应用磁共振扩散张量成像评价肾移植术后早期移植肾功能的研究

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

目的探讨磁共振（MR）扩散张量成像（DTI）评价肾移植术后早期移植肾功能的可行性。方法选取51例肾移植术后1个月内的受者及26例健康志愿者，行肾脏斜冠状面3．0T MRDTI检查（扩散梯度方向6，b值为0、300s／mm^2）。依据接受DTIMR检查当天的估算肾小球滤过率（eGFR），将所有受试者分为4组，（1）正常对照组（1组），为正常志愿者26例；（2）eGFR≥60ml·min^-1·1．73m^-2组（2组），24例受者；（3）30ml·min^-1·1．73m^-2≤eGFR〈60ml·min^-1·1．73m^-2组（3组），19例受者；（4）eGFR％30ml·min^-1·1．73m^-2组（4组），8例受者。分别测量和计算各组肾脏皮髓质的ADC值和FA值，并采用配对样本t检验和单因素方差分析进行比较，采用Pearson积差相关分析分析移植肾皮髓质ADC值和FA值与eGFR间相关性。结果各移植组受者间皮质FA值均无明显差异（P〉0．05），但均显著低于1组的皮质FA值（P〈0．01）。随着eGFR的降低，各移植组髓质FA值、ADC值及皮质ADC值均呈递减趋势，且各组间差异均有显著统计学意义（P〈0．05），其中以髓质FA值的差异最为显著。移植肾髓质FA值、ADC值及皮质ADC值与eGFR呈明显正相关（r值分别为0．812、0．756、0．757，P〈0．01）。FA图和ADC图显示，3组与4组移植。肾皮髓质分辨明显减低，扩散张量示踪图显示3组与4组移植肾髓质内纤维束样结构明显稀疏、减少，尤以4组为著。结论DTI评价肾移植术后早期移植肾功能的改变具有可行性，不仅能够定量，而且可以从形态学上有效鉴别处于不同功能状态的移植肾。

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/mm^2 ）. 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 m^2 （n = 24） ; group 3, 30≤eGFR〈60 mL/min/1.73 m^2 （n = 19） ; group 4, eGFR〈30 mL/min/1.73 m^2 （n = 8）. Mean apparent diffusion coefficient （ADC） and mean fractional anisotropy （FA） were determined separately for the cortex and the medulla. The paired Student＇s 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 oneway 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.