Quantitative elastography of cervical stiffness during the three trimesters of pregnancy with a semiautomatic measurement program: A longitudinal prospective pilot study

Reproducibility of quantitative cervical strain elastography in nonpregnant patients and the effect of vaginal misoprostol on measured parameters

Quantitative strain elastography (SE), referred to as E-Cervix (Samsung Medison), is a novel method for assessing parameters that indirectly describe the elasticity of the cervix. This evaluation yields quantitative parameters based on the analysis of the elastographic map image, which represents a new approach in the context of SE. In our study, we aimed to examine the reproducibility of this method in evaluating the cervix of non-pregnant women, the impact of basic demographic parameters of the patient on the results, and the responsiveness of the method, i.e., the assessment of changes occurring in the results after the vaginal application of a 400 µg dose of misoprostol. We included 80 patients scheduled for hysteroscopy who underwent elastographic examination using the E-Cervix module. The examination was performed twice upon admission to the department by the same ultrasonographer and then again 10-12 h after vaginal application of misoprostol, consecutively by two ultrasonographers. Our study demonstrated high reproducibility of all obtained parameters, with ICC (Intraclass Correlation Coefficient) for intraobserver variability being good to excellent, ranging from 0.85 for ECI (Elasticity index) to 0.94 for IOS (Internal Os strain)/EOS (External Os strain) ratio. For interobserver variability, ICC values ranged from 0.76 for ECI to 0.97 for IOS/EOS ratio. We observed no significant correlation between parameters such as height, weight, BMI (body mass index), and the number of births in the patient's history and the values of elastographic parameters. We found weak to moderate positive correlations between the day of the cycle in which the patient was and ECI (rho = 0.28), EOS (rho = 0.41), IOS/EOS ratio (rho = 0.33). The study observed a significant increase in the median value of the HR (Hardness ratio) parameter after the application of vaginal misoprostol (median difference = 5.32), an increase in EOS (difference of the medians = 0.04), and a significant decrease in IOS/EOS ratio (difference of medians = - 0.05). In our study, we demonstrated high reproducibility and repeatability of E-Cervix parameters in non-pregnant women and showed a negligible influence of most demographic factors on the study outcomes, as well as changes in parameter values under the influence of drugs affecting cervical elasticity. The method appears to be suitable for evaluating the cervix in non-pregnant women.

Cervical elastography at 18 to 23 weeks to predict spontaneous preterm birth in individuals with a history of preterm birth

BACKGROUND

Individuals with a history of spontaneous preterm birth are at increased risk for recurrence in a subsequent pregnancy. Current methods used to predict those at highest risk are not precise. Cervical elastography is an investigational ultrasonographic technique that measures cervical tissue stiffness and may aid in identifying individuals at highest risk.

OBJECTIVE

This study aimed to assess the association between previously described cervical elastography measures-obtained using a semiautomatic application (E-cervix)-and preterm birth <37 weeks' gestation in a high-risk cohort with a history of spontaneous preterm birth.

STUDY DESIGN

Individuals with a singleton pregnancy between 18+0 and 23+6 weeks of gestation with a history of spontaneous preterm birth <37 weeks were prospectively enrolled. Exclusion criteria included the presence of a current cerclage or any uterine anomaly. The primary exposures were the E-cervix quantitative parameters (internal os stiffness, external os stiffness, internal-to-external os stiffness ratio, hardness ratio, and elasticity contrast index), which were measured at the time of enrollment. Transvaginal cervical length was also measured as an exposure to compare the current standard of care and accepted cutpoint of 25 mm alongside the E-cervix parameters. The primary outcome was preterm birth <37 weeks. The intra- and interrater reliability intraclass correlation coefficient for each parameter was calculated using a mixed-effects model. The area under the curve was derived from receiver operating characteristic curves to evaluate the association of each parameter with the primary outcome, and the optimal cutpoints for each continuous parameter were identified. Multivariable logistic regression was performed for the parameters that were either significant on univariate analysis or had an area under the curve of ≥0.6, using the calculated cutpoint to create a binary exposure and adjusting for gestational age at the earliest prior preterm birth, number of prior preterm births, and progesterone use. A sensitivity analysis was performed excluding medically indicated preterm birth.

