Dosimetry of [F]TRACK, the first PET tracer for imaging of TrkB/C receptors in humans.

Background: Reduced expression or impaired signalling of tropomyosin receptor kinases (Trk receptors) are found in a vast spectrum of CNS disorders. [F]TRACK is the first PET radioligand for TrkB/C with proven in vivo brain penetration and on-target specific signal. Here we report dosimetry data for [F]TRACK in healthy humans. 6 healthy participants (age 22-61 y, 3 female) were scanned on a General Electric Discovery PET/CT 690 scanner. [F]TRACK was synthesized with high molar activities (A = 250 ± 75 GBq/µmol), and a dynamic series of 12 whole-body scans were acquired after injection of 129 to 147 MBq of the tracer. Images were reconstructed with standard corrections using the manufacturer's OSEM algorithm. Tracer concentration time-activity curves (TACs) were obtained using CT-derived volumes-of-interest. Organ-specific doses and the total effective dose were estimated using the Committee on Medical Internal Radiation Dose equation for adults and tabulated Source tissue values (S values).

Results: Average organ absorbed dose was highest for liver and gall bladder with 6.1E-2 (± 1.06E-2) mGy/MBq and 4.6 (± 1.18E-2) mGy/MBq, respectively. Total detriment weighted effective dose E was 1.63E-2 ± 1.68E-3 mSv/MBq. Organ-specific TACs indicated predominantly hepatic tracer elimination.

Conclusion: Total and organ-specific effective doses for [F]TRACK are low and the dosimetry profile is similar to other F-labelled radio tracers currently used in clinical settings.