Initial human experience with Rubidium-82 renal PET/CT imaging

Introduction Preclinical data have shown that Rubidium-82 chloride ( ⁸²Rb) is a radiotracer with high first pass extraction and slow washout in the kidneys. The goal of this study was to investigate the feasibility of human kidney imaging with ⁸²Rb positron emission tomography (PET) and obtain quantitative data of its uptake non-invasively. Methods Eight healthy volunteers underwent dynamic PET/CT imaging with ⁸²Rb. A preprogrammed pump was used to insure reproducible injections. Tissue time activity curves were generated from the renal cortex. An input function was derived from the left ventricular blood pool (LVBP), the descending thoracic aorta and the abdominal aorta. Renal blood flow was estimated by applying a two-compartment kinetic model. Results obtained with different input functions were compared. Results Radiotracer accumulation was rapid and reached a plateau within 15-30 s after the bolus entered the kidneys. The derived K1 and k2 parameters were reproducible using input functions obtained from diverse vascular locations. K1 averaged 1.98 ± 0.14 mL/min/g. The average k2 was 0.35 ± 0.11/min. Correlation between K1 values obtained from the LVBP from different bed positions when the kidneys and abdominal aorta were in the same field of view was excellent (R = 0.95). Conclusions Non-invasive quantitative human kidney imaging with ⁸²Rb PET is feasible. Advantages of renal PET with ⁸²Rb include excellent image quality with high image resolution and contrast. ⁸²Rb has potential as a clinical renal imaging agent in humans.