Processing and Analysis of Ultrasound Images for Tissue Characterization

Abstract

Medical imaging is a non-invasive process of visualizing the inner body tissues, organs and bones for diagnosis purpose. It is the fast growing branch of biomedical engineering. These days many imaging modalities are available for different applications. Ultrasound imaging is the most popular because it is non-ionizing, low cost, portable and real time imaging. The main applications of ultrasound imaging are visualizing the fetus development, diagnosis of prostrate and abdominal organs like kidneys, gallbladder and liver. Liver is one of the most important organs in the human body, because it controls many important metabolisms. Fatty liver disease (steatosis) is highly prevailing disease among all the liver diseases in India. The visual examination of ultrasound images, for diagnosis of fatty liver is subjective and less accurate in marginal cases. Fatty liver is a condition that occurs when the fat content of the hepatocytes increases, resulting in variation of the texture of liver surface. Therefore, quantitative texture analysis may give crucial information which is otherwise difficult to extract by visual interpretation of ultrasound images. In this research work, a Computer Aided Diagnostic (CAD) method is proposed for the liver tissue characterization using texture analysis. The ultrasound imaging has one limitation, and that is speckle, which degrades the visual quality of ultrasound images and masks some fine details of tissue under observation. Therefore it is important to suppress this speckle before any computer aided image processing or analysis, while keeping the diagnostic information intact. To accomplish this task, a modified fourth order partial differential equation (fpde) based filter is proposed, which is adaptive to local coefficient of variance in the 3x3 spatial window. To further increase the efficacy of the filter, edge-map technique is used, which enhances the edges and fine details in the ultrasound image.