In vivo human assessment of bladder elasticity and compliance using Ultrasound Bladder Vibrometry (UBV) and comparison with urodynamic studies

Abstract

The bladder stiffens with age and various pathological processes. We have previously proposed the use of Ultrasound Bladder Vibrometry (UBV) to measure mechanical properties of the bladder wall. In UBV, ultrasound radiation force is focused at the bladder wall to excite impulsive anti-symmetric Lamb waves, and pulse-echo ultrasound is used to track tissue motion. Fourier-space analysis of tissue motion is used to calculate Lamb wave velocity dispersion, i.e. the change of Lamb wave velocity as a function of frequency. The Lamb wave velocity dispersion equation is fit to the dispersion data to estimate bladder viscoelastic parameters. Ex vivo formalin studies aimed at demonstrating the ability of UBV to detect bladder stiffening are demonstrated. UBV measurements of compliant and incompliant neurogenic patient bladders were compared with concomitant Urodynamic Cystometry Studies (UDS), which are the clinical gold standard for evaluation of bladder compliance. Results of UBV and UDS measurements in neurogenic patients were in good agreement. Healthy bladders were more compliant than the neurogenic bladders as their bladder elasticity does not increase significantly over the full range of bladder capacity. The results presented in this study demonstrate the potential of UBV serving as a surrogate to UDS studies.