Reliability of rubidium-82 PET/CT for renal perfusion determination in healthy subjects

BACKGROUND: Changes in renal perfusion may play a pathophysiological role in hypertension and kidney disease, however to date, no method for renal blood flow (RBF) determination in humans has been implemented in clinical practice. In a previous study, we demonstrated that estimation of renal perfusion based on a single positron emission tomography/computed tomography (PET/CT) scan with Rubidium-82 ((82)Rb) is feasible and found an approximate 5% intra-assay coefficient of variation for both kidneys, indicative of a precise method.This study’s aim was to determine the day-to day variation of (82)Rb PET/CT and to test the method’s ability to detect increased RBF induced by infusion of amino acids. METHODS: Seventeen healthy subjects underwent three dynamic (82)Rb PET/CT scans over two examination days comprising: Day A, a single 8-minute dynamic scan and Day B, two scans performed before (baseline) and after RBF stimulation by a 2-hour amino acid-infusion. The order of examination days was determined by randomization. Time activity curves for arterial and renal activity with a 1-tissue compartment model were used for flow estimation; the K(1) kinetic parameter representing renal (82)Rb clearance. Day-to-day variation was calculated based on the difference between the unstimulated K(1) values on Day A and Day B and paired t-testing was performed to compare K(1) values at baseline and after RBF stimulation on Day B. RESULTS: Day-to-day variation was observed to be 5.5% for the right kidney and 6.0% for the left kidney (n = 15 quality accepted scans). K(1) values determined after amino acid-infusion were significantly higher than pre-infusion values (n = 17, p = 0.001). The mean percentage change in K(1) from baseline was 13.2 ± 12.9% (range − 10.4 to 35.5) for the right kidney; 12.9 ± 13.2% (range − 15.7 to 35.3) for the left kidney. CONCLUSION: Day-to-day variation is acceptably low. A significant K(1) increase from baseline is detected after application of a known RBF stimulus, indicating that (82)Rb PET/CT scanning can provide a precise method for evaluation of RBF and it is able to determine changes herein. CLINICAL TRIAL REGISTRATION: EU Clinical Trials Register, 2017-005008-88. Registered 18/01/2018.