Fig. 4.

Measured double-injection MRR data and model fits for a representative kidney. A: tracer concentrations measured from an aortic region of interest. B: tracer retention in cortex is represented by squares and that from medulla by circles. The first-injection data (0–10 min) were fitted using the model described by equations 3-5 (solid lines), with results GFR₁ = 43.8 ml/min, RPF₁ = 208.4 ml/min. The second-injection data (20–30 min) were fitted using the model described in equations 3 and 6 (dashed lines), with results GFR₂ = 44.9 ml/min, RPF₂ = 177.6 ml/min. In this case, GFR₂ − GFR₁ = 1.1 ml/min, while RPF₂ − RPF₁ = −30.8 ml/min. In the absence of renovascular disease, the expected GFR₂ − GFR₁ value is 0.