Functional MRI of Transplanted Kidneys using Diffusion-Weighted Imaging

Purpose: Contrast-enhanced MRI is considered problematic in renal allograft recipients due to the association of gadolinium administration and the development of NSF. Therefore, we assessed the clinical value of mono- and biexponential analysis of diffusion-weighted imaging (DWI). Materials and Methods: A total of 32 patients were divided into four groups: (a) patients with stable function of renal allograft for at least 6 months, (b) patients with acute deterioration of allograft function, patients who recently underwent transplantation (< 14 days) with good (c) or decreased (d) renal function. T2w ax. and T1w cor. and a diffusion-weighted sequence with 16 b-values (b = 0 - 750 s/mm(2)) were performed on a 1.5 T scanner (Magnetom Avanto, Siemens Medical Solutions). ROI-based analysis of the renal cortex was analyzed using the software "Table Curve 2D". Results: Monoexponential analysis showed an ADC(mono) of 1961 +/- 104 1801 +/- 150, 2053 +/- 169 and 1720 +/- 191 10-6mm(2)/sec for patient group a, b, c and d respectively. The difference in ADC(mono) between group (a) and (b) (p < 0.006) and between group (c) and (d) (p < 0.04) was statistically significant. Biexponential analysis revealed a mean perfusion fraction of 0.21, 0.23, 0.32 and 0.24 for group (a), (b), (c) and (d), respectively. Biexponential ADC showed a higher numerical accuracy. There were no statistically significant inter-group differences in diffusion (ADC(D)) and perfusion (ADC(P)). Conclusion: Unenhanced evaluation of renal allografts with DWI is feasible. ADC(mono) of renal cortex correlates with renal function. The significance of the higher numerical accuracy of biexponential analysis in clinical settings requires further evaluation in larger-scale studies.