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Factors Affecting Color Flow Images: Color Gain

You can adjust the amount of color in an image using the color gain control. A properly adjusted color gain control lets you see all the available color information. Selecting a color gain setting that is to low prevent detection and display of low amplitude signals. Blood flow patterns appear smaller than they really are since the lows amplitude signals, at the edges of the jet, are not visible.

Image A Image B

Image A demonstrates the optimum gain setting. Image B is the same patient with a lower gain setting. Selecting a color gain setting that is too high causes color “noise.” Noise is the term for very low amplitude signals that are usually below the flow detection threshold. Increasing the gain increases the amplitude of these signals, raising them above the flow detection threshold. These color noise signals appear as random multicolored speck overlaying the blood flow in the chambers. To set color gain correctly; increase the gain until you see obvious color noise. Then, decrease the color gain to the point where the noise just begins to disappear. Note: Excess color gain can introduce variance-like color artifacts; in the same way that excess spectral Doppler gain can cause spectral broadening.