| Soon after conception, the microstructure of the cervix begins to 'remodel', and just before delivery this remodeling accelerates as the cervix also shortens and dilates. Premature changes during this process may be associated with preterm birth (birth at less than 37 weeks gestational age), which is the leading cause of neonatal death. Of particular interest is cervical softening (and the mechanisms causing it), which initiates early (weeks after conception). Currently, the clinical method for assessing the cervix involves manual palpation and a subjective classification of cervical softness into one of three categories (soft, medium, and firm). Our goal was to develop objective, quantitative methods to evaluate cervical softness. Shear Wave Elasticity Imaging (SWEI) is a non-invasive method to quantify tissue softness. The basic principle is that measuring shear wave speeds in tissue provides objective information about stiffness/softness because shear waves travel faster in stiffer tissue. The cervix presents a specific challenge for SWEI methods because it is comprised of heterogeneous layers of pseudo-aligned collagen that remodel throughout pregnancy. Its complicated structure may increase variance and/or violate assumptions in estimation of quantitative parameters. Therefore, this investigation was designed to optimize and validate SWEI methods specific to cervical assessment, establish spatial and biological variability of shear wave speed (SWS) estimates in the ex vivo non-pregnant cervix, assess the sensitivity of SWS estimates at different stages during pregnancy in vivo, and finally to investigate the relationship between shear wave propagation and collagen structure in the cervix. The contributions of this work will be beneficial to quantitatively assess cervical softening in more large-scale clinical studies during pregnancy. |
