Absorbed fractions for dose calculations of neuroreceptor PET studies.

A simple Monte Carlo program was constructed for the purpose of calculating absorbed fractions of relevance to neurologic positron-emission-tomography studies. The caudate, putamen, and cerebellum regions of the brain were mathematically modeled to serve as source regions for the absorbed-fraction calculations for positron-annihilation photons. The target organs were the caudate, putamen, cerebellum, brain, spine portion in the head, skull, and head. Absorbed fractions were also calculated for a uniform ring source which encircled the head phantom.