Comparison of shear wave speed estimates in Ex vivo non-pregnant vs. in vivo pregnant cervix
The cervix is primarily composed of layers of aligned collagen that reorganize through out pregnancy resulting in softening, shortening, and dilation at term. Premature changes during the softening process may be associated with preterm birth. The purpose of this study is to compare shear wave speed (SWS) estimates in the ex vivo non-pregnant and in vivo third trimester pregnant cervix and to discuss confounding factors that may influence comparisons of SWS estimates. Ex vivo hysterectomy samples (n = 22) were collected and a subset were ripened (softened) (n = 13). Multiple SWS measurements were made longitudinally along the cervical canal at 4-5 locations on both anterior and posterior halves of the bivalved cervix. For the in vivo study, patients (n = 10) undergoing cervical ripening for induction of labor were recruited. SWS measurements were made on the same patient with the probe placed on the anterior half of the cervix at mid-length between the internal and external os. Ten replicate SWS measurements were made before and 4 hours after a cervical ripening agent (misoprostol) was administered. Statistical analysis was performed to determine significance of differences in SWS as a result of ripening. The SWS estimates for the mid-length anterior position for the ex vivo study were 3.42±0.92 m/s and 2.06±0.39 m/s for unripened and ripened, respectively. Similarly, the SWS estimates for the in vivo third trimester pregnant cervix were 2.40±0.75 m/s and 1.54±0.31 m/s pre- and post-ripening. Factors such as bivalving the ex vivo specimens, differences in tissue temperature, and tissue perfusion likely affect SWS estimates, but similar similar trends were found.
