Ultrasound urodynamic studies (US-UDS): noninvasive estimation of detrusor pressure through ultrasound

<i>Objective.</i>Urodynamic studies (UDSs) are vital for evaluating bladder function but require invasive catheterization to measure detrusor pressure (<i>P</i>_det). Our purpose is to report on technical developments toward a noninvasive and accurate estimation of<i>P</i>_detthrough ultrasound (US), a technique we refer to as US-UDS.<i>Approach.</i>The proposed US-UDS technique produces an estimate of<i>P</i>_detby using US to induce and track elastic waves that propagate within and around the bladder wall. Key components of the US-UDS processing include: an US sequence with dense time sampling; an empirical correction accounting for deviation from a Lamb wave dispersion model; and constrained optimization for<i>P</i>_detestimation. US-UDS analysis for estimation of<i>P</i>_detwas applied to 533 distinct data points collected from 3 human subjects undergoing concurrent UDS. Concordance analysis was used to evaluate agreement between US-UDS and UDS measures of<i>P</i>_detwhile response operator characteristic analysis was used to evaluate US-UDS for detection of detrusor activity (parameterized as UDS<i>P</i>_det>15 cmH₂O).<i>Main results.</i>US-UDS was able estimate<i>P</i>_detwithin 10 cmH₂O and 5 cmH₂O of UDS measurements with coverage probabilities of 95.7% and 68.8% respectively. Furthermore, US-UDS was able to detect UDS<i>P</i>_detmeasurements greater than 15 cmH₂O with a sensitivities and specificities of 0.99 and 0.83 using a fixed threshold (>15 cmH₂O for US-UDS) and 1.0 and 0.93 for an optimized threshold (> 11.08 cmH₂O for US-UDS).<i>Significance.</i>Our results show that the technical developments of US-UDS put forth in this work are able produce accurate and useful estimates of<i>P</i>_detas compared to traditional UDS. Although additional research with a large number of subjects is needed to fully characterize the clinical utility of US-UDS, the developments and results from this work demonstrate that clinically useful non-invasive measurements of<i>P</i>_detare feasible from US measurements.