THE DETECTION OF THE DYNAMIC RENAL FUNCTION USING MRI BY GADOLINIUM-DTPA

The mathematical study of dynamic renal function and the simulation of renal disorder in rabbit kidney using MRI by Gd-DTPA were performed. T1 of rabbit kidney, which had been operated (complete unilateral ureteral occulusion or incomplete unilateral occlusion of renal artery) was calculated before and after intravenous injection of 0.05mmol/kg Gd-DTPA, continuously for 90 minutes. All images were obtained by the 0.1 Tesla resistive type MRI. The changes of 1/T1 of cortex and medulla of both kidneys were calculated (MRI renogram). The 4 compartment model of bilateral kidneys was established by 6 normal MRI renogram and renal blood flow-glommelurar function parameter and tubural excration function parameter were calculated by the Runge-Kutta-Gill method and the nonlinear least squares method (Simplex method). The change of renogram pattern was observed by the mathematical change of such parameters and comparative study was performed between such mathematical simulation and practical cases. The actual change of such parameters were calculated by the experimental model of rabbit kidney. It was concluded that the change of MRI renogram pattern was sensitive for unilateral hydronephrosis, renal parenchymal dysfunction by obstructive uropathy and unilateral renal arterial stenosis. Quantitative observation of focal renal parenchymal dysfunction, which was induced by ureteral obstruciton, was possible. In the near future it will be also possible to detect acculate ERBF and GFR by the mesurement of T1 of human kidney.