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Use of Nakagami Statistics and Empirical Mode Decomposition for Ultrasound Tissue Characterization by a Nonfocused Transducer |
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| Authors: | Po-Hsiang Tsui Chien-Cheng Chang Ming-Chih Ho Yu-Hsin Lee Yung-Sheng Chen Chien-Chung Chang Norden E Huang Zhao-Hua Wu King-Jen Chang |
| Institution: | ∗ Division of Mechanics, Research Center for Applied Sciences, Academia Sinica, Taipei, Taiwan, ROC;† Institute of Applied Mechanics, National Taiwan University, Taipei, Taiwan, ROC;‡ Department of Surgery, National Taiwan University Hospital and College of Medicine, National Taiwan University, Taipei, Taiwan, ROC;§ Angiogenesis Research Center, National Taiwan University, Taipei, Taiwan, ROC;¶ Department of Electrical Engineering, Yuan Ze University, Chung Li, Taiwan, ROC;# Research Center for Adaptive Data Analysis, National Central University, Chung Li, Taiwan, ROC;∗∗ Department of Meteorology, Florida State University, Tallahassee, FL, USA |
| Abstract: | The Nakagami parameter associated with the Nakagami distribution estimated from ultrasonic backscattered signals reflects the scatterer concentration in a tissue. A nonfocused transducer does not allow tissue characterization based on the Nakagami parameter. This paper proposes a new method called the noise-assisted Nakagami parameter based on empirical mode decomposition of noisy backscattered echoes to allow quantification of the scatterer concentration based on data obtained using a nonfocused transducer. To explore the practical feasibility of the proposed method, the current study performed experiments on phantoms and measurements on rat livers in vitro with and without fibrosis induction. The results show that using a nonfocused transducer makes it possible to use the noise-assisted Nakagami parameter to classify phantoms with different scatterer concentrations and different stages of liver fibrosis in rats more accurately than when using techniques based on the echo intensity and the conventional Nakagami parameter. However, the conventional Nakagami parameter and the noise-assisted Nakagami parameter have different meanings: the former represents the statistics of signals backscattered from unresolvable scatterers, whereas the latter is associated with stronger resolvable scatterers or local inhomogeneity caused by scatterer aggregation. (E-mail: mechang@gate.sinica.edu.tw; mcho1215@ntu.edu.tw) |
| Keywords: | Nakagami distribution Empirical mode decomposition Tissue characterization |
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