吉田 千秋¹, 中島 真人¹, 油田 信一²

Chiaki YOSHIDA¹, Masato NAKAJIMA¹, Shin-ichi YUTA²

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

¹Department of Electrical Engineering, Faculty of Science and Technology, Keio University, ²Institute of Information Science and Electronics, The University of Tsukuba

キーワード : Speckle, Compound scan, Signal processing

　Ultrasound B-mode imaging in the diagnosis is available for wide regions and has the advantage of real time property. Unfortunately speckle appears in the B-mode images, and this is the major factor for image quality degradation. Speckle is caused by the interference of returning waves, and is not coincide with the micro-structure of tissues. Random speckle noise is reduced by adding up weak cross-correlated images. These images are produced by using the spatial compound scan or the frequency compound scan. The phased array electronic scan realize a high speed compounding, but the frame-to-frame time increases for compounding. Accordingly, the compound scan is not so effective for real time speckle reduction.
　In this paper, we propose real time method for reducing speckle noise with the spatial compounding and with the simple signal processing. The processing leads the echo signal to band-pass filters arranged in a raw, and produces weak cross-correlated signals, which are added up after envelope detection to carry out equivalently the frequency compounding. Accordingly, a number of images can be added up for speckle noise reduction in the proposed method.
　We carried out computer simulations designed for strict consideration of the pulse ultrasound field. The results show that the method is available for speckle noise reduction. Furthermore, experimental results show that the method is not interfered by electric noise, ultrasonic attenuation and multiple scattering.