斎藤 繁実

Shigemi SAITO

東海大学海洋学部

School of Marine Science and Technology, Tokai University

キーワード : focused sound, nonlinear acoustics, second harmonic, tissue harmonic imaging

The distortion of waveform and the generation of second harmonics in nonlinearly propagating focused ultrasound are described. The second harmonic forms a narrower beam with a lower side-lobe level than that of the original beam with the fundamental frequency. The second-harmonic component generated in the prefocal region is cancelled by the component generated in the postfocal region. The component generated in the focal region then becomes dominant in the postfocal region, producing a waveform characterized by sharp peaks and dull troughs.