Abstract
BackgroundUrethral pressure profilometry (UPP) is used in the diagnosis of stress urinary incontinence (SUI) which is a significant medical, social, and economic problem. Low spatial pressure resolution, common occurrence of artifacts, and uncertainties in data location limit the diagnostic value of UPP. To overcome these limitations, high definition urethral pressure profilometry (HD-UPP) combining enhanced UPP hardware and signal processing algorithms has been developed. In this work, we present the different signal processing steps in HD-UPP and show experimental results from female minipigs.MethodsWe use a special microtip catheter with high angular pressure resolution and an integrated inclination sensor. Signals from the catheter are filtered and time-correlated artifacts removed. A signal reconstruction algorithm processes pressure data into a detailed pressure image on the urethra’s inside. Finally, the pressure distribution on the urethra’s outside is calculated through deconvolution. A mathematical model of the urethra is contained in a point-spread-function (PSF) which is identified depending on geometric and material properties of the urethra. We additionally investigate the PSF’s frequency response to determine the relevant frequency band for pressure information on the urinary sphincter.ResultsExperimental pressure data are spatially located and processed into high resolution pressure images. Artifacts are successfully removed from data without blurring other details. The pressure distribution on the urethra’s outside is reconstructed and compared to the one on the inside. Finally, the pressure images are mapped onto the urethral geometry calculated from inclination and position data to provide an integrated image of pressure distribution, anatomical shape, and location.ConclusionsWith its advanced sensing capabilities, the novel microtip catheter collects an unprecedented amount of urethral pressure data. Through sequential signal processing steps, physicians are provided with detailed information on the pressure distribution in and around the urethra. Therefore, HD-UPP overcomes many current limitations of conventional UPP and offers the opportunity to evaluate urethral structures, especially the sphincter, in context of the correct anatomical location. This could enable the development of focal therapy approaches in the treatment of SUI.Electronic supplementary materialThe online version of this article (doi:10.1186/s12938-016-0145-6) contains supplementary material, which is available to authorized users.
Highlights
Urethral pressure profilometry (UPP) is used in the diagnosis of stress urinary incontinence (SUI) which is a significant medical, social, and economic prob‐ lem
Through sequential signal processing steps, physicians are provided with detailed information on the pressure distribution in and around the urethra
In order to assess the plausibility of the high definition urethral pressure profilometry (HD-UPP) pressure traces in Figs. 8, 9, 10a they can be compared to their respective pressure traces obtained with the air-charged catheter in Additional file 2
Summary
Urethral pressure profilometry (UPP) is used in the diagnosis of stress urinary incontinence (SUI) which is a significant medical, social, and economic prob‐ lem. They are prone to artifacts due to kinks or air bubbles in the tube, and their reference level needs to be reset when the patient changes position [3] This led to microtip catheters becoming the benchmark technology in multichannel urodynamics due to the reproducibility and reliability of their data [4,5,6]. Air-charged balloon-type catheters have gained popularity as they are single use (avoiding re-sterilization or possible transmission of infections) and easy to use They are considered to deliver excellent reproducibility reliability for UPP measurement even better than microtip catheters, as they measure pressure circumferentially which is considered more accurate and less prone to artifacts than unidirectional measurements [3, 6]. Compressibility of air, may negatively affect pressure recording fidelity [8] and the size of the balloon decreases resolution along the urethra as it acts as a moving-average filter
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