Recommendations for strain elastography of the uterine cervix

Conventional vaginal strain ultrasound elastography, not based on shear-wave elastography imaging, can assess the biomechanical properties of the uterine cervix. This assessment may inform the risks of preterm birth and failed induction of labor. However, there is considerable variation in the approaches to strain elastography, including the placement of the region of interest (ROI). Therefore, our aim was to provide recommendations for cervical elastography.

We conducted a literature review on (1) elastography principles, and (2) the cervical anatomy. Subsequently, we performed elastography scanning using a Voluson^™ E10 Expert scanner with the BT18 software of (3) polyacrylamide hydrogel simulators, and (4) pregnant women.

Increasing the distance between the ROI and probe led to a decrease in the obtained strain value; a 53% decrease was observed at 17.5 mm. Similarly, an increased angle between the ROI and probe-centerline resulted in a 59% decrease for 40° angle. Interposition of soft tissue (e.g., cervical canal) between the ROI and the probe induced an artifact with values from the posterior lip being 54% lower than those from the anterior lip, even after adjusting for probe-ROI distance. Equipment and the recording conductance significantly influenced the results.

Our findings inform recommendations for future studies on strain cervical elastography.