An overview of signal-processing techniques used in the acquisition, display, manipulation, and analysis of echo scan data is presented. The principles of time-gain compensation, selective enhancement, log compression, fill-in interpolation, edge enhancement, image updating, write zoom, gray scale mapping, black/white inversion, freeze frame, frame averaging, read zoom, thresholding, contrast enhancement, filtering, and region-of-interest definition are reviewed. The concept of gray scale mapping, which dictates how the stored scan data are displayed, is explained with many illustrative examples.
