Homodyned K-Distribution Temporal-Based Characterization of Rat Placenta Microstructure Using the Reduced Uterine...

We characterize rat placenta microstructure in the context of the reduced uterine perfusion pressure (RUPP) model of preeclampsia using the homodyned K-distribution to parameterize envelope-detected signals of ultrasound radiofrequency echo frames obtained in vivo. Preeclampsia is a life-threatening pregnancy syndrome related to abnormal placental tissue microstructure which motivated the quantitative ultrasound-based tissue characterization approach used in this study.

Ultrasound radiofrequency echo frames against time (or videos) were obtained on 30 and 38 in vivo placentae at gestation day (GD) 14 and 18 respectively, using 9 Sprague-Dawley rats. Preeclampsia-like effects were induced by surgical modification (post GD 14) following the RUPP model, giving a total of 20 RUPP and 18 control placentae at GD 18. The homodyned K-distribution was fit to value distributions of envelope-detected signals of ultrasound radiofrequency echo frames against time, yielding temporal α (scatterer number per resolution cell) and κ (ratio of coherent to diffuse signal power) parameters used to characterize the placental tissue microstructure.

Visualization of GD 18 α values as a color overlay on B-mode ultrasound video suggested higher values of control compared with RUPP. The mean kurtosis for RUPP was 4.07 ± 0.71 in comparison to 5.08 ± 1.28 for the control using placenta-level kurtosis values (p = 0.0044). There were no significant differences observed in GD 14 placentae, consistent with expectations. Further, we visualized and quantified temporal changes in GD 18 α values with frame-level statistics that support earlier findings.

This study quantitatively characterizes rat placenta microstructure using the homodyned K-distribution and temporal α and κ parameters.