Biodistribution and radiation dosimetry of the synthetic nonmetabolized amino acid analogue Anti-18F-FACBC in humans

The synthetic leucine amino acid analog anti- 1-amino-3-F-18-fluorocyclobutane-1-carboxylic acid (anti-(18) F-FACBC) is a recently developed ligand that permits the evaluation of the L-amino acid transport system. This study evaluated the whole-body radiation burden of anti-F-18-FACBC in humans. Methods: Serial whole-body PET/CT scans of 6 healthy volunteers (3 male and 3 female) were acquired for 2 h after a bolus injection of anti-F-18-FACBC (366 +/- 51 MBq). Organ-specific time-activity curves were extracted from the reconstructed data and integrated to evaluate the individual organ residence times. A uniform activity distribution was assumed in the body organs with urine collection after the study. Estimates of radiation burden to the human body were calculated on the basis of the recommendations of the MIRD committee. The updated dynamic bladder model was used to calculate dose to the bladder wall. Results: All volunteers showed initially high uptake in the pancreas and liver, followed by rapid clearance. Skeletal muscle and bone marrow showed lower and prolonged uptake, with clearance dominated by the tracer half-life. The liver was the critical organ, with a mean absorbed dose of 52.2 mu Gy/MBq. The estimated effective dose was 14.1 mu Sv/ MBq, representing less than 20% of the dose limit recommended by the Radioactive Drug Research Committee for a 370-MBq injection. Bladder excretion was low and initially observed 6 min after injection, well after peak tracer uptake in the body organs. Conclusion: The PET whole-body dosimetry estimates indicate that an approximately 370-MBq injection of anti-F-18-FACBC yields good imaging and acceptable dosimetry. The nonmetabolized nature of this tracer is favorable for extraction of relevant physiologic parameters from kinetic models.