Question

How is the doppler effect used in an ultrasonography diagnostic?

Answer 1

The Doppler effect can be used to determine the velocity of a source of waves.

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In Doppler ultrasound imaging (sonography) pulses of ultrasound are aimed at an artery. Those pulses reflect off of blood cells. The moving cells can be treated as moving sources of the reflected pulses. Upon reflection at the cells a shortening of the wavelength occurs.

The Doppler equation is: `(Delta lambda)/lambda_0=v/c`
`Delta lambda` is the change in wavelength.
`lambda_0` is the original wavelength of the ultrasound emitted from the transducer.
`v` is the speed of the blood cells.
`c` is the speed of the ultrasound in the medium.

The change in wavelength will be determined from the reflected pulses, thus providing a way of calculating the speed of the blood cells.

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The speed of the blood cells for a patient can then be cross checked against values that are considered to be normal. Circulatory problems can be highlighted and followed up with further diagnostic methods or acted upon. Or they may be ruled out by the results.