正常大鼠肾脏MR弥散成像与大体解剖的对照研究

Correlation of diffusion-weighted MRI and gross anatomy of rat kidneys

目的通过与大鼠肾脏大体解剖的对照,探讨磁共振扩散加权成像(DWI)对大鼠肾实质各层结构的显示能力。方法在1.5T磁共振成像系统上分别应用平面回波成像(EPI)DWI(选取不同b值)和普通成像序列T_1WI及T_2WI扫描正常大鼠12只,比较各序列显示肾实质层次的特点,并比较不同b值对肾实质的显示情况,测量DWI肾实质各层的厚度,并与大鼠肾脏的大体解剖结构相对照分析。结果大体解剖大鼠肾实质可分为清晰的皮质层(CO)、外髓层外层(OS)、外髓层内层(IS)(OM)及内髓层(the innermedulla,IM)四层结构和肾盂、肾盏等结构。MR不同序列对大鼠肾实质各层结构显示不同:T_1WI显示CO和髓质层(medulla)两层;T_2WI清晰显示CO、OM及IM3层结构;而DWI则能清晰或较清晰显示CO、OS、IS及IM四层结构,ADC图显示更为清楚。DWI对大鼠肾实质结构显示优于T_1WI及T_2WI,其差异具有统计学意义(P<0.05)。大体标本大鼠肾实质各层厚度分别为:CO(1.45±0.09)、OS(1.01±0.25)、IS(1.01±0.14)和IM(1.14±0.11)mm;DWI上各层厚度分别为:CO(1.39±0.15)、OS(1.01±0.17)、IS(1.11±0.19)和IM(1.06±0.10)mm,两者差异无统计学意义(P>0.05)。选取不同b值对肾实质层结构的显示并无影响,不同b值之间的差异无统计学意义(P>0.05)。结论应用1.5T磁共振成像系统DWI所显示大鼠肾实质四层结构与大体解剖结构有较好的一致性。

Objective To investigate the feasibility and accuracy of diffusion-weighted MRI in differentiating the cortico-medullary layers of rat kidneys. Methods Twelve rats underwent MRI using a 1.5 Tesla system including DWI of various b-values, T1WI and T2WI sequences. The MR characteristics and thickness of renal cortico-medullary layers were compared to those of the gross anatomical layers. Results On the longitudinal anatomical sections of the kidneys, four parenchymal layers of cortex （CO）, the outer （OS） and inner （IS） stripes of the outer medulla （OM）, the inner medulla （IM） and renal pelvis could be clearly recognized. The numbers of layers visible on MRI varied with different pulse sequences. Single layers of cortex and medulla were visible on T,WI. CO, OM and IM were delineated on T2WI. CO, OS, IS and IM were clearly identified on DWI and ADC maps. DWI was significantly superior to T,WI and T2WI for displaying the renal parenchymal layers （P〈0.05）. The thickness of renal parencbyma/layers measured on gross anatomy （CO： 1.45±0.09 mm, OS： 1.01±0.25 mm, IS： 1.01±0.14 ram, IM： 1.14±0.1 lmm） was not significantly different （P〉0.05）from the measurements on DWI （C0：1.39±0.15 mm, OS： 1.01±0.17mm, IS： 1.11±0.19 mm, IM： 1.06±0.10 mm）. Different b-values of DWI did not show significant difference in depiction of the parenchyma（P〉 0.05 ）. Conclusion Four parenehymal layers shown on DWI correlated well with gross anatomical structure and may be used in imaging study of rat kidneys.