Repeatability and reproducibility of quantitative cervical strain elastography (E-Cervix) in pregnancy

Abstract

Strain elastography of the uterine cervix may be useful in the diagnosis and prediction of obstetric complications. The inability to obtain quantitative results, with only the possibility of visual semiquantitative evaluation of the obtained elastograms, has been the limitation of the method thus far. E-Cervix is a software program that uses intrinsic compression to excite tissue and allows the evaluation of quantitative parameters on the basis of pixel distribution in an elastogram. The aim of this study was to assess the repeatability and reproducibility of quantitative cervical strain elastography (E-Cervix) of the uterine cervix and to assess the correlation of the obtained parameters with selected clinical features of patients in the third trimester of pregnancy. In total, 222 patients participated in the study. We assessed 5 ultrasound parameters: elasticity index (ECI), hardness ratio (HR), internal os strain (IOS), external os strain (EOS) and IOS/EOS ratio. Each study was performed according to a predetermined standardized protocol. For all assessed elastographic parameters, we obtained good intra- and interobserver reproducibility. The interclass correlation coefficient (ICC) ranged from 0.77 to 0.838 for intraobserver variability and from 0.771 to 0.826 for interobserver variability. We demonstrated a significant correlation of some obtained elastographic parameters with the basic clinical features of patients, such as age, the number of previous caesarean sections, pregnancy weight and BMI. In each case, the correlation was very low. Quantitative elastographic assessment with the use of E-Cervix is characterized by good repeatability. Some clinical features may affect the value of the parameters obtained. The clinical relevance of this interference requires further investigation.

Figure 1

Sample image of the cervix obtained in the study. (a) The dashed white line represents the endocervical canal; (b) the internal and external cervical os are represented by the white circular sectors; and (c) the green 6-point sector represents the ROI. In the lower right corner, you can see the values ​​of the E-Cervix parameters.

Figure 2

Bland–Altman plots showing the degree of agreement between two examinations with respect to measuring individual E-Cervix parameters. Intrarater agreement and interrater agreement of cervical length (1,2) ECI (3,4), EOS (5,6), IOS (7,8) and HR (9,10) measurements.

Figure 2

Bland–Altman plots showing the degree of agreement between two examinations with respect to measuring individual E-Cervix parameters. Intrarater agreement and interrater agreement of cervical length (1,2) ECI (3,4), EOS (5,6), IOS (7,8) and HR (9,10) measurements.

Figure 2

Bland–Altman plots showing the degree of agreement between two examinations with respect to measuring individual E-Cervix parameters. Intrarater agreement and interrater agreement of cervical length (1,2) ECI (3,4), EOS (5,6), IOS (7,8) and HR (9,10) measurements.

Figure 2

Bland–Altman plots showing the degree of agreement between two examinations with respect to measuring individual E-Cervix parameters. Intrarater agreement and interrater agreement of cervical length (1,2) ECI (3,4), EOS (5,6), IOS (7,8) and HR (9,10) measurements.

Figure 2

Bland–Altman plots showing the degree of agreement between two examinations with respect to measuring individual E-Cervix parameters. Intrarater agreement and interrater agreement of cervical length (1,2) ECI (3,4), EOS (5,6), IOS (7,8) and HR (9,10) measurements.