title: Use of nakagami statistics and empirical mode decomposition for ultrasound tissue characterization by a nonfocused transducer.
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.
authors.affiliation: Division of Mechanics, Research Center for Applied Sciences, Academia Sinica, Taipei, Taiwan, ROC.
authors.forename: Po-Hsiang
authors.initials: PH
authors.lastname: Tsui
authors.forename: Chien-Cheng
authors.initials: CC
authors.lastname: Chang
authors.forename: Ming-Chih
authors.initials: MC
authors.lastname: Ho
authors.forename: Yu-Hsin
authors.initials: YH
authors.lastname: Lee
authors.forename: Yung-Sheng
authors.initials: YS
authors.lastname: Chen
authors.forename: Chien-Chung
authors.initials: CC
authors.lastname: Chang
authors.forename: Norden E
authors.initials: NE
authors.lastname: Huang
authors.forename: Zhao-Hua
authors.initials: ZH
authors.lastname: Wu
authors.forename: King-Jen
authors.initials: KJ
authors.lastname: Chang
mesh_terms: D000465:Algorithms; D000818:Animals; D003627:Data Interpretation, Statistical; D007089:Image Enhancement / Q000379:methods; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D008099:Liver / Q000000981:diagnostic imaging*; D008103:Liver Cirrhosis / Q000000981:diagnostic imaging*; D051381:Rats; D017208:Rats, Wistar; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D014463:Ultrasonography / Q000379:methods*