Quantitative analysis of uterine motion outside pregnancy by dedicated ultrasound speckle tracking

A dedicated method for quantification of uterine motion and strain outside pregnancy by B-mode transvaginal ultrasound (TVUS) is here presented. Motion analysis was implemented by speckle tracking based on block matching using sum of absolute differences as the matching criterion. Prior to the analysis, the speckle-size was regularized by Wiener deconvolution and Singular Value Decomposition (SVD) filtering was used to enhance the uterine motion. The SVD filter and speckle tracking parameters were first optimized ex vivo by a dedicated setup and then translated in vivo. In vivo, the speckle tracking was accelerated by a diamond search (DS) strategy. Robustness to speckle decorrelation was improved by taking the median shift of surrounding blocks. The method feasibility was tested on 9 healthy women for its ability to distinguish between different uterine phases in the menstrual cycle. For each image sequence, two pairs of sites were selected around the internal lining of the uterus and tracked over time to derive distance and strain signals along the longitudinal direction of the uterus. Among the extracted amplitude and frequency features, the latter ones permitted successful separation between different phases (p < 0.05 by Dunn-Sidak post hoc test). These promising results suggest our proposed method to produce effective enhancement and tracking of uterine motion and motivate towards an extensive validation in the context of fertilization procedures.