Whole-body biodistribution and the influence of body activity on brain kinetic analysis of the 11C-PiB PET scan.

Dynamic 11C-PiB PET imaging with kinetic analysis has been performed for accurate quantification of amyloid binding in patients with Alzheimer's disease (AD). In this study, we measured the whole-body biodistribution of 11C-PiB in nine subjects. We then evaluated the effect of body activity on quantitative accuracy of brain 11C-PiB three-dimensional (3D) dynamic PET. Based on clinical biodistribution data, we conducted phantom experiments to estimate the effect of body activity on quantification of the brain 3D dynamic 11C-PiB PET data and the error introduced by body activity using six different PET camera models. One of the PET cameras was used to acquire 11C-PiB brain 3D dynamic PET data on a patient with AD. We calculated the distribution volume ratio (DVR) in two kinetic methods using both the original human time-activity-curve (TAC) data and the TAC corrected for the error caused by body activity. In the early phase, both healthy subjects and patients with AD showed a biodistribution of 11C-PiB that reflected regional blood flow. In the simulated early phase of the phantom experiments, activity outside the field of view led to a maximum 6.0% overestimation of brain activity in the vertex region. Conversely, the effect of body activity on the DVR estimate was small (≤1.2%), probably because the tested kinetic methods did not rely heavily on early phase data. These results indicate that the effect of body activity on brain 11C-PiB PET quantification is generally small and that it depends on the method of kinetic analysis, the region of interest, and the PET camera model used.