Serial analysis of renal blood flow by positron tomography with rubidium-82

To determine whether renal blood flow can be measured by positron-emission tomography (PET) during constant infusion of rubidium-82 (⁸²Rb) using a steady-state kinetic model, studies were performed in 10 dogs at control (n = 10), during mild flow reduction (n = 7), during severe flow reduction (n = 10), and after reperfusion of the kidney (n = 3). PET data were quantified to determine mean concentration of ⁸²Rb (C(t)) in each transverse section of the kidney. The arterial concentration (C(a)) of ⁸²Rb was measured by well counting of arterial blood samples during the equilibrium scan. ⁸²Rb renal uptake (C(t)/C(a)) correlated nonlinearly with microsphere renal blood flow according to a steady-state kinetic model (r = 0.90). ⁸²Rb estimated flow was 3.16 ± 1.36 ml·min^-1·g^-1 at control and 1.56 ± 0.57 and 0.37 ± 0.59 during mild and severe flow reductions, respectively. Microsphere determined flow was 2.89 ± 0.77 ml·min^-1·g^-1 at control, 1.58 ± 0.42 at mild reduction, and 0.27 ± 0.49 at severe reduction. In the occlusion and reperfusion model, the ⁸²Rb estimated flow during occlusion was 0.21 ± 0.15 ml·min^-1·g^-1 and on reperfusion went up to 2.13 ± 1.08. The contralateral kidney demonstrated reductions in the ⁸²Rb estimated flow of 3.02 ± 1.62 ml·min^-1·g^-1 (63%) and 2.92 ± 0.89 (61%) during mild and severe flow reduction, respectively. We conclude that PET with ⁸²Rb permits serial quantitative assessment of renal blood flow.