Earlier work demonstrated that physical restraint, by itself, cannot entirely suppress head movement during brain imaging. Accurate knowledge of the position of the head throughout the scanning interval could, however, permit corrections for such movement to be computed and image """"""""blur"""""""" due to such motions removed. In this reporting period, we performed two studies essential to the practical implementation of this correction method. In the first study, head movement was tracked for 45 minutes in each of 13 normal volunteers studied both with and without head restraint during a simulated brain imaging. Patterns of head movement in these subjects established the need for a relatively high rate of sampling of head position and the continued use of physical restraint in order to minimize the amount of correction computation. In the second continuing study, we are evaluating a spatial tracking system that operates on a different physical principle than used previously and that may be less susceptible to environmental factors. If this, or another, device works effectively in the actual scanning environment, then a method must be found to attach the position transducer to the subject's head without interfering with the scanning process or with other apparatus used to stimulate and monitor the subject. Work on methods for repositioning subjects from one scanning session to next and from one scanner to another was also continued during this period.
