扩散MRI评价轻中度孤立性侧脑室扩张胎儿脑白质纤维结构改变的价值

The value of diffusion MRI in assessing structural changes of white matter fibers in fetal brain with mild to moderate isolated ventriculomegaly

目的应用扩散MRI(dMRI)的扩散张量成像(DTI)模型和基于fixel分析(FBA)的方法探讨轻中度孤立性侧脑室扩张(IVM)胎儿脑白质纤维结构的变化情况。方法该研究为病例对照研究,前瞻性纳入2022年8月至2023年8月在山东第一医科大学附属省立医院就诊的轻中度IVM胎儿20例,胎龄为24~36(29.9±3.6)周,为IVM组。对照组纳入22例正常胎儿,来自中国胎儿脑dMRI图谱数据,胎龄为24~36(30.2±3.7)周。所有胎儿均采集dMRI数据,采用DTI模型获得胼胝体膝部、胼胝体压部、小脑中脚,双侧的皮质脊髓束、下纵束、下额枕束、丘脑前辐射7种主要纤维束的各向异性分数(FA)、平均扩散率、轴向扩散率和径向扩散率。采用FBA方法获得全脑纤维密度(FD)、纤维横截面积(FC)和纤维密度与横截面积(FDC)。IVM组与对照组间各纤维束DTI参数的比较采用独立样本t检验或Mann-WhitneyU检验。2组间FBA参数的比较使用协方差分析,使用MRtrix3软件包显示有差异的脑区。结果IVM组与对照组胎儿下纵束的FA值分别为0.142±0.012和0.133±0.015,差异有统计学意义(t=2.21,P=0.033),其余纤维束DTI参数差异均无统计学意义(P>0.05)。全脑FBA结果显示,与对照组比较,IVM组胎儿FD和FC改变的区域主要分布在胼胝体压部、穹隆、矢状层,其中FD降低而FC升高,FDC在皮质脊髓束降低。结论轻中度IVM胎儿存在脑白质纤维微观结构的改变,以位于侧脑室体部、三角区及颞角周围的白质纤维束为主。

Objective To investigate the changes in the white matter fiber structure of fetal brain with mild to moderate isolated ventriculomegaly(IVM)using diffusion tensor imaging(DTI)model and fixed based analysis(FBA)method of diffusion MRI(dMRI).Methods This was a case-control study.Twenty fetuses diagnosed with mild to moderate IVM who were admitted to the Provincial Hospital Affiliated to Shandong First Medical University from August 2022 to August 2023 were included prospectively as the IVM group,with gestational age ranging from 24 to 36(29.9±3.6)weeks.The control group included 22 normal control fetuses obtained from the dMRI atlas data of Chinese fetal brain,with gestational age ranging from 24 to 36(30.2±3.7)weeks.The dMRI data were collected for all fetuses and the DTI model was used to obtain fractional anisotropy(FA),mean diffusivity,axial diffusivity,and radial diffusivity of 7 main fiber bundles,including the genu and splenium of the corpus callosum,middle cerebellar peduncle,bilateral cortico-spinal tract,inferior longitudinal fasciculus,inferior fronto-occipital fasciculus,and anterior thalamic radiation.The FBA method was used to obtain fiber density(FD),fiber cross-sectional area(FC),and fiber density and cross-section(FDC)of the whole brain.The comparison of DTI parameters of each fiber bundle between the two groups was conducted using independent sample t test or Mann-Whitney U test.The comparison of FBA parameters between the two groups was performed using covariance analysis,and the MRtrix3 software package was used to display the brain regions with significant differences.Results The FA values of the inferior longitudinal fasciculus in the IVM group and the control group were 0.142±0.012 and 0.133±0.015,respectively,and the difference was statistically significant(t=2.21,P=0.033),while the DTI parameters of the other fiber bundles showed no statistically significant differences(P>0.05).The whole brain FBA results showed that compared with the control group,FD decreased while FC increased in the corpus callosum,fornix,and sagittal stratum in IVM fetuses,while FDC decreased in the cortico-spinal tract.ConclusionThere are microstructural changes of the brain white matter fiber in intrauterine fetuses with mild to moderate IVM,which are mainly located in the white matter fiber bundles surrounding the body,atrium,and temporal horn of the lateral ventricle.