Liver Fibrosis Assessment Using Ultrasound Backscattering Dynamics Statistical Parametric Imaging Index
| Autor: | Sheng-Hsiang Chuang, 莊勝翔 |
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| Rok vydání: | 2011 |
| Druh dokumentu: | 學位論文 ; thesis |
| Popis: | 99 This study is dedicated to the application of liver fibrosis assessment using ultrasound imaging, focusing on the envelope signal converted from RF signal to investigate the differences of the statistical distributions between healthy and disease livers. Liver cirrhosis is considered as an irreversible process that there is almost no effective course of treatment to recover the fibrosis liver. Fibrosis is marked by the gradual replacement of hepatocytes by extracellular collagen, which is a chronic and long-term degeneration of the liver function. Invasive assessment like liver biopsy often accompanied with sequela and is prone to sampling error when small biopsy samples are analyzed. Therefore, there is a clinical need to establish an effective and reliable method for the noninvasive assessment, espesically the prediction of early stage liver fibrosis. Ultrasound speckle in B-mode images, which is the result of a wave interference phenomenon of backscattering signal, has been used for clinical liver fibrosis and steatosis diagnosis. The characteristic of speckle is associated with the density of scatterers in tissue, indicating different patterns among various tissue properties. To analyze the RF signal derived from liver ultrasound, three methods were implemented: Nakagami-m parameter method, Yamaguchi method and ACRA (adaptive criteria-referenced assessment) method. Nakagami-m parameter method uses m-value to describe the distribution within the ROI (region of interest), proved to be a valid approach characterizing breast tumors and cataract lens. Yamaguchi method determines whether the ROI is a fiber area or not based on the assumptive parameters derived from the phantom experiment. ACRA is a method, which was originally developed by our lab and could be adapted to various system conditions; it reflects the degree of fibrosis liver via the unassessed tissues in comparison with a criteria-reference constructed by healthy tissues. Results showed that Nakagami-m and ACRA method were able to discriminate the degree of fibrosis from livers in vitro rat experiment. Area under receiver operating characteristic curve (AUC) was used to judge the performence. In the in vivo linear array experiment, three methods performed well in the early stage F≥1 fibrosis (Nakagami-m: 0.86, Yamaguchi: 0.98, ACRA: 0.95). In the in vivo convex array experiment, three methods performed well in the stage F≥1 and F≥2 fibrosis (Nakagami-m: 0.96, 0.82, Yamaguchi: 0.93, 0.92, ACRA: 0.99, 0.93). In the in vitro operation linear array experiment, only ACRA successfully identified stage F≥2 and F=4. It is concluded that the concept of ACRA could exend to other domains, observing the degree of the difference between tissues to indicate the abnormity. This method possesses clinical potential and application value. |
| Databáze: | Networked Digital Library of Theses & Dissertations |
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