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The dynamic range control functions as a contrast control, allowing the sonographer to change the range of echo signal strengths that are displayed as different shades of gray on the monitor.
Function and Purpose
Ultrasound transducers detect a very wide range of echo signal strengths (amplitudes) from different tissues, from very strong reflections (like bone) to very weak reflections (like the internal texture of soft organs). However, the monitor can only display a much narrower range of brightness levels. The dynamic range control (sometimes labeled as "Compression") reduces this wide range of received signals into the displayable gray scale range, ensuring that details are visible without the strongest signals appearing as pure white and the weakest as pure black.
An example of the Dynamic Range control knob on a GE Logiq machine
Adjusting the dynamic range changes the visual appearance and contrast of the image:
High (Wide) Dynamic Range:
The image will have more shades of gray, resulting in a smoother, softer look with lower contrast. This setting is beneficial for examining homogenous tissues, such as the liver or thyroid, where subtle differences in tissue texture need to be distinguished.
Low (Narrow) Dynamic Range:
The image will have fewer shades of gray and appear more black and white, resulting in higher contrast with sharper, more defined edges.
This setting is often preferred for vascular or echocardiography work to make fluid-filled cavities (like blood vessels) appear truly anechoic (black), which helps in clearly delineating vessel walls or identifying specific structures.
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