RIU 324 Lecture Notes - Lecture 47: Sonographer, Grayscale, Noise Floor
23 Apr 2020
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Performed twice; once by system and cannot be adjusted; second to adjust grayscale. Also called log compression or dynamic range. Dynamic range: narrow dynamic range means fewer choices. Ratio of the largest to smallest signal a system can faithfully represent. Also stated as span of processed signals from lowest to highest. Pixel values translated to shade of gray. Compression is a method to reduce the dynamic range by mapping a larger range of signals into a smaller range of signals. Compression is needed since the dynamic range of the returning echoes is much greater than the dynamic range visible to the human eye. Through compression, the ratio of the maximum to the minimum signals is significantly reduced. Compression in the receiver is not under user control. However, there is more signal compression which takes place in the back end of the system that is under user control. Changing electrical signals into a form more suitable for display.
