ABSTRACT
PURPOSE: Positron emission tomography-computed tomography (PET-CT) using prostate-specific membrane antigen (PSMA) ligands is a method for imaging prostate cancer. A recent tracer, 18 F-PSMA-1007, offers advantages concerning production and biokinetics compared to the standard tracer (68 Ga-PSMA-11). Until now, radiation dosimetry data for this ligand was limited to the material of three healthy volunteers. The purpose of this study is to study the biokinetics and dosimetry of 18 F-PSMA-1007. METHODS: Twelve patients with prostate cancer were injected with 4 MBq/kg 18 F-PSMA-1007. Eight PET-CT scans with concomitant blood sampling were performed up to 330 min after injection. Urine was collected until the following morning. Volumes of interest for radiation-sensitive organs and organs with high uptake of 18 F-PSMA-1007 were drawn in the PET images. A biokinetic compartment model was developed using activity data from PET images and blood and urine samples. Time-activity curves and time-integrated activity coefficients for all delineated organs were calculated. The software IDAC-dose 2.1 was used to calculate the absorbed and effective doses. RESULTS: High concentrations of activity were noted in the liver, kidneys, parts of the small intestine, spleen, salivary glands, and lacrimal glands. The elimination through urine was 8% of injected activity in 20 h. The highest absorbed doses coefficients were in the lacrimal glands, kidneys, salivary glands, liver, and spleen (98-66 µGy/MBq). The effective dose coefficient was 25 µSv/MBq. CONCLUSION: The effective dose of 18 F-PSMA-1007 is 6.0-8.0 mSv for a typical patient weighing 80 kg injected with 3-4 MBq/kg.