RESULTS

Of the enrolled 245 individuals with a history of spontaneous preterm birth, 69 (28%) had preterm birth <37 weeks. Intrarater and interrater reliability were good for all parameters (intrarater: 0.60-0.74; interrater: 0.62-0.71). In univariate analysis, only the internal-to-external os stiffness ratio was significantly associated with increased risk of preterm birth compared with no preterm birth (0.97±0.23 vs 0.90±0.20; P=.01). Cervical length, internal os stiffness, external os stiffness, hardness ratio, and elasticity contrast index did not show significant associations. The area under the curve for external os stiffness was 0.6, indicating a good association, whereas the values for the remaining parameters were satisfactory (0.51-0.59). In multivariable logistic regression analysis, an internal-to-external os stiffness ratio ≥1.0 was associated with 2-fold higher odds of preterm birth <37 weeks (adjusted odds ratio, 2.48; confidence interval, 1.34-4.58), and an external os stiffness ≥30 (indicating lower tissue stiffness) was associated with 46% reduced odds of preterm birth <37 weeks (adjusted odds ratio, 0.54; confidence interval, 0.30-0.97). Cervical length <25 mm was not associated with preterm birth.

CONCLUSION

Elastography with E-cervix technology can be reliably assessed in a cohort of women with prior preterm birth. The parameter most useful for predicting preterm birth was an internal-to-external os stiffness ratio ≥1.0, whereas cervical length <25 mm was not predictive in our cohort.

Uterus and cervix anatomical changes and cervix stiffness evolution throughout pregnancy

The coordinated biomechanical performance, such as uterine stretch and cervical barrier function, within maternal reproductive tissues facilitates healthy human pregnancy and birth. Quantifying normal biomechanical function and detecting potentially detrimental biomechanical dysfunction (e.g., cervical insufficiency, uterine overdistention, premature rupture of membranes) is difficult, largely due to minimal data on the shape and size of maternal anatomy and material properties of tissue across gestation. This study quantitates key structural features of human pregnancy to fill this knowledge gap and facilitate three-dimensional modeling for biomechanical pregnancy simulations to deeply explore pregnancy and childbirth. These measurements include the longitudinal assessment of uterine and cervical dimensions, fetal weight, and cervical stiffness in 47 low-risk pregnancies at four time points during gestation (late first, middle second, late second, and middle third trimesters). The uterine and cervical size were measured via 2-dimensional ultrasound, and cervical stiffness was measured via cervical aspiration. Trends in uterine and cervical measurements were assessed as time-course slopes across pregnancy and between gestational time points, accounting for specific participants. Patient-specific computational solid models of the uterus and cervix, generated from the ultrasonic measurements, were used to estimate deformed uterocervical volume. Results show that for this low-risk cohort, the uterus grows fastest in the inferior-superior direction from the late first to middle second trimester and fastest in the anterior-posterior and left-right direction between the middle and late second trimester. Contemporaneously, the cervix softens and shortens. It softens fastest from the late first to the middle second trimester and shortens fastest between the late second and middle third trimester. Alongside the fetal weight estimated from ultrasonic measurements, this work presents holistic maternal and fetal patient-specific biomechanical measurements across gestation.

Evaluation of Non-Compressive Transvaginal Cervical Elastography as a Quantitative Imaging Biomarker in Pregnancy: A Repeatability and Reliability Analysis

OBJECTIVES

Non-compressive strain elastography has been proposed as a novel quantitative imaging biomarker for assessing the structure and function of the cervix. The current study aims to assess the repeatability, and intra- and inter-observer reliability of transvaginal non-compressive cervical strain elastography in a clinical setting.

METHODS

We conducted a dual-phase single-center prospective feasibility study of singleton gestations >16-weeks gestation that required a clinically-indicated transvaginal ultrasound. Each study participant, n = 43 in phase 1 and n = 13 in phase 2, had elastography performed by two trained observers that each performed multiple image acquisitions. We performed a multivariable regression to adjust for changes in clinical characteristics between study phases and calculated the repeatability coefficients, limits of agreement, and intraclass correlations for each quantitative elastography parameter. We compared quantitative elastography parameters to cervical length measurements, acquired from the same images.

RESULTS

The repeatability coefficients and percent limits of agreement were wide for all of the quantitative elastography parameters, demonstrating poor repeatability. Intraclass correlation coefficients were poor-moderate for both intra-observer (0.31-0.77) and inter-observer reliability (0.35-0.77) in both study phases, while cervical length showed excellent reliability with intraclass correlations consistently >0.90.

CONCLUSIONS

Non-compressive transvaginal strain cervical elastography did not demonstrate adequate repeatability or reliability. Our results highlight the importance of rigorously assessing novel quantitative imaging biomarkers before clinical application.

Prediction model for successful induction of labor by cervical strain elastography diagnosed at late-term pregnancy in nulliparous women: a prospective cohort study

BACKGROUND

The use of cervical strain elastography for nulliparous women during late-term pregnancy remains unclear. This study assesses the predictive value of late-term cervical strain elastography for successful induction of labor (IOL) in nulliparous women.

