Aims: To determine the inter-patient variability of apparent diffusion coefficients (ADC) and concurrent micro-circulation contributions from diffusion-weighted MR imaging (DW-MRI) in renal allografts early after transplantation, and to obtain initial information on whether these measures are altered in histologically proven acute allograft rejection (AR).
Methods: DW-MRI was performed in 15 renal allograft recipients 5-19 days after transplantation. Four patients presented with AR and one with acute tubular necrosis (ATN). Total ADC (ADC(T)) was determined, which includes diffusion and micro-circulation contributions. Furthermore, diffusion and micro-circulation contributions were separated, yielding the "perfusion fraction" (F(P)), and "perfusion-free" diffusion (ADC(D)).
Results: Diffusion parameters in the ten allografts with stable function early after transplantation demonstrated low variabilities. Values for ADC(T) and ADC(D) were (x10(-5) mm(2)/s) 228 +/- 14 and 203 +/- 9, respectively, in cortex and 226 +/- 16 and 199 +/- 9, respectively, in medulla. F(P) values were 18 +/- 5% in cortex and 19 +/- 5% in medulla. F(P) values were strongly reduced to less than 12% in cortex and medulla of renal transplants with AR and ATN. F(P) values correlated with creatinine clearance.
Conclusion: DW-MRI allows reliable determination of diffusion and micro-circulation contributions in renal allografts shortly after transplantation; deviations in AR indicate potential clinical utility of this method to non-invasively monitor derangements in renal allografts.