Performing radiosynthesis in microvolumes to maximize molar activity of tracers for positron emission tomography.

Positron emission tomography (PET) is a molecular diagnostic imaging technology to quantitatively visualize biological processes in vivo . For many applications, including imaging of low tissue density targets (e.g. neuroreceptors), imaging in small animals, and evaluation of novel tracers, the injected PET tracer must be produced with high molar activity to ensure low occupancy of biological targets and avoid pharmacologic effects. Additionally, high molar activity is essential for tracers with lengthy syntheses or tracers transported to distant imaging sites. We show that radiosynthesis of PET tracers in microliter volumes instead of conventional milliliter volumes results in substantially increased molar activity, and we identify the most relevant variables affecting this parameter. Furthermore, using the PET tracer [ ¹⁸ F]fallypride, we illustrate that molar activity can have a significant impact on biodistribution. With full automation, microdroplet platforms could provide a means for radiochemists to routinely, conveniently, and safely produce PET tracers with high molar activity.
Competing Interests: Competing Interests Drs. van Dam and Phelps are founders of Sofie Biosciences, Inc., Dr. Phelps is a board member of Sofie Biosciences, and Drs. van Dam and Keng are consultants to Sofie Biosciences. The Regents of the University of California have licensed technology to Sofie Biosciences that was invented by Drs. van Dam, Keng, and Lazari, and have taken equity in Sofie Biosciences as part of the licensing transaction.