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 (Ct) in each transverse section of the kidney. The arterial concentration (Ca) of 82Rb was measured by well counting of arterial blood samples during the equilibrium scan. 82Rb renal uptake (Ct/Ca) 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 X min-1 X 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 X min-1 X 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 X min-1 X 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 X min-1 X g-1 (63%) and 2.92 +/- 0.89 (61%) during mild and severe flow reductions, respectively. We conclude that PET with 82Rb permits serial quantitative assessment of renal flood flow.
Steady-State Predictions from a Compact Cooperative Kinetic Model of Cardiac Sarcomere Dynamics
