功能磁共振评估宫内发育迟缓仔鼠肾脏微观结构及灌注改变

Functional MRI assessment of microstructural and perfusion changes in the kidneys of rats with intrauterine growth restriction

摘要:

目的 探讨体素内不相干运动（intravoxel incoherent motion, IVIM）、纵向弛豫时间定量成像（T1 mapping）、横向弛豫时间定量成像（T2 mapping）等功能磁共振成像技术评估宫内发育迟缓（intrauterine growth restriction, IUGR）仔鼠的肾脏微观结构及灌注改变的价值。方法 通过孕期低蛋白饮食法建立IUGR仔鼠模型。低蛋白饮食孕鼠所产仔鼠随机分为IUGR 8周组、IUGR 12周组，正常饮食孕鼠所产仔鼠随机分为正常8周组、正常12周组，各组n=8。比较各组仔鼠肾脏皮质、髓质的表观弥散系数（apparent diffusion coefficient, ADC）、真实扩散系数（D_t）、伪扩散系数（D^*）、灌注分数（f）、T1值、T2值，以及血肌酐、血尿素氮水平。结果 IUGR 12周组肾脏髓质D_t值高于IUGR 8周组，IUGR 12周组肾脏髓质D^*值低于正常12周组与IUGR 8周组（P<0.05）；IUGR 8周组肾脏髓质T1值高于皮质，IUGR 12周组肾脏髓质T1值高于IUGR 8周组与正常12周组，IUGR 12周组肾脏皮质T1值高于正常12周组（P<0.05）；各组内肾脏髓质T2值均高于皮质（P<0.05），各组间肾脏皮质及髓质的T2值比较差异均无统计学意义（P>0.05）。各组血肌酐及血尿素氮含量比较差异无统计学意义（P>0.05）。IUGR 8周组仔鼠肾脏可见肾小球增生肥大，未见明显纤维化改变；IUGR 12周组仔鼠肾脏可见肾小球萎缩，囊腔狭窄，间质出现炎性细胞浸润及纤维化。结论 IVIM磁共振成像可用于评估及动态观察IUGR仔鼠肾脏微观结构及灌注损伤，T1 mapping磁共振成像可用于评估IUGR仔鼠肾脏损伤，T1 mapping联合T2 mapping磁共振成像可进一步分辨IUGR仔鼠的肾脏纤维化。

Abstract:

Objective To explore the value of functional magnetic resonance imaging (MRI) techniques, including intravoxel incoherent motion (IVIM), T1 mapping, and T2 mapping, in assessing the microstructural and perfusion changes in the kidneys of rats with intrauterine growth restriction (IUGR).Methods An IUGR rat model was established through a low-protein diet during pregnancy. Offspring from pregnant rats on a low-protein diet were randomly divided into an IUGR 8-week group and an IUGR 12-week group, while offspring from pregnant rats on a normal diet were divided into a normal 8-week group and a normal 12-week group (n=8 for each group). The apparent diffusion coefficient (ADC), true diffusion coefficient (D_t), pseudo-diffusion coefficient (D^*), perfusion fraction (f), T1 value, and T2 value of the renal cortex and medulla were compared, along with serum creatinine and blood urea nitrogen levels among the groups.Results The D_t value in the renal medulla was higher in the IUGR 12-week group than in the IUGR 8-week group, and the D^* value in the renal medulla was lower in the IUGR 12-week group than in both the normal 12-week group and the IUGR 8-week group (P<0.05). The T1 value in the renal medulla was higher than in the cortex in the IUGR 8-week group, and the T1 value in the renal medulla was higher in the IUGR 12-week group than in both the IUGR 8-week group and the normal 12-week group, with the cortical T1 value in the IUGR 12-week group also being higher than that in the normal 12-week group (P<0.05). The T2 values in the renal medulla were higher than those in the cortex across all groups (P<0.05). There were no significant differences in the T2 values of either the cortex or medulla among the groups (P>0.05). There were no significant differences in serum creatinine and blood urea nitrogen levels among the groups (P>0.05). Glomerular hyperplasia and hypertrophy without significant fibrotic changes were observed in the IUGR 8-week group, whereas glomerular atrophy, cystic stenosis, and interstitial inflammatory infiltration and fibrosis were seen in the IUGR 12-week group.Conclusions IVIM MRI can be used to assess and dynamically observe the microstructural and perfusion damage in the kidneys of IUGR rats. MRI T1 mapping can be used to evaluate kidney damage in IUGR rats, and the combination of MRI T1 mapping and T2 mapping can further differentiate renal fibrosis in IUGR rats.