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Noninvasive Evaluation of Bladder Wall Mechanical Properties as a Function of Filling Volume: Potential Application in Bladder Compliance Assessment.

Nenadic I, Mynderse L, Husmann D, Mehrmohammadi M, Bayat M, Singh A, Denis M, Urban M, Alizad A, Fatemi M - PLoS ONE (2016)

Bottom Line: 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.The ex vivo studies showed a high correlation between the UBV parameters and direct pressure measurement (R2 = 0.84-0.99).The results of UBV on healthy volunteers, performed without catheterization, were comparable to a compliant bladder patient.

View Article: PubMed Central - PubMed

Affiliation: Department of Physiology and Biomedical Engineering, Mayo Clinic College of Medicine, Rochester, Minnesota, United States of America.

ABSTRACT

Purpose: 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.

Materials and 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.

Conclusion: 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.

No MeSH data available.


Related in: MedlinePlus

Diagram of the in vivo patient studies depicting the concurrent UDS cystometry and UBV measurements, where Pves = vesical pressure, Pabd = abdominal pressure, and Pdet = Pves−Pabd = detrusor pressure.
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pone.0157818.g003: Diagram of the in vivo patient studies depicting the concurrent UDS cystometry and UBV measurements, where Pves = vesical pressure, Pabd = abdominal pressure, and Pdet = Pves−Pabd = detrusor pressure.

Mentions: Fig 3 depicts the concurrent UBV and UDS measurement procedure in our 2 patient studies. In UDS, one pressure sensor was inserted into the patient’s bladder and another into the rectum (or vagina). The difference in the pressure between the two sensors was used to calculate the detrusor pressure across the bladder wall. Saline was infused into the bladder through the catheter in volume increments. At each volume increment, detrusor pressure was recorded along with UBV measurements. The bladder wall was identified manually on the B-mode and targeted for focusing the push beam using an ultrasound system (Verasonics, Redmond, WA) equipped with a curved linear array (C4-2, ATL/Philips, Bothell, WA) whose center frequency is 2.5 MHz. An ultrasound toneburst 600–900 μs in duration was used to create the ARF beam to excite mechanical waves in the bladder wall. Plane wave imaging with a three-angle coherent angular compounding was used to track the wave propagation in the bladder wall [18]. Plane waves were transmitted with a pulse repetition frequency of 2.5 kHz at a center frequency of 3.0 MHz. The duration of the toneburst was chosen to create enough tissue motion. The imaging frame rate provided sufficient samples for continuous tracking of the induced Lamb waves up to 500Hz. The UBV data acquisition was approximately 100 ms; thus multiple acquisitions/volume could be acquired in less than a minute. The processing results were highly reproducible as the bladder wall was identified by a sonographer with more than 20 years of experience. All imaging and processing parameters were fixed for different patients to avoid retrospective tuning and calibrations.


Noninvasive Evaluation of Bladder Wall Mechanical Properties as a Function of Filling Volume: Potential Application in Bladder Compliance Assessment.

Nenadic I, Mynderse L, Husmann D, Mehrmohammadi M, Bayat M, Singh A, Denis M, Urban M, Alizad A, Fatemi M - PLoS ONE (2016)

Diagram of the in vivo patient studies depicting the concurrent UDS cystometry and UBV measurements, where Pves = vesical pressure, Pabd = abdominal pressure, and Pdet = Pves−Pabd = detrusor pressure.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4920425&req=5

pone.0157818.g003: Diagram of the in vivo patient studies depicting the concurrent UDS cystometry and UBV measurements, where Pves = vesical pressure, Pabd = abdominal pressure, and Pdet = Pves−Pabd = detrusor pressure.
Mentions: Fig 3 depicts the concurrent UBV and UDS measurement procedure in our 2 patient studies. In UDS, one pressure sensor was inserted into the patient’s bladder and another into the rectum (or vagina). The difference in the pressure between the two sensors was used to calculate the detrusor pressure across the bladder wall. Saline was infused into the bladder through the catheter in volume increments. At each volume increment, detrusor pressure was recorded along with UBV measurements. The bladder wall was identified manually on the B-mode and targeted for focusing the push beam using an ultrasound system (Verasonics, Redmond, WA) equipped with a curved linear array (C4-2, ATL/Philips, Bothell, WA) whose center frequency is 2.5 MHz. An ultrasound toneburst 600–900 μs in duration was used to create the ARF beam to excite mechanical waves in the bladder wall. Plane wave imaging with a three-angle coherent angular compounding was used to track the wave propagation in the bladder wall [18]. Plane waves were transmitted with a pulse repetition frequency of 2.5 kHz at a center frequency of 3.0 MHz. The duration of the toneburst was chosen to create enough tissue motion. The imaging frame rate provided sufficient samples for continuous tracking of the induced Lamb waves up to 500Hz. The UBV data acquisition was approximately 100 ms; thus multiple acquisitions/volume could be acquired in less than a minute. The processing results were highly reproducible as the bladder wall was identified by a sonographer with more than 20 years of experience. All imaging and processing parameters were fixed for different patients to avoid retrospective tuning and calibrations.

Bottom Line: 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.The ex vivo studies showed a high correlation between the UBV parameters and direct pressure measurement (R2 = 0.84-0.99).The results of UBV on healthy volunteers, performed without catheterization, were comparable to a compliant bladder patient.

View Article: PubMed Central - PubMed

Affiliation: Department of Physiology and Biomedical Engineering, Mayo Clinic College of Medicine, Rochester, Minnesota, United States of America.

ABSTRACT

Purpose: 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.

Materials and 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.

Conclusion: 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.

No MeSH data available.


Related in: MedlinePlus