Texture analysis of ultrasound liver images with contrast agent to characterize the fibrosis stage

The present work proposes to identify the liver fibrosis stage from a characterization of the perfusion using ultrasound images. A liver disease leads to changes in the organ perfusion that can be emphasized on ultrasound images by injecting contrast agent. In the evolution of the disease, 5 stages are usually defined and a visual evaluation of these stages is often difficult. We propose to characterize the evolution of the perfusion when the contrast agent is injected from image texture analysis and ultrasound tissue characterization techniques. To validate this approach, a set of 18 sequences of liver images at different pathological stages is used. The sequences represent at the beginning the liver without contrast agent and about 20 s later the contrast agent is fully distributed in the tissue. A window of homogeneous tissue is extracted each second for processing. 38 features were involved in the statistical analysis. The results show that the texture analysis of images corresponding to the fully distributed contrast agent is more relevant to identify the stage of fibrosis than the features characterizing the evolution of the texture. In particular, a classification of the samples in two classes (the 2 highest pathological grades versus the 3 lowest) exhibits a sensitivity of about 80 % and a specificity of about 60 %. The statistical significance was set to p<0.05.