Effect of beam width on quantitative estimation of liver fibrosis using ultrasonic images

In order to realize a quantitative diagnosis of liver fibrosis, we have been developing a method of quantitatively evaluating liver fibrosis. In our previous study, we were able to estimate fibrosis parameters relatively well. However, we found that, in the initial stage, the estimated values in the evaluation of liver fibrosis deviate from their true values in certain tendencies. As one of the reasons for this deviation, it is considered that the region of fibrotic tissues spreads in an ultrasonic image owing to the effect of the ultrasonic beam width. In this paper, we present the simulation method of evaluating the effect of the ultrasonic beam width for the quantitative estimation of liver fibrosis. Owing to the effect of the ultrasonic beam width, the estimated amount of fibrotic tissue becomes larger than its true value when the fiber width becomes smaller. The estimated fibrosis parameters cannot be estimated stably when the fiber width becomes smaller than about one-half of the ultrasonic beam width.