油田 信一¹, 是久 充郎^{2, 3}, 渋谷 昇², 伊藤 健一², 横井 浩⁴

Shinichi YUTA¹, Mitsuo KOREHISA^{2, 3}, Noboru SHIBUYA², Kenichi ITO², Hiromu YOKOI⁴

¹筑波大学電子情報工学系, ²東京農工大学工学部電子工学科, ³現在,日本電気, ⁴日生病院

¹Inst. Electronics and Information Sciences, University of Tsukuba, ²Dept. Electronic Engng., Tokyo Univ. of Agr. and Tech., ³Now, with Nippon Electric, ⁴Nissei Hospital

キーワード : image processing, artifacts by sidelobes

　The artifact or the ghost images caused by the grating lobes of the ultrasonic beams in the electro-scanning ultrasonic diagnostic equipment is treated, to get the image processing method by the computers for its reducing. The artifacts by grating lobes is the exclusive problem in electro-scanning equipment and there is no problem in the traditional single probe systems.
　First, the principle of generation and the property of the ghost images is discussed. In the case of the point target, the observed ghost images appears on the hyperbora whose peak is at the real image point. Next, The simple image processing algorithm to obtain the real image from the observed image is got under the assumption as follows ;
　(1) the characteristics in the reflection of ultrasonic beam at the object is constant independently for the angle of incidence,
　(2) the power of observed echo signals becomes the sum of the each echo powers by the main-lobe and the grating-lobes.
　This image processing is an approximated method. However, the resultant of processing in the experimental example using the sponge phantom is relatively good.