Nonlinear Image Enhancement by Self-Adaptive Sigmoid Function

Abstract

Nonlinear imaging is more sensitive to changes in components, structure and pathological state of a tissue in comparison with the traditional ultrasound imaging. However, in view of the particularity of nonlinear imaging, the contrast of an image is generally very low and thus a doctor cannot clearly distinguish distribution of nonlinear parameters clearly. Therefore, the paper aims to design a self-adaptive sigmoid function to enhance the original nonlinear image. First of all, we needed to find an interesting area which included the different nonlinear acoustic parameters according to harmonic energy. Next, then the histogram of ROI was analyzed to obtain two parameters of sigmoid function values, and the contrast of the image was increased prominently by this method. At last, the contrast to noise ratio (CNR) was calculated to prove that the contrast of the image which was enhanced by this method improved by 5 times in comparison with the raw nonlinear image.