Abstract

The Study of Acoustic Nonlinearity Parameter Tomography in Reflection Mode

X.F.Gong, Y.S.Yan, D.Zhang, H.L.Wang (State Key Lab of Modern Acoustics, Institute of Acoustics, Nanjing University, China)

e-mail: zligong@nju.edu.cn

The acoustic nonlinear parameter B/A describes the nonlinear features of the finite amplitude wave propagation and can be a new parameter in ultrasound tissues characterization. In this paper, as a new method, the computer tomography(CT) of nonlinearity parameter B/A in reflection mode is proposed. Based on the theory of propagation of reflected second harmonics in the layered medium and the insert-substitution method of finite amplitude sound wave, the computer simulation of nonlinearity parameter tomography from calculated reflected second harmonic data and filtered convolution algorithm used in the conventional CT technique is reported and the images of B/A for several biological specimens are reconstructed. As for the experimental investigation, a compound transducer is used to transmit the fundamental sound wave (2 MHz) and to receive the reflected second harmonics (4 MHz) . The experimental system is presented in this paper. The experimental images of nonlinearity parameter B/A for several biological tissues, including normal and pathological tissues are demonstrated. Results show that this method provides prospective application of nonlinearity partameter tomography in biological diagnosis and industrial nondestructive detection.

Section : 5