### ASA 130th Meeting - St. Louis, MO - 1995 Nov 27 .. Dec 01

## 4pSP8. Acoustic imaging with radiation imaging operators.

**Mohammed I. Raza
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*Dept. of Elect. Eng., Univ. of Missouri-Rolla, Rolla, MO 65401
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**Richard E. DuBroff
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Thomas J. Herrick
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*Univ. of Missouri-Rolla, Rolla, MO 65401
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A differential operator has been formulated, which can be used to remotely
detect boundaries and position of objects from remote data. The operator has
been called the radiation imaging operator (RIO). The RIO is composed of local
characteristic parameters and local derivatives of the acoustic wave. After
operating on the wave distribution, the output gives a minimum at the boundary
of the object, when the correct values of the characteristic parameters are
used. The RIOs are developed from radiation boundary conditions (RBCs) and the
relevant material boundary conditions (MBCs). The RBCs were formulated [B.
Engquist and A. Majda, Math. Comput. 31, 629--651 (1977)] to simulate the
propagation of out-going waves without any significant reflection at the
truncating boundary. The MBCs are in the form of Dirichlet and Neumann boundary
conditions. A finite-difference time-domain algorithm is implemented to image
objects using the discretized RIO, where the shape and location of object is not
known. The imaging technique has been found to be robust and tolerant to a
reasonable amount of noise.