• This report describes a system that allows amplitude information to be used as a third dimension or aspect of display on B-scan ultrasonograms. The relative strength of reflected echoes can be shown on B-scan by means of gray scale, color coding, or on A-scan with amplitude deflection. With this new technique, called isometric display, superimposition of the A-scan trace on the B-scan allows preservation of these amplitude characteristics. The three-dimensional presentation can be rotated around any azimuth to provide isometric viewing of the ultrasonogram. Tissue may then be characterized on a more reliable basis than is permitted by independent analysis of outline and amplitude features.
Coleman DJ, Katz L, Lizzi FL. Isometric, Three-Dimensional Viewing of Ultrasonograms. Arch Ophthalmol. 1975;93(12):1362–1365. doi:10.1001/archopht.1975.01010020984009