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

Abstract

A study of the dynamic renal function in rabbits using MRI by Gd-DTPA was performed. T1 of rabbit kidney, which had been operated (complete unilateral ureteral occlusion or incomplete unilateral occulusion of the renal artery) was calculated before and after intravenous injection of 0.05mmol/kg of 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 plotted (MRI renography).
T1 of renal cortex was shorter than that of renal medulla in normal kidney by plain T1 image, and T1 of both parts of the kidney was elongated day after day in unilateral hydronephrotis without contrast media. The peak was marked 2 minutes after injection of Gd-DTPA and the half-life of the excretory phase was 30 minute in the cortex and 40 minute in the medulla in normal MRI renography.
The operated site was higher than the opposite-site in the change of 1/T1 (the peak value—the value before administration) immediately after operation, but after 24 hours the operated site was lower, in hydronephrotic rabbits. The renal parenchymal damage due to ureteral obstruction was accurately and sensitively detected. In renal arterial stenosis, the change of 1/T1 was minimal in the operated-site because of the reduction of excretion of contrast media due to decrease of GFR.
It was concluded that MRI renography was able to detect regional dynamic renal function and it was expected that calculation of ERBF, GFR and tubular excretory function was quantitively examined by mathematical analysis.