A recent tracer for PSMA PET-CT, 18F-PSMA-1007, offers more advantages regarding biokinetics and production when compared to the standard tracer 68Ga-PSMA-11. A new study provides insight on the dosimetry and biokinetics of 18F-PSMA-1007.
The study involved 12 patients with prostate cancer who were given injections of 4 MBq/kg 18F-PSMA-1007. Up to five and a half hours following the injection, eight PET-CT scans were performed on the patients along with concomitant blood sampling; urine samples were also collected until the next morning.
The PET images were used to show organs with a high uptake of 18F-PSMA-1007 along with volumes of interest for radiation-sensitive organs. These images including blood and urine samples were used in the creation of a biokinetic compartment model. Both absorbed and effective doses were measured, and researchers calculated time-activity curves and time-integrated activity coefficients for all delineated organs.
High activity was seen in the liver, kidneys, spleen, salivary glands, lacrimal glands, and parts of the small intestine. Elimination through urine was 8% of injected activity in 20 h. The highest absorbed doses coefficients were found in the lacrimal glands, kidneys, salivary glands, spleen, and liver, and the effective dose coefficient was 25 µSv/MBq.
Researchers concluded that an effective dose of 18F-PSMA-1007 is 6.0-8.0 mSv for a typical patient weighing 80 kg injected with 3-4 MBq/kg.