Measuring cervical strain with tissue Doppler imaging depending on the shape and placement of the region of interest and its correlation with cervical consistency index

Abstract

Objectives: We want to evaluate tissue Doppler imaging (TDI) for measuring cervical strain. We compare three different methods for measuring strain depending on the region of interest (ROI) placement and evaluate patient discomfort. We correlate the strain measured through TDI with cervical consistency index (CCI), cervical length and width of both cervical lips.

Study design: This is a prospective study in 30 singleton primigravida pregnancies without obstetrical risks between 40+0 and 41+3 weeks of gestation. The CCI was calculated according to Parra-Saavedra et al. We tested three methods of measuring cervical elasticity depending on shape and location of ROIs.

Results: The CCI ranged between 36.4% and 71.9% with an average of 50.78%. The CCI shows negative correlation with strain and no correlation with cervical length or with the width of either cervical lip. The strain measurements regardless of tested method were reproducible and independent on cervical length. The average strain was higher in outer cervical regions. The ROIs placed on the anterior lip had higher reproducibility than those placed on the posterior lip. The average score for patient discomfort during examination was 3.7/10.

Conclusion: The strain depends on the size and location of ROIs. The circular ROIs with diameter equal to the width of the cervical lip are recommended. There is a correlation between CCI and TDI. The cervix shows heterogeneous consistency with increased stiffness from the outer to the inner sections. The TDI seems to be an easy to learn, quickly to perform, acceptable and reproducible method for measuring cervical elasticity. There is room for optimization and refinement of measuring methods before being tested for clinical significance.

Keywords: Cervical elastography; Cervical strain; Elasticity; TDI; Ultrasound.