3D MR结肠成像评价孕中晚期胎儿结直肠发育

3D MR colonography for evaluating fetal colorectal development in the second and the third trimester of pregnancy

目的观察3D MR结肠成像(3D MRC)评估孕中晚期胎儿结直肠发育的价值。方法回顾性分析83胎经出生后随访或尸检证实胃肠道正常胎儿[孕中期21胎(13~27+6周)、孕晚期62胎(≥28周且<31+6周34胎、≥32周28胎)]胎儿MRI,包括真实稳态进动快速成像(true-FISP)T2WI、半傅立叶单次激发快速自旋回波(HASTE)T2WI及二维快速小角度激发梯度回波(2D FLASH)TIWI;基于2D FLASH T1WI重建获得3D MRC,分析不同胎龄胎儿正常结直肠信号,测量各段结肠及直肠最宽处平均宽度,分析其与胎龄的相关性,建立线性回归方程。结果随胎龄增加,2D FLASH T1WI显示胎儿结直肠表现为高信号,HASTE T2WI呈明显低信号。3D MRC显示,随胎龄增加,胎儿结直肠内的胎粪自远段至近段结肠逐渐蓄积,呈管腔内较连续、均匀分布的高信号,旋转图像可显示肠道收缩、纡曲及折叠部分。胎儿正常结直肠平均宽度为(8.38±2.96)mm,且随孕周增加而逐渐增大,回归方程为Y(结直肠平均宽度)=-8.39+0.559X(胎龄),R^(2)=0.81。结论3D MRC有助于评估胎儿结直肠发育。

Objective To investigate the value of 3D MR colonography(MRC)for evaluating fetal colorectal development in the second and the third trimester of pregnancy.Methods Data of fetal MRI,including true fast imaging with steady-state precession(true-FISP)T2WI,half-Fourier acquired single shot turbo spin-echo(HASTE)T2WI and 2D fast low angle shot(2D FLASH)T1WI of 83 fetuses(21 fetuses in the second pregnancy[13—27+6 weeks]and 62 in the third pregnancy[34 fetuses≥28 weeks and<31+6 weeks,28 fetuses≥32 weeks])with normal gastrointestinal tract confirmed by postnatal following-up or autopsy were retrospectively analyzed.3D MRC was obtained based on reconstruction of 2D FLASH T1WI.Normal colorectal signals of fetuses in different gestational ages were observed,and the average diameter of each segment of colon as well as the width at the widest part of the rectum were measured,and the correlation of the width with gestational ages were analyzed,then the linear regression model was established.Results With the increase of gestational age,2D FLASH T1IW showed high signals,and HASTE T2WI showed significant low signals in the fetal colorectums.3D MRC showed that fetal meconium accumulated gradually from distal to proximal colon with gestational age,presenting as relatively continuous and uniform distribution of high signal within the lumen.Rotating images could show constricted,tortuous and folded intestine.The average width of fetal normal colorectums was(8.38±2.96)mm,which gradually increased with gestational age,and the regression equation was Y(the average width of fetal normal colorectums)=-8.39+0.559 X(gestational age),R^(2)=0.81.Conclusion 3D MRC could help to assess fetal colorectal development.