Acoustical imaging: from ancient Phoenicians to modern physicians

Ultrasonic energy can produce images not obtainable with any other form of radiation. The human use of sound in imagery is centuries old, and many instruments of great utility have been developed. Pulse-echo, phase-amplitude, and amplitude-mapping approaches constitute the conceptual bases for three fundamental types of acoustic imaging systems. By now, however, systems exist that combine these approaches in ways that make their unambiguous categorization difficult or impossible. These systems frequently employ principles associated with holography, tomography, microscopy, and seismic exploration