Al¹⁸F-NODA-butyric acid: Biological evaluation of a new PET renal radiotracer

Introduction: Renal scintigraphy is an important imaging modality for the diagnosis and management of a variety of renal diseases including obstruction and renovascular hypertension as well as the evaluation of absolute and relative kidney function. The goal of this work was to evaluate Al¹⁸F-NODA-butyric acid (Al¹⁸F-1) as a potential PET tracer to image the kidneys and monitor renal function by comparing its pharmacokinetic properties with those of ¹³¹I-o-iodohippurate (¹³¹I-OIH), the radioactive standard for the measurement of effective renal plasma flow. Methods: Al¹⁸F-1 was prepared in aqueous conditions using a one-pot Al¹⁸F-radiofluorination method and its radiochemical purity was determined by HPLC. Biodistribution studies, using ¹³¹I-OIH as an internal control, were performed in normal rats and in rats with renal pedicle ligation. In vitro stability and metabolism of Al¹⁸F-1 were analyzed by HPLC. Dynamic microPET/CT studies were conducted in normal rats. Results: Al¹⁸F-1 showed excellent stability in vitro and in vivo. Biodistribution studies in normal rats and in rats with simulated renal failure confirmed that Al¹⁸F-1 was exclusively cleared through the renal-urinary pathway and that the hepatic/gastrointestinal activity was less for Al¹⁸F-1 than for ¹³¹I-OIH both at 10 and 60min. Dynamic PET showed a rapid transit of Al¹⁸F-1 through the kidneys into the bladder. Conclusion: These results suggest that the easily labeled Al¹⁸F-based compounds provide a highly promising approach for the development of a PET renal radiotracer that combines superior imaging qualities with a reliable measure of effective renal plasma flow.