Much attention is now being focused on techniques to improve the quality and information content of ultrasonic images of the body. Many of these techniques employ digital pre-processing of coherent echo signals prior to image generation. Examples of these procedures include: resolution enhancement; contrast enhancement (using frequency-domain techniques) to suppress speckle; and imaging of spectral parameters (which sense the sizes and concentrations of sub-resolution tissue constituents). Combinations of spectral parameters and ancillary clinical data (e.g., PSA blood levels) are also being used with statistical classifiers (e.g., discriminant analysis neural network) to generate color-coded, images that indicate tissue type (e.g., cancer) or tissue regions responding to therapy. Sets of these images, obtained from serial-plane scans, promise to be particularly useful when presented in interactive three-dimensional (3-D) formats.