Purpose: Renal function can be quantified by both laboratory and scintigraphic methods. In the case of small animal diagnostics, scintigraphic image-based methods are ideal since they can assess split renal function, work noninvasively, and can be repeated. The aim of this study is to validate a (18)F-PET-based method to quantify renal function in rats.
Materials and methods: Fluoride clearance was calculated from a dynamic whole body listmode acquisition of 60 min length in a small animal PET scanner following an i.v. injection of 15 MBq (18)F-fluoride. Volumes of interest (VOIs) were placed in the left ventricle and the bladder as well as traced around the kidney contours. The respective time-activity curves (TAC) were calculated. The renal (18)F-clearance was calculated by the ratio of the total renal excreted activity (bladder VOI) and the integral of the blood TAC. PET-derived renal function was validated by intraindividual measurements of creatinine clearance (n = 23), urea clearance (n = 23), and tubular excretion rate (TER-MAG3). The split renal function was derived from the injection of the clinically available radionuclide (99m)Tc-mercaptotriglycine by blood sampling and planar renography (n = 8).
Results: In all animals studied, PET revealed high-quality TACs. PET-derived renal fluoride clearance was linearly correlated with intraindividual laboratory measures (PET vs. creatinine: r = 0.78; PET vs. urea: r = 0.73; PET vs. TER-MAG3: r = 0.73). Split function was comparable ((18)F-PET vs. MAG3-renography: r = 0.98). PET-derived measures were highly reproducible.
Conclusions: (18)F-PET is able to noninvasively assess renal function in rats and provides a significant potential for serial studies in different experimental scenarios.