title: Noninvasive Evaluation of Bladder Wall Mechanical Properties as a Function of Filling Volume: Potential Application in Bladder Compliance Assessment.
abstract: OBJECTIVE
  We propose a novel method to monitor bladder wall mechanical properties as a function of filling volume, with the potential application to bladder compliance assessment. The proposed ultrasound bladder vibrometry (UBV) method uses ultrasound to excite and track Lamb waves on the bladder wall from which its mechanical properties are derived by fitting measurements to an analytical model. Of particular interest is the shear modulus of bladder wall at different volumes, which we hypothesize, is similar to measuring the compliance characteristics of the bladder.
  
  
  METHODS
  Three experimental models were used: 1) an ex vivo porcine model where normal and aberrant (stiffened by formalin) bladders underwent evaluation by UBV; 2) an in vivo study to evaluate the performance of UBV on patients with clinically documented compliant and noncompliant bladders undergoing UDS; and 3) a noninvasive UBV protocol to assess bladder compliance using oral hydration and fractionated voiding on three healthy volunteers.
  
  
  RESULTS
  The ex vivo studies showed a high correlation between the UBV parameters and direct pressure measurement (R2 = 0.84-0.99). A similar correlation was observed for 2 patients with compliant and noncompliant bladders (R2 = 0.89-0.99) undergoing UDS detrusor pressure-volume measurements. The results of UBV on healthy volunteers, performed without catheterization, were comparable to a compliant bladder patient.
  
  
  CONCLUSIONS
  The utility of UBV as a method to monitor changes in bladder wall mechanical properties is validated by the high correlation with pressure measurements in ex vivo and in vivo patient studies. High correlation UBV and UDS in vivo studies demonstrated the potential of UBV as a bladder compliance assessment tool. Results of studies on healthy volunteers with normal bladders demonstrated that UBV could be performed noninvasively. Further studies on a larger cohort are needed to fully validate the use of UBV as a clinical tool for bladder compliance assessment.
authors.affiliation: Department of Physiology and Biomedical Engineering, Mayo Clinic College of Medicine, Rochester, Minnesota, United States of America.
authors.forename: Ivan
authors.initials: I
authors.lastname: Nenadic
authors.affiliation: Department of Urology, Mayo Clinic College of Medicine, Rochester, Minnesota, United States of America.
authors.forename: Lance
authors.initials: L
authors.lastname: Mynderse
authors.affiliation: Department of Urology, Mayo Clinic College of Medicine, Rochester, Minnesota, United States of America.
authors.forename: Douglas
authors.initials: D
authors.lastname: Husmann
authors.affiliation: Department of Physiology and Biomedical Engineering, Mayo Clinic College of Medicine, Rochester, Minnesota, United States of America.
authors.forename: Mohammad
authors.initials: M
authors.lastname: Mehrmohammadi
authors.affiliation: Department of Physiology and Biomedical Engineering, Mayo Clinic College of Medicine, Rochester, Minnesota, United States of America.
authors.forename: Mahdi
authors.initials: M
authors.lastname: Bayat
authors.affiliation: Department of Physiology and Biomedical Engineering, Mayo Clinic College of Medicine, Rochester, Minnesota, United States of America.
authors.forename: Aparna
authors.initials: A
authors.lastname: Singh
authors.affiliation: Department of Radiology, Mayo Clinic College of Medicine, Rochester, Minnesota, United States of America.
authors.forename: Max
authors.initials: M
authors.lastname: Denis
authors.affiliation: Department of Physiology and Biomedical Engineering, Mayo Clinic College of Medicine, Rochester, Minnesota, United States of America.|Department of Radiology, Mayo Clinic College of Medicine, Rochester, Minnesota, United States of America.
authors.forename: Matthew
authors.initials: M
authors.lastname: Urban
authors.affiliation: Department of Physiology and Biomedical Engineering, Mayo Clinic College of Medicine, Rochester, Minnesota, United States of America.|Department of Radiology, Mayo Clinic College of Medicine, Rochester, Minnesota, United States of America.
authors.forename: Azra
authors.initials: A
authors.lastname: Alizad
authors.affiliation: Department of Physiology and Biomedical Engineering, Mayo Clinic College of Medicine, Rochester, Minnesota, United States of America.
authors.forename: Mostafa
authors.initials: M
authors.lastname: Fatemi
mesh_terms: D000328:Adult; D000818:Animals; D003187:Compliance; D006801:Humans; D055595:Mechanical Phenomena; D011312:Pressure; D013552:Swine; D014463:Ultrasonography; D001743:Urinary Bladder / Q000000981:diagnostic imaging* / Q000187:drug effects / Q000502:physiology*; D055815:Young Adult