METHODS

This single-centered, prospective study included 86 patients undergoing IOL between January 2020 and March 2022. Univariate and multivariate analyses were conducted to identify predictive factors for successful IOL. The predictive values were assessed using the area under receiver operating characteristic (ROC) curves.

RESULTS

IOL was successful in 58 patients. The hardness ratio and cervical length were significantly associated with successful late-term IOL in nulliparous women. The predictive value of the combination of hardness ratio and cervical length was higher than that of cervical length alone.

CONCLUSIONS

The hardness ratio and cervical length assessed by cervical strain elastography during late-term pregnancy are predictors of the success of IOL in nulliparous women. The predictive value of the combination of hardness ratio and cervical length was higher than that of cervical length alone.

Advances in the clinical application of ultrasound elastography in uterine imaging

Changes in tissue stiffness by physiological or pathological factors in tissue structure are identified earlier than their clinical features. Pathological processes such as uterine fibrosis, adenomyosis, endometrial lesions, infertility, and premature birth can manifest as tissue elasticity changes. In clinical settings, elastography techniques based on ultrasonography, optical coherence tomography, and magnetic resonance imaging are widely used for noninvasive measurement of mechanical properties in patients, providing valuable tool and information for diagnosis and treatment. Ultrasound elastography (USE) plays a critical role in obstetrics and gynecology clinical work because of its simplicity, non-invasiveness, and repeatability. This article reviews the recent progress of USE in uterine tumor diagnosis (especially early diagnosis and treatment effect evaluation), prediction of preterm birth, and intrauterine insemination. We believe that USE, especially shear wave elastography, may serve as a potential means to assess tissue stiffness, thereby improving the diagnosis and treatment of adenomyosis, fibroids, endometrial lesions, cervical cancer, and precise management of preterm birth and intrauterine insemination monitoring.

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

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.

Predictive value of cervical length by ultrasound and cervical strain elastography in labor induction at term

OBJECTIVE

This study aimed to examine whether addition of cervical elastographic parameters measured by ElastoScan for the cervix (E-cervix) improves the predictive value of cervical length (CL) in induction of labor at term by dinoprostone.

METHODS

We conducted a prospective, observational study between January 2020 and June 2020 in term primiparous women (n = 73) who were scheduled for labor induction by a 10-mg dinoprostone vaginal insert. The time intervals from the start of labor induction to regular uterine contractions and to vaginal delivery were calculated as the primary outcomes. We divided subjects into two groups using a threshold of 24 hours. Ultrasound measurements were compared between the two groups and the area under the curve (AUC) of the prediction model was calculated.

RESULTS

Women who delivered vaginally within 24 hours had a shorter CL and softer cervix than those who delivered after 24 hours. The combination of CL and elastographic parameters increased the AUC to 0.672 compared with CL alone (AUC = 0.637).

CONCLUSIONS

Measurement by E-cervix is relatively reproducible. Addition of cervical strain elastography slightly improves the predictive performance of CL in vaginal delivery within 24 hours. This technique is a promising ancillary tool for use with ultrasound.

Uterine Cervical Change at Term Examined Using Ultrasound Elastography: A Longitudinal Study

The aim of the study was to investigate if there are changes in elastographic parameters in the cervix at term around the time of delivery and if there are differences in the parameters between women with spontaneous labor and those without labor (labor induction). Nulliparous women at 36 weeks of gestation eligible for vaginal delivery were enrolled. Cervical elastography was performed and cervical length were measured using the E-Cervix^TM system (WS80A Ultrasound System, Samsung Medison, Seoul, Korea) at each weekly antenatal visit until admission for spontaneous labor or labor induction. E-Cervix parameters of interest included elasticity contrast index (ECI), internal os strain mean level (IOS), external os strain mean level (EOS), IOS/EOS strain mean ratio, strain mean level, and hardness ratio. Regression analysis was performed using days from elastographic measurement at each visit to admission for delivery and the presence or absence of labor against cervical length, and each E-Cervix parameter fitted to a linear model for longitudinal data measured repeatedly. A total of 96 women were included in the analysis, (spontaneous labor, n = 39; labor induction, n = 57). Baseline characteristics were not different between the two groups except for cesarean delivery rate. Cervical length decreased with advancing gestation and was different between the two groups. Most elastographic parameters including ECI, IOS, EOS, strain mean, and hardness ratio were significantly different between the two groups. In addition, ECI, IOS, and strain mean values significantly increased with advancing gestation. Our longitudinal study using ultrasound elastography indicated that E-cervix parameters tended to change linearly at term near the time of admission for delivery and that there were differences in E-Cervix parameters according to the presence or absence of labor.