Kinetic modeling and non-invasive approach for translocator protein quantification with 11 C-DPA-713.

INTRODUCTION: 11 C-DPA-713 is a positron emission tomography (PET) radiotracer developed for imaging the expression of the translocator protein (TSPO) in glial cells, which is considered to be a marker of the neuroinflammatory burden. This study investigated the pharmacokinetic profile of 11 C-DPA-713 and evaluated kinetic modeling and non-invasive TSPO quantification using dynamic PET imaging data in the Alzheimer's disease (AD) and cognitive normal (CN) participants.

METHODS: Eleven patients with AD and 6 CN participants were examined using dynamic 11 C-DPA-713 PET imaging for 60 min with arterial blood sampling. Time-activity curves were calculated from the cerebellum and three composite regions of interest (ROIs), according to the anatomical definitions of Braak's stages 1 to 3, stage 4, stage 5, and stage 6 that correspond to the pathological stages of tangle deposition. The total distribution volume (VT ) was evaluated using compartmental modeling and graphical analysis. Reference region-based methods were implemented using an optimal area that was assumed to be void of the radiotracer target as reference tissue.

RESULTS: The concentration of radioactivity in plasma demonstrated rapid clearance. 11 C-DPA-713 peaked rapidly in the gray matter. Compartmental modeling resulted in a good fit, and the one-tissue model with estimated blood volume correction (1Tv) showed the best performance. The estimated VT obtained from the graphical plasma methods was highly correlated with that obtained from 1Tv. Reference region-based analysis was conducted using the Braak 6 area as the reference region, and the estimated non-displaceable binding potential was highly correlated with that obtained from 1Tv.

CONCLUSION: 11 C-DPA-713 possesses properties suitable for TSPO quantification with PET imaging. The Braak 6 area was shown to be a useful reference region in the patients with AD and the CN participants, and non-invasive reference tissue models using the Braak 6 area as a reference region can be employed for TSPO quantification with 11 C-DPA-713-PET imaging as an alternative to the invasive compartmental model.