河原 淳平¹, 八木 晋一³, 中山 淑¹, 秋本 伸²

Jumpei KAWAHARA¹, Shin'ichi YAGI³, Kiyoshi NAKAYAMA¹, Shin AKIMOTO²

¹上智大学理工学部電気電子工学科, ²東京女子医科大学消化器病センター外科, ³明星大学理工学部電気工学科

¹Department of Electrical & Electronics Engineering, Faculty of Science & Technology, Sophia University, ²Division of Surgery, Institute of Gastroenterology, Tokyo Women's College of Medicine, ³Doparment of Electrical Engineering, Faculty of Science & Technology, Meisei University

キーワード : Short-time spectral moment, Backscattring coefficient tomography, Attenuation correction

We present a quantitative backscatter imaging method in this report. It is based on an estimation of the turn around attenuation from the centroid frequency of an r-f echo under the appropriate assumptions of backscattering frequency characteristics and the assumed frequency proportional attenuation characteristics. R-f echo data from a conventional B-mode system is digitized with 10-bit resolution. The data acquisition rate is 0.5 sec/frame. The overall system characteristics, including the so-called beam diffraction effect, are calibrated using a stirred dextran particle suspension with a known backscattering coefficient as a phantom. From this calibration data, time-varying gaussian-shaping filtering data is calculated to shape the system transfer function to gaussian spectral form everywhere in the viewing area. The in-vivo echo data is first processed with this time-varying shaping filter, and the short time spectral moments are estimated from the derivatives of the analytic signal of the processed echo deta. The attenuation correction term is calculated from the normalized first moment, and the backscattering coeficient image is finally obtained, the data thus obtained from the normal and pathological livers was in agreement with the reported in-vitro data.