Good images have been obtained from several different approaches to real‐time acoustic imaging, including approaches involving the following three phenomena: static‐ripple diffraction, dynamic‐ripple diffraction, and Bragg diffraction. Using threshold acoustic contrast as the basis of comparison, this paper examines analytically these three approaches and compares their sensitivities with those of another category of systems whose operation utilizes fundamental scanning modes. The analyses are based on idealized models where only the most fundamental noise is considered. The threshold contrasts are shown to vary in different ways with various system parameters. A nonexisting, hypothetical system, which is the best theoretical candidate among the fundamental scanning systems, is selected as the reference of comparison. For a set of consistent operating conditions compatible with the application of medical diagnosis, calculation shows that the inherent capabilities of the three systems involving, respectively, the three above‐mentioned phenomena are of the same order. However, the inherent capability of the hypothetical reference system is considerably better. The other members of the category of fundamental scanning systems, although theoretically less advantageous than the hypothetical reference system, also enjoy advantages in terms of ultimate sensitivity.

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