大矢 晃久¹, 油田 信一², 島崎 通³, 中島 真人¹

Akihisa OHYA¹, Shin'ichi YUTA², Tohru SHIMAZAKI³, Masato NAKAJIMA¹

¹慶応義塾大学理工学部電気工学科, ²筑波大学電子情報工学系, ³横河メディカルシステム（株）

¹Department of Electrical Engineering, Faculty of Science and Technology, Keio University, ²Institute of Information Science and Electronics, University of Tsukuba, ³Yokogawa Medical Systems, Ltd.

キーワード : Speckle reduction, Spatial compounding, Sector scan

The ultrasonic B-mode image is degraded by a random granular pattern called “speckle”. This speckle arises as a result of random interference of the ultrasonic waves being reflected or scattered from each point of the tissue and does not coincide with the microstructure of the tissue itself. It is known that the speckle is well reduced by means of the spatial compounding process. But in fact, the practical system for this process has conventionally been large-scale.
On the contrary, we have devised a compact spatial compounding system using plural sector scan-type transducers. In this paper, we investigate the scheme of the system, the effectiveness of speckle reduction, and the resolution of the system by 2-D computer simulations. The results of experiments using an agar phantom including powdered graphite are also shown.
We conclude that the speckle is sufficiently reduced without degradation of the resolution when using three sector scan-type transducers whose mutual intervals are more than 10 millimeters each. By using the sector scan-type transducers in this system, the size of the probe can be made equal to the electric linear scan probe, which is the most widely used type. Consequently, we believe that this system is particularly effective in making diagnoses in the abdominal region, the mammary gland and the thyroid gland.