Shear wave elastography of placenta: in vivo quantitation of placental elasticity in preeclampsia

Abstract

Purpose: We aimed to evaluate the utility of shear wave elastography (SWE) for assessing the placenta in preeclampsia disease.

Methods: A total of 50 pregnant women in the second or third trimester (23 preeclampsia patients and 27 healthy control subjects) were enrolled in the study. Obstetrical grayscale and Doppler ultrasonography, SWE findings of placenta, and prenatal/postnatal clinical data were analyzed and the best SWE cutoff value which represents the diagnosis of preeclampsia was determined. Sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), and diagnostic accuracy of preeclampsia were calculated based on SWE measurements.

Results: Mean stiffness values were much higher in preeclamptic placentas in all regions and layers than in normal controls. The most significant difference was observed in the central placental area facing the fetus where the umbilical cord inserts, with a median of 21 kPa (range, 3-71 kPa) for preeclampsia and 4 kPa (range, 1.5-14 kPa) for the control group (P < 0.01). The SWE data showed a moderate correlation with the uterine artery resistivity and pulsatility indices. The cutoff value maximizing the accuracy of diagnosis was 7.35 kPa (area under curve, 0.895; 95% confidence interval, 0.791-0.998); sensitivity, specificity, PPV, NPV, and accuracy were 90%, 86%, 82%, 92%, and 88%, respectively.

Conclusion: Stiffness of the placenta is significantly higher in patients with preeclampsia. SWE appears to be an assistive diagnostic technique for placenta evaluation in preeclampsia.

Figure 1. a, b.

Shear wave elastography (SWE) images of placenta in pregnant women with and without preeclampsia. The sagittal imaging plane (a) shows the placenta of a 23-year-old pregnant woman in the 32^nd week of gestation with no findings of preeclampsia. Two split US and shear wave elastography images are at the same level. The rectangular box represents the stiffness in blue and ROI is placed in the denser area. Mean and maximum elasticity was measured as 5.7 kPa and 9.8 kPa, respectively. Panel (b) shows the SWE image of a 30-year-old preeclampsia patient in the 28^th week of gestation. The rectangular box represents the stiffness spectrum in blue to red. ROI is placed in peak stiffness area which is represented in red. Mean and maximum elasticity was measured as 56.2 kPa and 63.2 kPa, respectively.

Figure 2.

The receiver operating characteristic (ROC) curve for median stiffness value at the central fetal surface of the placenta (n=50).