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 microcirculation 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 (×10 −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.

No abstract

DW MR imaging depicts early adaptations in the remaining nontransplanted kidney of donors after nephrectomy. All diffusion parameters remained constant in allograft recipients after transplantation. This method has potential monitoring utility, although assessment of clinical relevance is needed.

Diffusion-weighted MR imaging allows noninvasive detection of changes in renal perfusion and diffusion during acute unilateral ureteral obstruction, as exemplified in patients with a ureteral calculus.

Purpose: To prospectively determine the 3-year stability and potential changes of functional parameters in renal allograft recipients obtained from diffusion-weighted imaging (DWI) and blood oxygenation level-dependent (BOLD) MRI. Materials and Methods:Nine renal allograft recipients underwent DWI and BOLD-MRI twice, once 7 6 3 months after transplantation, and again 32 6 2 months after the first MRI. DWI yielded an apparent diffusion coefficient (ADC) and the perfusion contribution (F P ). BOLD imaging yielded R2*, providing an estimation of renal oxygenation. Coefficients of variation between (CV b ) and within subjects (CV w ) were calculated.Results: The parameters were stable after 32 months in eight of the nine patients, who had well-functioning allografts. Mean diffusion values were very similar in the first and second scan. CV w and CV b for ADC values were less than 3.5% and 5.9%, respectively, in cortex and medulla, but were higher for F P (15%-18%). CV w and CV b of R2* were also low (medulla: CV w ¼ 10.8%, CV b ¼ 11.4%; cortex: CV w and CV b ¼ 7.2%). R2* increased significantly (P ¼ 0.035) in cortex but not in medulla, suggesting reduced cortical oxygen content. One subject with decreased glomerular filtration rate demonstrated strongly altered parameters. Conclusion:In the absence of graft dysfunction, DWI and BOLD imaging yield consistent results over 3 years in stable human renal allograft recipients.