Purpose: To compare the accuracy of a noninvasive magnetic resonance (MR) imaging method to rapidly determine single-kidney glomerular filtration rate (GFR) relative to findings with an accepted standard of reference.
Materials and methods: Simultaneous inulin and MR imaging measurements of renal excretory function were performed in six small swine. Renal extraction fraction of gadopentetate dimeglumine was determined with T1 measurements of flowing blood in the renal vein and in a systemic vessel 10-300 minutes after administration. These data were correlated with standard inulin-derived measurements of single-kidney GFR obtained during the same intervals as the MR imaging measurements. Gradient-echo (GRE) and echo-planar imaging were investigated for in vivo measurement of extraction fraction.
Results: The MR imaging-derived measurements of extraction fraction and single-kidney GFR were not significantly different from the inulin-determined measures (P > .18). The MR imaging extraction fraction and single-kidney GFR measurements correlated with inulin-derived measurements of the same parameters (r = .74 to .89, P < .0007).
Conclusion: T1 measurement methods with GRE and echo-planar imaging are acceptable techniques with which to measure renal excretory function in a rapid and noninvasive manner in this model. Rapid measurements of single-kidney GFR should enable studies of the response of renal hemodynamics to pharmaceutical manipulation.