Renal Artery Stenosis: Functional Assessment with Dynamic MR Perfusion Measurements—Feasibility Study

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Abstract
To prospectively assess feasibility of renal magnetic resonance (MR) perfusion measurement method based on turbo fast low-angle shot sequences for grading effect of renal artery stenosis (RAS) on parenchymal perfusion. Institutional review board approved this study, and patients gave written consent. Seventy-three patients (34 male, 39 female; age range, 17-84 years) who were clinically suspected of having RAS underwent contrast material-enhanced (gadodiamide) saturation-recovery turbo fast low-angle shot imaging for measurement of renal perfusion and high-spatial-resolution MR angiography for RAS detection and grading. Degree of stenosis was evaluated as high grade (>/=75% stenosis), low to intermediate grade (>0% to <75% stenosis), or absent. High temporal resolution of the turbo fast low-angle shot sequence allowed acquisition of an exact first-pass tracing of the contrast agent bolus from which a signal intensity (SI)-time curve was derived. On the basis of this curve, mean transit time (MTT) of the contrast agent bolus, maximal upslope (MUS) of the curve, maximum SI, and time to SI peak (TTP) were calculated with a gamma variate fit. Wilcoxon rank sum test, Pearson product moment correlation, and paired t test were used for statistical analysis. Twenty-four renal arteries had high-grade RAS, 12 renal arteries had low- to intermediate-grade RAS, and 104 renal arteries had no RAS. Significant differences between patients without stenoses or with low- to intermediate-grade stenoses and patients with high-grade stenoses were found for MTT, MUS, and TTP (P < .001). Perfusion parameters were correlated with patients' serum creatinine levels, and significant correlations were found for MTT (r = 0.41), MUS (r = 0.48), and TTP (r = 0.4), with P < .001. MR perfusion parameters can be used to assess effect of RAS on parenchymal perfusion. Perfusion measurements reflect renal function as measured with serum creatinine levels.