New Method for Blood Flow Measurement

A new method has been published with the potential to bring great benefit to the use of ultrasound in blood-flow measurement.

Physiologically the body is more dependant upon the volume of blood flow than it is upon the peak velocity of that flow. The problem has long been that the most convenient way to measure the blood flow has been through doppler-ultrasound, a method which yields the less-useful maximum velocity. The difficulty comes with the fact that the velocity of blood flow itself varies in a complicated fashion across the diameter of an artery, making it hard to estimate the flow from just this peak velocity.

Most previous assumptions assumed that the blood flow was a parabola, the same shape which would be obtained from a Newtonian fluid flowing slowing in a straight vessel. Unfortunately, blood is not Newtonian, arteries are not cylindrical and the blood flow is pusatile due to the pumping of the heart – all of which make the profile more complex and the estimation less valid.

Within a paper published in the journal Ultrasound in Medicine & Biology a team from Segrate, Italy detail a novel method which is set to greatly enhance the applicability of doppler-ultrasound blood velocities to clinical guidelines. Recognising the importance of a pulsatile flow the work uses the Womersley number, a single value which describes the nature of the pulsatile flow, and to what extent it differs from the parabolic flow. By combining the peak flow and using a predefined Womersley number which takes into account the geometry the paper presents a method based upon CFD to determine the total blood flow. Validation of the new method demonstrated a better estimation than previously possible.

Keep your eyes open for this method which is sure to arise in the next generation of doppler-ultrasound systems. For those who wish to read more about this novel derivation, please refer to the reference below.

Raffaele Ponzini, Christian Vergara, Alberto Redaelli & Alessandro Veneziani. Reliable CFD-based estimation of flow rate in haemodynamics measures. Ultrasound in Biology & Medicine, 32(10) p.p. 1545-1555, 2006.

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