Whole body [11C]-dihydrotetrabenazine imaging of baboons: biodistribution and human radiation dosimetry estimates.

Abstract

Vesicular monoamine transporter type 2 abundance quantified using the radiotracer [(11)C]-dihydrotetrabenazine (DTBZ) has been used to study diagnosis and pathogenesis of dementia and psychiatric disorders in humans. In addition, it may be a surrogate marker for insulin-producing pancreatic beta cell mass, useful for longitudinal measurements using positron emission tomography to track progression of autoimmune diabetes. To support the feasibility of long-term repeated administrations, we estimate the biodistribution and dosimetry of [(11)C]-DTBZ in humans. Five baboon studies were acquired using a Siemens ECAT camera. After transmission scanning, 165-210 MBq of [(11)C]-DTBZ were injected, and dynamic whole body emission scans were conducted. Time-activity data were used to obtain residence times and estimate absorbed radiation dose according to the MIRD model. Most of the injected tracer localized to the liver and the lungs, followed by the intestines, brain, and kidneys. The highest estimated absorbed radiation dose was in the stomach wall. The largest radiation dose from [(11)C]-DTBZ is to the stomach wall. This dose estimate, as well as the radiation dose to other radiosensitive organs, must be considered in evaluating the risks of multiple administrations.