Work during this period focussed on methods for correcting PET and SPECT image data for patient motion during the scanning period. Plans and specifications were developed for a light-based motion sensing system (Goldstein) that would permit patient head movement to be monitored during a scan. A prototype system based on this concept was fabricated and initial tests of the system were undertaken. In parallel, several commercial position sensing systems were evaluated in the scanning environment to determine their suitability for making such measurements. One system utilized a pulsed DC magnetic field to make position measurements but this system failed when operated in and around the PET imaging gantry. The second system, based on an acoustic principle, operated successfully in the scanning environment but was attended with a perceptible audio signal thought likely to produce unacceptable interference in brain stimulation studies. This method, however, has not been ruled out and does possess a number of virtues not shared by other method, e.g., a very high position accuracy. One or the other of these methods will be selected, based on testing in volunteers, to make continuous measurements of head position from which corrections factors will be computed to remove patient motion artifacts from PET and SPECT brain image data.
