Evaluation of kidney transplant function early after transplantation with magnetic resonance diffusion tensor imaging

Abstract

Objective To investigate the feasibility of magnetic resonance diffusion tensor imaging (DTI) as a noninvasive way for assessment of kidney transplant function in the early posttransplantation period.Method Fifty-one kidney transplant recipients less than 1 month after kidney transplantation and 26 age-matched healthy volunteers were included and examined using a fatsaturated echo-planar DTI sequence in oblique-coronal orientation at 3.0 Tesla magnetic resonance (MR) imager (diffusion directions=6,b =0,300 s/mm2).According to the estimated glomerular filtration rate (eGFR) recorded and calculated on the examined day,all subjects were divided into four groups:group 1,healthy volunteers (n =26) ; group 2,eGFR≥60 mL/min/1.73 m2 (n =24) ; group 3,30≤eGFR＜60 mL/min/1.73 m2 (n =19) ; group 4,eGFR＜30 mL/min/1.73 m2 (n =8).Mean apparent diffusion coefficient (ADC) and mean fractional anisotropy (FA) were determined separately for the cortex and the medulla.The paired Students t test was used to compare ADC and FA between cortex and medulla within each group.ADC and FA between groups were compared by using the one-way analysis of variance test.Relationship between ADC and FA with eGFR of the transplants was assessed by using Pearson correlation analysis.Result Mean cortical FA was significantly higher in group 1 than in other three groups (P＜0.01 for all),while differences among groups of allograft recipients were not significant (P＞0.05 for all).There was a gradually decreasing trend of medullary FA and ADC,and cortical ADC from group 2 to group 4,and the differences among groups were all pronounced (P＜0.05 for all).In renal allografts,there was a significant positive correlation between eGFR and medullary FA,medullary ADC as well as cortical ADC (r =0.812,0.756,0.757,respectively,P＜0.01).The cortical-medullary discrimination of FA-map and ADC-map in group 3 and group 4 apparently decreased.Meanwhile,DTI revealed that the radial diffusion tracts in the medulla of group 3 and group 4 obviously broke off and reduced,especially in group 4.Conclusion DTI is a promising way to evaluate kidney transplant function early after transplantion,and can quantitatively and visually distinguish transplants with different functions. Key words: Kidney transplantation; Magnetic resonance; Diffusion tensor imaging; Estimated glomerular filtration rate