects repositioning of the body portion to the desired location. This monitoring and repositioning may take place at a very high frequency. A particular contemplated use is immobilizing and positioning of the head during brain scans. An associated method is disclosed.