Naslov
Mjerenje protoka okomitog na ultrazvučni snop
(Transit time measurement of flow perpendicular to ultrasound beam)

Autori
Breyer, Branko ; Svilar, Dragoljub

Vrsta, podvrsta i kategorija rada
Radovi u zbornicima skupova, cjeloviti rad (in extenso), znanstveni

Izvornik
6-th World Congress in ultrasound 3-rd World Congress for Sonographers / - Kopenhagen, 1991

Skup
6-th World Congress in ultrasound 3-rd World Congress for Sonographers

Mjesto i datum
Kopenhagen, Danska, 01.09.1991. - 06.09.1991

Vrsta sudjelovanja
Predavanje

Vrsta recenzije
Međunarodna recenzija

Ključne riječi
mjerenje protoka; ultrazvuk
(measurement of flow; ultrasound)

Sažetak
We calculated the autocovariance function of the reflection signal from Poisson distributed scatterers traversing a defined ultrasound beam. For rare scatterers the velocity is simply the quotient of the beam width and the transit time. For high densities the signals overlap, so that the velocity information must be obtained by autocovariance calculation and measurement. For simple system transfer functions like square pulse or double exponential we obtained closed solutions whose zero crossing points, maxima and minima are linearly related to the single event transit time and thus hyperbolically depend on the velocity. By random variable transformation we have shown that the beam profile and parabolic flow profile have the largest weight in the final results for the largest diameter and for the largest velocity respectively. The Nyquist limit of the measurement has been shown to depend on velocity, depth and scatterer density. Since the echoscope transfer function are more complicated than the ones mentioned, we chacked the theory in an experiment where the autocorrelation function of signals obtained from transverse flow of Sephadex spheres in water was measured. The experiments show that the zero crossing and the delay time of the of the autocorrelation function are both proportional to the transit time, i.e. inversely proportional to the velocity.

Izvorni jezik
Engleski

Znanstvena područja
Matematika, Fizika, Elektrotehnika

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