A method for imaging nonlinear parameter of a body tissue using 2nd harmonic in the echo signals has been proposed by Akiyama et al.. To eliminate the effects of attenuation and scattering of tissue, the 2nd harmonic is divided by the fundamental when ultrasuond of double frequency are transmitted. However, in the case where the bands of the fundamental and the 2nd harmonic components are overlapped in frequency domain, it is impossible to completely separate both the components. In addition, the scattering effect is removed, to thereby weaken the structural expression of the tissue in the image. To solve the problems, this paper uses the technique proposed by Kamakura et al. to accurately detect the fundamental and the 2nd harmonic components. This paper also uses the transmission pulses including both of two fundamental components of frequency f{sub}1 and 2f{sub}1. Further, the scattering information of a membrane or a valve that induces strong echo is preserved for each ultrasonic beams, and the images in which the structural information of the body tissue remains are obtained.
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