中晚孕期胎儿脑室及后颅窝池发育的磁共振成像定量分析

Quantitative study on the development of fetal ventricles and cisterna magna in second and third trimesters with MRI

目的分析中晚孕期正常胎儿脑室和后颅窝池生长发育随孕周的变化规律及与胎儿性别的相关性,并制定磁共振(MR)产前诊断参考标准。方法回顾性分析2012年6月至2017年8月在复旦大学附属妇产科医院影像科行磁共振成像(MRI)检查无中枢神经系统异常的胎儿共633例,平均孕周18.9~40.6(27.0±4.1)周。在MRI图像标准层面测量胎儿侧脑室三角区宽度(LVTW)、第三脑室宽度(TVW)、第四脑室宽度(FVW)、第四脑室前后径(APDFV)、透明隔间腔宽度(CSPW)以及小脑延髓池宽度(CMW)。分析各指标与孕周及胎儿性别的相关性,并计算各指标正常参考值。各指标与胎儿性别的相关性采用Spearman相关分析,与孕周的相关性采用Pearson相关分析,与孕周高度相关性指标进一步行回归分析,男女胎儿组间各测量指标及孕周均值比较采用两独立样本t检验,左、右侧脑室宽度(LLVTW、RLVTW)均值比较采用配对样本t检验。结果(1)中晚孕期胎儿LLVTW、RLVTW、TVW、CSPW及CMW分别与孕周呈中、低度相关(相关系数r值分别0.311、0.277、0.207、0.226、0.295,均P<0.01);FVW及APDFV均与孕周显著线性相关(r=0.802、0.831,均P=0.000),线性回归方程分别为:y=0.022×孕周-0.043(调整R2=0.642);y=0.018×孕周-0.159(调整R2=0.690)。(2)LLVTW、RLVTW、FVW、APDFV、CSPW均与胎儿性别不相关(r=-0.078、-0.057、-0.087、-0.004、0.024,P=0.124、0.258、0.085、0.931、0.618,均P>0.05);TVW、CMW与胎儿性别相关(r=-0.310、-0.180,P=0.000、0.006,均P<0.05)。(3)LLVTW、RLVTW均值分别为(0.71±0.13)cm、(0.68±0.13)cm,两者差异有统计学意义(t=3.180,P=0.002);CSPW均值为(0.59±0.15)cm,TVW及CMW男、女胎儿均值分别为:(0.17±0.05)cm、(0.16±0.06)cm和(0.68±0.15)cm、(0.58±0.15)cm。相应MRI产前诊断标准分别为:LLVTW1.1cm,RLVTW1.0cm,CSPW1.0cm,TVW0.3cm,CMW(男1.1cm,女1.0cm)。结论中晚孕期正常胎儿脑室及后颅窝池均随孕周增加表现出不同程度增长趋势,TVW及CMW与胎儿性别相关。依据孕周及胎儿性别间差异分别制定脑室及后颅窝池的正常参考值,可为MRI产前诊断提供准确参考。

Objective To analyze the changes of growth and development of normal fetal ventricles and cisterna magna with gestational age(GA) and the correlation with fetal gender in the second and third trimester,and establish the MR prenatal diagnosis reference standards. Methods A total of 633 fetuses (mean GA (27.0±4.1) weeks (18.9-40.6 weeks))without central nervous system abnormalities were retrospectively collected from the Obstetrics and Gynecology Hospital of Fudan University from June 2012 to August 2017. The lateral ventricle trigonometric width (LVTW), third ventricle width (TVW), fourth ventricle width (FVW), anterior-posterior diameter of the fourth ventricle(APDFV), cavum septum pellucidum width (CSPW) and cisterna magna width (CMW) were obtained in the standard measure planes on MR image.The correlation between the biometrics and GA and the correlation between the biometrics and fetal gender were analyzed respectively, and the normal reference values of the biometrics were calculated. Spearman correlation analysis, Pearson correlation analysis,linear regression analysis, independent samples t-test and paired samples t-test were used for statistic analysis. Results (1)Fetal LLVTW,RLVTW,TVW,CSPW and CMW in second and third trimesters were correlated with GA at medium and low levels(the correlation coefficient r were 0.311, 0.277, 0.207, 0.226, 0.295, respectively, all P<0.01). FVW and APDFV were statistically correlated with GA, and the linear regression equations were as follows: y=0.022×GA-0.043 (adjusted R2=0.642);y=0.018×GA-0.159 (adjusted R2=0.690).(2)Fetal LLVTW,RLVTW,FVW,APDFV and CSPW were not correlated with fetal gender in second and third trimesters(r=-0.078,-0.057,-0.087,-0.004 and 0.024, P=0.124,0.258,0.085,0.931 and 0.618, all P>0.05). TVW and CMW were statistically correlated with fetal gender(r=-0.310,-0.180, P=0.000, 0.006, all P<0.05).(3) The mean values of LLVTW and RLVTW were (0.71±0.13) cm and (0.68±0.13) cm, respectively, and significant difference was found between them(t=3.180, P=0.002). The mean value of CSPW was (0.59±0.15) cm. And the mean values of male and female fetuses for TVW and CMW were (0.17±0.05) cm,(0.16±0.06) cm and (0.68±0.15) cm,(0.58±0.15) cm, respectively. The corresponding prenatal MRI diagnostic criteria were as follows: LLVTW 1.1 cm, RLVTW 1.0 cm, CSPW 1.0 cm, TVW 0.3 cm, CMW (male 1.1 cm, female 1.0 cm). Conclusions The normal fetal ventricles and cisterna magna are increased with the GA in the second and third trimesters. TVW and CMW are related to fetal gender. The establishment of normal reference values of fetal ventricles and cisterna magna based on GA and fetal gender are conducive to enhance the accuracy of MRI prenatal diagnosis.