Basic study on velocity-flow urodynamics using Doppler sonography: simultaneous detection of cavitation and Doppler signals in an artificial urethral model.
BACKGROUND
We have developed velocity-flow urodynamics using Doppler sonography based on the hypothesis that microbubbles formed in the urethra are responsible for Doppler signals. In order to confirm this hypothesis derived from Bernoulli's principle, we investigated the simultaneous detection of cavitation noise and Doppler signals in an experimental system.


METHODS
An experimental circuit was built in which a stenosis was created using a glass or silicon tube with tap water used as the sample fluid. Doppler signals, pressure before and after the stenosis, flow rate, flow velocity and cavitation noise were measured. Direct detection of cavitation with a high-speed charged-coupled device (CCD) camera was conducted in the glass tube. The relationship between cross-sectional area and flow velocity in terms of the detection of Doppler signals was analyzed in the silicon tube study.


RESULTS
In the glass tube study, a high-speed CCD camera clearly detected masses of microbubbles associated with cavitation. The range of flow rates creating cavitation completely corresponded with those producing Doppler signals detected by ultrasonography. A similar correlation was observed in the silicon tube study, which showed that a low flow velocity of 41.5 cm/sec through a stenosis with a cross-sectional area of 20 mm(2) created Doppler signals at a flow rate of 8.3 mL/sec.


CONCLUSIONS
The results of the present study confirmed that microbubbles created in flowing urine are responsible for Doppler signals. Measurement of velocity-flow urodynamics has great potential to become a non-invasive and reliable alternative to conventional pressure- flow urodynamic studies.
Kumon
Hiromi
H
Department of Urology, Okayama University Graduate School of Medicine and Dentistry, Okayama 700-8558, Japan. kumon@md.okayama-u.ac.jp
Ozawa
Hideo
H
Nose
Hiroyuki
H
Ohta
Hidekuni
H
Nishigaki
Kazu
K
D006801:Humans; D008365:Manometry; D045423:Microbubbles; D008954:Models, Biological; D012212:Rheology / Q000379:methods*; D018608:Ultrasonography, Doppler; D014521:Urethra / Q000502:physiology*; D014563:Urodynamics / Q000502:physiology*