体素内不相干运动序列定量评估孕中晚期胎盘弥散及灌注的研究

Quantitative Assessment of Placental Diffusion and Perfusion in Second and Third Trimester by Intravoxel Incoherent Motion

目的探讨不使用对比剂的情况下采用体素内不相干运动(IVIM)序列定量测量正常胎盘孕中晚期血流灌注及弥散情况的可行性,以及其与孕周的相关性。资料与方法纳入43例超声检查显示胎儿畸形并行MRI检查的单胎妊娠孕妇,所有孕妇均在行超声检查72 h内行MRI检查,常规MRI形态学序列T2 HASTE和T1WI压脂序列扫描后行IVIM扫描。剔除图像伪影较重或变形明显的3例。由2名MRI阅片医师分别测量40例胎盘快速表观扩散系数(D)、慢速表观扩散系数(D*)、快速扩散所占容积分数(f),并评价一致性;分析其与孕周之间的关系。结果一致性分析结果显示,2名医师测量D值(ICC=0.814,P<0.05)和f值(ICC=0.911,P<0.05)一致性良好,D*值的一致性一般(ICC=0.746,P<0.05)。对于正常妊娠的胎盘,孕中晚期f值为(35.81±8.84)%,与孕周呈负相关(r=-0.491,P=0.003);D^*值为(90.67±27.14)×10^-3 mm^2/s,与孕周呈负相关(r=-0.380,P=0.027);D值为(1.36±0.16)×10^-3 mm^2/s,与孕周无相关性(r=0.076,P=0.314)。孕中晚期孕妇侧胎盘的f值为(42.12±8.79)%,胎儿侧为(32.76±11.12)%,两者差异有统计学意义(t=2.093,P<0.05)。结论IVIM序列测得孕中晚期孕妇正常胎盘的D、f值用于评价胎盘弥散及血流灌注具有一定的可行性。f值和D*值均与孕周呈负相关,可用于孕妇胎盘血流灌注评价。

Purpose To explore the feasibility of using intravoxel incoherent motion(IVIM)sequence to quantitatively measure the blood perfusion and diffusion of normal placenta in the second and third trimesters of pregnancy,and to explore its correlation with gestational age.Materials and Methods Forty-three pregnant women with singleton pregnancy who showed fetal malformation and MRI examination were included in the study.Placenta MRI was performed within 3 days after US examinations.All cases were examined with routine fetal MRI protocol,including HASTE and T1-weighted sequences(fat saturation),and then IVIM sequence.For the 43 cases,3 cases with severe artifacts or obvious deformations were excluded,and the remaining 40 placentas were measured with D,D*,f values and the data was analyzed.The reproducibility of D,D*,f value was calculated,and the correlation between these three parameters and gestational age was analyzed.Results The reproducibility of D value(ICC=0.814,P<0.05)and f value(ICC=0.911,P<0.05)was good,but the reproducibility of D*was general(ICC=0.746,P<0.05).For the placenta of normal pregnancy,the mean f value in the second and third trimesters of pregnancy was(35.81±8.84)%,f value was negatively correlated with gestational age(r=-0.491,P=0.003).The D^*value was(90.67±27.14)×10^-3 mm^2/s,which was negatively correlated with gestational age(r=-0.380,P=0.027);D value was(1.36±0.16)×10^-3mm^2/s,no correlation with gestational age(r=0.076,P=0.314).The f value of the placenta on the side of the pregnant woman in the second and third trimesters was(42.12±8.79)%and that on the fetal side was(32.76±11.12)%,the difference between the two was statistically significant(t=2.093,P<0.05).Conclusion The D and f values of the normal human placenta in the middle and late stages have certain feasibility for evaluating placental diffusion and blood perfusion.Both f and D*values are negatively correlated with gestational age,and can be used to evaluate placental blood flow perfusion in pregnant women.