title: Signal processing in urodynamics: towards high definition urethral pressure profilometry.
abstract: BACKGROUND
  Urethral 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.
  
  
  METHODS
  We 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.
  
  
  RESULTS
  Experimental 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.
  
  
  CONCLUSIONS
  With 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.
authors.affiliation: Institute for System Dynamics, University of Stuttgart, Waldburgstr. 17/19, 70563, Stuttgart, Germany. mario.kluender@isys.uni-stuttgart.de.
authors.forename: Mario
authors.initials: M
authors.lastname: Klünder
authors.affiliation: Institute for System Dynamics, University of Stuttgart, Waldburgstr. 17/19, 70563, Stuttgart, Germany.
authors.forename: Oliver
authors.initials: O
authors.lastname: Sawodny
authors.affiliation: Department of Urology, University of Tübingen, Hoppe-Seyler-Straße 3, 72076, Tübingen, Germany.
authors.forename: Bastian
authors.initials: B
authors.lastname: Amend
authors.affiliation: Institute for System Dynamics, University of Stuttgart, Waldburgstr. 17/19, 70563, Stuttgart, Germany.
authors.forename: Michael
authors.initials: M
authors.lastname: Ederer
authors.affiliation: Department of Urology, University of Tübingen, Hoppe-Seyler-Straße 3, 72076, Tübingen, Germany.
authors.forename: Alexandra
authors.initials: A
authors.lastname: Kelp
authors.affiliation: Department of Urology, Paracelsus Medical University of Salzburg, Müllner Hauptstr. 48, 5020, Salzburg, Austria.
authors.forename: Karl-Dietrich
authors.initials: KD
authors.lastname: Sievert
authors.affiliation: Department of Urology, University of Tübingen, Hoppe-Seyler-Straße 3, 72076, Tübingen, Germany.
authors.forename: Arnulf
authors.initials: A
authors.lastname: Stenzl
authors.affiliation: Institute for System Dynamics, University of Stuttgart, Waldburgstr. 17/19, 70563, Stuttgart, Germany.
authors.forename: Ronny
authors.initials: R
authors.lastname: Feuer
mesh_terms: D000465:Algorithms; D000818:Animals; D057785:Catheters; D003950:Diagnostic Techniques, Urological / Q000295:instrumentation*; D005260:Female; D011312:Pressure; D012815:Signal Processing, Computer-Assisted; D013552:Swine; D013556:Swine, Miniature; D014521:Urethra / Q000503:physiopathology*; D014550:Urinary Incontinence, Stress / Q000175:diagnosis / Q000503:physiopathology; D014563:Urodynamics
keywords: Signal processing; Urethral pressure; Urodynamics