Strain Elastography as a New Method for Assessing Pelvic Floor Biomechanics

Abstract

Strain elastography (SE) is a new technique of parametric imaging that allows quantification of the elasticity of tissue. The aim of our study was to determine if the elasticity of para-urethral tissue correlates with urethral mobility and urinary incontinence (UI). Ninety-nine unselected women were investigated with SE. They were given a standardized interview about UI, and SE raw data for the para-urethral tissue were acquired in a sagittal standard urethra-symphysis view while being stimulated by a coughing fit. We placed one region of interest (ROI A) in the tissue between the urethra and vagina at midlevel of the urethra bordering the urethral wall. The second ROI (ROI B) was set at the level of the os urethra internum in the tissue of the bladder neck in one line to ROI A. We measured elasticity in both ROIs with TDI-Q (Tissue Doppler Imaging-Quantification Software) and calculated the ratio between ROI A and ROI B (A/B). Mobility of the urethra was quantified by measuring the angle between a line parallel to the urethra and a line parallel to the bladder neck during stress and rest. SE analysis was feasible in all cases. A/B was found to be correlated with the incidence of urethral mobility (p < 0.001). The incidence of UI was associated with an increase in urethral mobility (p = 0.04). No correlation between UI and A/B could be shown (p = 0.24). We observed a correlation between urethral mobility and elasticity of the para-urethral tissue. In case of increasing urethral mobility, the para-urethral tissue close to the bladder neck seems to be more elastic, and the patients reported about more symptoms of UI. No noticeable correlation between UI and urethral elasticity was shown. SE may be a useful technique for direct quantification of tissue elasticity and assessment of pelvic floor biomechanics.

Keywords: Doppler ultrasound; Urinary incontinence; elastography; para-urethral tissue; strain.