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What is Colourflow duplex ultrasound imaging?
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What is Colourflow duplex ultrasound imaging?
 Colourflow duplex scanning is non-invasive and entirely pain-free, allowing real-time imaging of arteries and veins with an assessment of the direction and speed of blood flow.
Three types of ultrasound are used:
Greyscale ultrasound imaging
Ultrasound is reflected to varying degrees depending on the nature of the tissue. In general, ultrasound passes through fluids giving a ‘black’ appearance but different tissues reflect ultrasound giving different shades of grey. Artery disease is easily seen as grey narrowing within the blood stream, which appears as a black channel.
Colourflow Doppler ultrasound mapping
Sophisticated software is used to generate a real-time representation of blood flow as a range of colours, which overlay the greyscale image. Blood flowing towards the probe is usually shown as red (arteries), and away from the probe as blue (veins).
Image showing directional flow an artery (red) and vein (blue) and a normal Doppler spectral trace.
Colourflow can show an increase in the speed of blood flow by a change in the colour shade. Very fast and turbulent blood flow is usually seen as a mosaic of colours.
Image above shows the greyscale within the blood flow and colourflow change at a severe stenosis.
Pulsed Doppler ultrasound
An ultrasound beam can be used to produce a spectral waveform, which accurately measures the speed and direction of blood flow.
As blood passes through a narrowing in an artery the blood velocity increases.
The image above shows the change in velocity of flow in a severe stenosis.
This increase in velocity is directly related to the severity of narrowing (stenosis) and can be used to identify significant arterial disease non-invasively.
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