Effects of head movements measured during PET scans

The authors have measured the head movements of patients during PET scans, using two cameras fixed above the bed. The cameras observe motion of infra-red reflectors attached to a mouthpiece attached to the patient's upper jaw by a tooth splint. The entire assembly is completely rigid, both for patients with dentures and for patients with their own teeth. Most patients were able to tolerate the extra inconvenience of the mouthpiece, although some refused to try it. The effects of head motion arise both in re-positioning the patient between scans (e.g. between a raclopride and a fluorodopa scan) and during the scans. Typically the authors measure uptake over a 30-minute period for raclopride, and during 10-minute intervals for fluorodopa. Patient repositioning errors of up to 7-10 mm were observed between scans, and even during a short 10-minute scan, the patients may slip 7-10 mm within their face masks. Experiences with measuring the motion are explored.