Estimation of shear wave speed in the human uterine cervix

Abstract

Objectives Our goals were to explore the spatial variability within the cervix and the sensitivity of shear wave speeds (SWS) to assess softness/stiffness differences in ripened (softened) versus unripened tissue. Methods We obtained SWS estimates from hysterectomy specimens (n=22), a subset of which were ripened (n = 13). Multiple measurements were made longitudinally along the cervical canal on both the anterior and posterior sides of the cervix. Statistical tests of differences in the proximal vs. distal, anterior vs. posterior, and ripened vs. unripened cervix were performed with individual two-sample t-tests and a linear mixed model. Results We discovered that SWS estimates monotonically increase from distal to proximal longitudinally along the cervix, that they also vary in the anterior compared to the posterior cervix, and that they are significantly different in ripened vs. unripened cervical tissue. Specifically, the mid position SWS estimates for the unripened group were 3.45±0.95 m/s (anterior) and 3.56±0.92 m/s (posterior), and 2.11±0.45 m/s (anterior) and 2.68±0.57 m/s (posterior) for the ripened (p<0.001). Conclusions We propose that shear wave speed estimation may be a valuable research and, ultimately, diagnostic tool for objective quantification of cervical stiffness/softness.

Quantification of elasticity changes in the myometrium during labor using Supersonic Shear Imaging: A feasibility study

“…This technique, in which strain maps of tissues are calculated after applying static stress directly onto the surface of the body with the ultrasonic probe, provides information on the relative stiffness of the tissues investigated, but is highly operator dependant and non-quantitative. Such drawbacks can be overcome by using dynamic elastography techniques [17,9,16,7,8], which allow for the generation of reproducible and quantitative elasticity maps. In this paper, Supersonic Shear Wave Imaging (SSI) [8] is used to map the stiffness of the uterus during the myometrium contraction.…”

Comparison of shear wave speed estimates in Ex vivo non-pregnant vs. In vivo pregnant cervix

“…Nine of these subjects were not experiencing bleeding at the time of surgery (the "unripened" group), 6 were experience bleeding or dysmenorrhea (painful menstruation; the "uterine bleeding" group), and 7 subjects were given misoprostol, a prostaglandin agent used to soften the cervix prior to many gynecologic procedures, 10-12 hours prior to surgery (the "misoprostolripened" group). The "uterine bleeding" and "misoprostolripened" groups were combined based on statistical equivalence into a single "ripened" group (n = 13) [12], [13]. All subjects provided informed consent, and all work was HIPAA compliant and approved by the IRBs at Intermountain Healthcare and the University of Wisconsin.…”

Using speckle statistics to improve attenuation estimates for cervical assessment

“…Studies have shown that as the delivery time approaches the collagen rich cervix is filled with water and enzymes which results in a lower attenuation value and a softening of the cervix as it prepares for delivery [23][24][25]. Our earlier work showed that attenuation of the cervix decreased as the cervix prepared for delivery [8][9][10][11][12] while the softening of the cervix can also be quantified using shear wave elastography [13][14][15].…”

“…Our earlier work showed that attenuation of the cervix decreased as the cervix prepared for delivery [8][9][10][11][12]. The softening of the cervix can also be quantified using shear wave elastography [13][14][15]. In this method a stress is created and then the strain in the tissue is observed from that stress.…”