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thewyrdguy

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From: Europe

Joined: 2017-02-19

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Physics of measuring the flow velocity in ultrasound

Hi all,

I know that I am usually that annoying "know it all" guy, but now I have a question. Maybe someone has the answer?

I understand the Doppler effect very well. When (ultra)sound waves are reflected by particles (mostly erythrocytes) that are moving with the blood along the line of propagation of the sound ware, reflected frequency is different from the emitted frequency, and from the difference one can derive the velocity. That is why some instructions state that "you can measure blood stream velocity from the apical view". Quite clear.

But on some machines you can see colour coding of the blood stream on the parasternal view, when the blood is moving perpendicular to the line of wave propagation, like on this picture:

How is it done?