The ultrasound attenuation coefficient is known to increase with frequency for soft biological tissue within the diagnostic frequency range. The frequency dependent attenuation coefficient becomes an important parameter in the field of clinical tissue characterization, especially in liver, and the ultrasonic quantitative B-scan imaging. But, because of the low S/N ratio, the estimator variance becomes very large. Henceforth, it has been a difficult problem to estimate the attenuation slope from the backscattered ultrasound signal.
This thesis suggests a new ultrasound attenuation estimator based on the calibrated log spectral difference. The proposed estimation process consists of Wiener filtering, Kalman filtering and median filtering. The simulation results and experiment on tissue equivalent(TE) phantom shows that combination of the filterings has a better performance with a considerably reduced estimator variance than the conventional estimator.
diagnostic 주파수 영역에서 주파수에 따라 증가하는 특성을 갖는 초음파의 감쇄계수 측정은 간의 상태를 파악하는 diagnostic 응용분야와 정량적인 B-Scan 영상에서 중요한 parameter가 되는데 본 논문에서는 LMSE 필터와 median 필터를 이용한 새로운 앨고리즘을 제안하여 기론의 다른 앨고리즘과 비교하여 보다 좋은 performance 를 갖음을 simulation 과 실험으로 부터 보여주었다.
