Nonlinear characteristics of the acoustic propagation of ultrasonic waves and mechanical vibrational response of structures inside the medium are explored as a device for imaging at frequencies on the order of kilohertz (kHz), from the excitement with ultrasonic waves in order of megahertz. The sound emitted from the interaction of ultrasonic wave to the region of interest is acquired and processed to assign each small portion of the tissue response acoustic spectral characteristics of their mechanical structure.

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