Pitfalls in the use of shear wave elastography on the cervix

Abstract

Introduction Ultrasound shear wave elastography has the potential to assess the strength of the maternal cervix for signs of insufficiency.1, 2 The reliability of shear wave elastography in biological tissues can be affected by numerous ultrasound artifacts and prestress of tissues in the region of interest can also affect the shear wave speed. This study investigates the use of the transvaginal ultrasound approach to obtain shear wave speeds in the uterine cervix with the aim of identifying factors that affect shear wave speed and transmission. Objectives The primary aim of this study is to identify biological and technical confounders for the use of two dimensional shear wave elasography applied to the uterine cervix. The goal was to identify confounders, and develop shear wave technique in the low risk non-gravid population. Methods Sixty nine non-gravid participants with varying medical history and ethnicity consented to be part of this research. Inter-operator testing was performed on fifteen participants.Imaging methodology As an adjunct to the normal imaging examination extra imaging of cervical speed measurements using two dimensional shear wave elastography was performed.The transvaginal approach utilises an endocavity transducer with an empty maternal bladder. Shear wave elastography speed measurements are acquired at the external and internal os anterior and posterior portions. Results Reliable measurements were obtained at the external os and internal os, anteriorly and posteriorly, in 63, 55, 55 and 26 patients respectively. The mean speed obtained at the external os, anteriorly and posteriorly, was 2.52 ± 0.49 m/s and 2.87 ± 0.63 m/s respectively, and at the internal os anteriorly and posteriorly, 3.29 ± 0.79 m/s and 4.10 ± 1.11 m/s respectively. The difference in speed between all regions was statistically significant] (p Interoperator testing The intraclass correlation coefficient obtained at the regions of the cervix was as follows - external os anterior 0.83 (CI 0.45 – 0.95), external os posterior 0.69 (CI 0.07-0.90), internal os anterior 0.92 (CI 0.76 – 0.97), internal os posterior 0.90 (CI 0.37-0.98) Conclusion Biological factors and ultrasound induced artifacts appear to affect the transmission of the elastographic main pulse, with cervical position appearing to affect shear wave production. Reliable shear wave propagation can be achieved in the anterior cervix in most patients.