Evaluation of the cervix tissue homogeneity by ultrasound elastography in infertile women for the prediction of embryo transfer ease: a diagnostic accuracy study

Abstract

Background: Ultrasound elastography is a non-invasive medical imaging technique able to quantitatively characterize the stiffness of a given tissue. It has been shown to predict the risk for cervical insufficiency and preterm delivery, and to allow differentiation of malignancy from normal tissue. The present study sought to evaluate whether cervical tissue dishomogeneity, as assessed by cervical ultrasound elastography, may predict the embryo transfer (ET) ease in infertile women undergoing IVF/ICSI.

Methods: We evaluated 154 infertile patients with no history of previous ET or intrauterine insemination. Cervical stiffness was evaluated in six regions of interest (ROI), compared two by two to obtain strain ratio (SR) values. Since a SR value of 1 was suggestive of tissue homogeneity, we computed 1-SR/SR-1 values to obtain a measure of the degree of cervical tissue dishomogeneity that we named "dishomogeneity index" (DI). Ultrasound-guided ET was performed by an expert operator blinded to the results of cervical elastography. The prediction ability of elastography on ET ease was evaluated by binary logistic regression, and the predictive accuracy of the independent variables was quantified with area under the curve (AUC) estimates derived from receiver operating characteristic (ROC) curve.

Results: ET resulted to be easy in 99 out of 154 patients (64,2%), difficult in 54 patients (35%), and impossible in one. DI values in cervical medial lips region correctly classified 86.9% of patients, according to binary logistic regression, with a sensitivity of 81.4% and a specificity of 89,9%, positive likelihood ratio (LR) 8.07 and negative LR of 0.21. A DI cut-off value of 0.29 predicted a difficulty of ET with a sensitivity of 88,9% and a specificity of 85%.

Conclusions: Cervical ultrasound elastography, by allowing the identification of cervical tissue dishomogeneity, may be of help in predicting the ET ease in infertile women candidates to IVF/ICSI.

Keywords: Assisted reproduction; Cervical canal; Elastography; Embryo transfer; Female infertility.

Fig. 1

Cervical elastography. a Identification of six regions of interest (ROI) in the cervix. The cervical canal is highlighted in yellow, and the internal and external uterine orifice are indicated with the symbol * and # respectively; b Cervical elastography in a normal case. The difference in tissue stiffness is expressed with a color scale. The green spring on the lower right end side is a real-time feedback of the correct performance of the strain image acquisition

Fig. 2

Comparison of elastographic evaluation in a case with easy, difficult and impossible embryo transfer. a Cervical channel appears red, while the surrounding tissue comprehensive of the six regions of interest (ROI) appears uniformly green with rare blue spots. Embryo Transfer (ET) resulted to be easy; b Cervical canal is not uniformly defined, and surrounding tissue shows a dishomogeneous color pattern. ET resulted to be difficult; c Cervical canal appears to be partially obstructed by a hyperechoic tissue in grey scale image, while elastographic image demonstrates the presence of diffuse tissue dishomogeneity. ET was not feasible, and we had to proceed with a transmiometrial ET