Department of Pathology, Aalborg University Hospital, Ladegaardsgade 3, 9000, Aalborg, Denmark.
Department of Obstetrics and Gynecology, Aalborg University Hospital, Reberbansgade 15, 9000, Aalborg, Denmark; Department of Clinical Medicine, Aalborg University, Sdr. Skovvej 15, 9000, Aalborg, Denmark.
Placenta. 2020 Feb;91:52-58. doi: 10.1016/j.placenta.2020.01.009. Epub 2020 Jan 23.
Our aim was to assess placental function by diffusion-weighted magnetic resonance imaging (MRI) using intravoxel incoherent motion (IVIM) analysis in uncomplicated pregnancies and pregnancies complicated by placental dysfunction.
31 normal pregnancies and 9 pregnancies complicated by placental dysfunction (birthweight ≤ -2SD and histological signs of placental vascular malperfusion) were retrieved from our placental MRI research database. MRI was performed at gestational weeks 20.1-40.6 in a 1.5 T system using 10 b-values (0-1000 s/mm). Regions of interest were drawn covering the entire placenta in five transverse slices. Diffusion coefficient (D), pseudodiffusion coefficient (D*) and perfusion fraction (f) were estimated by IVIM analysis.
In normal pregnancies, placental f decreased linearly with gestational age (r = -0.522, p = 0.002) being 26.2% at week 20 and 18.8% at week 40. D and D* were 1.57 ± 0.03 and 31.7 ± 3.1 mm/s (mean ± SD), respectively, and they were not correlated with gestational age. In complicated pregnancies, f was significantly reduced (mean Z-score = -1.16; p = 0.02) when compared to the group of normal pregnancies, whereas D and D* did not differ significantly between groups. Subgroup analysis demonstrated that f was predominantly reduced in dysfunctional placentas characterized by fetal vascular malperfusion (mean Z-score = -2.11, p < 0.001) rather than maternal vascular malperfusion (mean Z-score = -0.40, p = 0.42). In addition, f was negatively correlated with uterine artery pulsatility index (r = -0.396, p = 0.01).
Among parameters obtained by the IVIM analysis, only f revealed significant differences between the normal and the dysfunctional placentas. Subgroup analysis suggests that placental f may be able to discriminate non-invasively between different histological types of vascular malperfusion.
本研究旨在通过扩散加权磁共振成像（DWI）的体素内不相干运动（IVIM）分析，评估正常妊娠及胎盘功能障碍妊娠（新生儿体重低于-2SD 和胎盘血管灌注不良的组织学特征）的胎盘功能。
从我们的胎盘 MRI 研究数据库中检索到 31 例正常妊娠和 9 例胎盘功能障碍妊娠（新生儿体重低于-2SD 和胎盘血管灌注不良的组织学特征）。在 1.5T 系统上，在妊娠 20.1-40.6 周进行 MRI 检查，使用 10 个 b 值（0-1000s/mm）。在 5 个横断面上，在整个胎盘上绘制感兴趣区。通过 IVIM 分析估算扩散系数（D）、假性扩散系数（D*）和灌注分数（f）。
在正常妊娠中，胎盘 f 值随孕周呈线性下降（r=-0.522，p=0.002），在 20 周时为 26.2%，在 40 周时为 18.8%。D 和 D分别为 1.57±0.03 和 31.7±3.1mm/s（平均值±标准差），与孕周无相关性。在复杂妊娠中，与正常妊娠组相比，f 值显著降低（平均 Z 评分=-1.16；p=0.02），而 D 和 D在两组间无显著差异。亚组分析表明，f 值主要在胎儿血管灌注不良的功能失调胎盘中降低（平均 Z 评分=-2.11，p<0.001），而不是在母体血管灌注不良的胎盘中降低（平均 Z 评分=-0.40，p=0.42）。此外，f 值与子宫动脉搏动指数呈负相关（r=-0.396，p=0.01）。
在 IVIM 分析获得的参数中，只有 f 值在正常和功能失调胎盘之间有显著差异。亚组分析表明，胎盘 f 值可能能够无创地区分不同类型的血管灌注不良。
