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【目的】评价磁共振体素不相干运动(IVIM)成像定量测量正常妊娠胎盘血流灌注的价值。探讨正常中晚孕期胎盘血液灌注的变化规律。【方法】搜集54例因胎儿轻微先天性发育异常来进行磁共振检查的妊娠中晚期单胎孕妇,所有孕妇在1.5 T磁共振仪进行胎盘的IVIM-DWI成像来计算灌注分数,并通过彩色多普勒超声测量子宫动脉的搏动指数(PI)。54例孕妇依照不同的孕龄(GA)分为Ⅰ组(GA 24-26周)(n=14)、Ⅱ组(GA 27-33周)(n=25)、Ⅲ组(GA 34-40周)(n=15)。IVIM-DWI采用呼吸触发序列,b值设定为:0,10,30,50,70,100,150,200,500,800,1000 s/mm2。IVIM成像参数图,包括标准扩散系数(D)、灌注分数(f)和灌注扩散系数(D*)图通过PRIDE DWI tool软件选择双指数模式自动生成,2名医师分别使用Image J图像处理软件对IVIM的3个参数进行测量。利用组间相关系数(ICC)对观察者间一致性进行判断。3组间D、D*、f的比较采用单因素方差分析,采用线性回归分析灌注分数f与孕龄及子宫动脉搏动指数(PI)的相关性,计算Pearson相关系数。【结果】f(ICC=0.808,P<0.001)与D(ICC=0.881,P<0.001)都有良好的可重复性;D*(ICC=0.754,P<0.001)可重复性一般。单因素ANOVA方差分析结果显示不同孕龄组间f值(33.81±2.94),(29.41±2.70),(27.71±1.53)%的差异有统计学意义(P=0.000),D、D*值在3组间差异无统计学意义,三组孕周的D值分别为:(1.28±0.12)×10~(-3),(1.32±0.14)×10~(-3),(1.27±0.15)×10~(-3)mm2/s(P=0.591);D*值分别为:(80.82±9.86)×10~(-3),(81.33±12.55)×10~(-3),(81.28±10.30)×10~(-3)mm2/s(P=0.982)。f值与孕周呈显著负相关(r=-0.534,P<0.01)。妊娠中晚孕期子宫动脉PI的中位值为0.74,f值与子宫动脉PI值显著相关(r=0.833,P<0.05)。【结论】基于IVIM的灌注分数f值可以作为稳定可信的客观指标量化评价胎盘血流灌注,为不能使用磁共振造影剂的妊娠期妇女评价胎盘血液灌注提供了新的选择。f值与彩色多普勒子宫动脉PI值显著相关,正常妊娠中晚期胎盘灌注分数f值随孕周增加呈下降趋势。
【Objective】 To evaluate the value of quantitatively measuring placental perfusion in normal pregnancy by magnetic resonance voxelin inactivity (IVIM) imaging. To investigate the changes of placental blood perfusion in normal middle and late pregnancy. 【Methods】 54 cases of singleton pregnancies in the second trimester of pregnancy were collected from 54 cases of mild congenital abnormalities of the fetus. All pregnant women underwent IVIM-DWI imaging of the placenta at 1.5 T magnetic resonance to calculate the perfusion score. Pulmonary ultrasound measured pulsatility index (PI) of the uterine artery. 54 pregnant women were divided into group Ⅰ (GA 24-26 weeks) (GA = 14), group Ⅱ (GA 27-33) (n = 25), group Ⅲ (GA 34-40 Week) (n = 15). IVIM-DWI uses respiratory trigger sequence with b values set to: 0, 10, 30, 50, 70, 100, 150, 200, 500, 800, 1000 s / mm2. IVIM imaging parameters including standard diffusion coefficient (D), perfusion fraction (f), and perfusion diffusion coefficient (D *) were generated automatically using the double exponential model using the PRIDE DWI tool software and two physicians used Image J Image Processing Software The three parameters of IVIM are measured. Interobserver agreement (ICC) was used to judge interobserver agreement. Three groups of D, D *, f were compared using one-way ANOVA, linear regression analysis of perfusion score f and gestational age and uterine artery pulse index (PI) correlation calculated Pearson correlation coefficient. 【Results】 The results showed good reproducibility of f (ICC = 0.808, P <0.001) and D (ICC = 0.881, P <0.001). The results of one-way ANOVA analysis showed that there was significant difference (f = 0.000) between f values (33.81 ± 2.94), (29.41 ± 2.70) and (27.71 ± 1.53)% in different gestational age groups There were no significant differences among the three groups (P> 0.05). The values of gestational age in the three groups were (1.28 ± 0.12) × 10 -3, (1.32 ± 0.14) × 10 -3, (1.27 ± 0.15) × 10 -3 mm 2 / s (P = 0.591). The values of D * were (80.82 ± 9.86) × 10 -3, (81.33 ± 12.55) × 10 -3, (81.28 ± 10.30) × 10 ~ (-3) mm2 / s (P = 0.982). The value of f was negatively correlated with gestational age (r = -0.534, P <0.01). Median uterine artery in the second trimester pregnancy PI was 0.74, f value was significantly correlated with uterine artery PI (r = 0.833, P <0.05). 【Conclusion】 IVIM-based perfusion score f can be used as a reliable and reliable objective quantitative evaluation of placental perfusion, providing a new option for the evaluation of placental blood perfusion for pregnant women who can not use magnetic resonance imaging contrast agent. f value and color Doppler uterine artery PI value was significantly correlated with normal late pregnancy placental perfusion score f decreased with gestational age decreased.