大川井 宏明, 田中 元直

Hiroaki OHKAWAI, Motonao TANAKA

東北大学抗酸菌病研究所

Research Institute for Chest Diseases and Cancer, Tohoku University

キーワード : interference, reflection coefficient, transmission coefficient, thin biological tissue layer, tissue characterization

It is known that the reflected and transmitted waves are affected by the interference when ultrasonic wave insides to a thin layer. However, in the case where the difference of acoustic impedances of each medium is throughly small, such as biological tissues, the interference phenomena produces variations in the reflected wave, while its effect is small enough to be ignored in the transmitted wave.
Above phenomena were theoretically proved for the reflection and transmission coefficients. The constants used about biological tissues are obtained experimentally. In application of this theory to the pulse echo method, the wave reflected from a thin biological tissue layer, affected by the interference, would give information of region of reflection considerably, because it is not affected by interference in the propagation path. Therefore, though the echo displayed in a conventional ultrasonic diagnosis equipment is obtained by the envelope detection, it considerably has the information of the displayed area for some tissue characterization.