Quantitative analysis of uterine peristalsis in women with adenomyosis using optical flow for motion quantification

RESEARCH QUESTION: Do women with adenomyosis have altered uterine peristalsis, and can an objective and reproducible tool be developed to quantify uterine peristalsis on transvaginal sonography (TVS)? DESIGN: Prospective observational cohort study in women with moderate to severe adenomyosis (n = 26) or a normal uterus (n = 40) undergoing TVS during assisted conception. TVS recordings (n = 143) were conducted at baseline, day 6-10 of ovarian stimulation and day of embryo transfer by operator A, and then repeated by operator A, B or C. Image data were stored offline for optical flow analysis. Pixel-level displacements for points at the endometrial--myometrial junction were used to compute peristalsis frequency and amplitude by fitting to the two-dimensional wave equation. Fit error was taken as a measure of wave coordination. Inter-class correlation coefficient (ICC) was calculated to assess inter- and intra-observer agreement. RESULTS: Women with adenomyosis had a significantly higher fit error at all time points during the IVF cycle (baseline: + 0.725, P < 0.001; ovarian stimulation: + 0.612, P = 0.004; embryo transfer: + 0.627, P < 0.001), indicating lower uterine peristalsis coordination compared with women with a normal uterus. Inter- and intra-observer agreement for each wave feature (frequency, amplitude and coordination of uterine peristalsis and myometrial contractility) was found to be moderate to good (intra-observer ICC: 0.62-0.75, inter-observer ICC: 0.58-0.79). CONCLUSION: An objective and reproducible measuring tool is proposed to quantify uterine peristalsis using TVS, with potential for wide application across assisted conception and gynaecology settings.