Ultrasound Image Enhancement Using Discrete Wavelet Transform based on Image Sharpening Model

Ultrasound imaging is one of the most widely used and important diagnostic tools in today's sophisticated medical diagnostics [1]. Ultrasound imaging is becoming more popular day by day because it is relatively inexpensive and portable, especially when compared with other imaging techniques such as MRI and computed tomography (CT), PET [2], [3]. It has no known long-term side effects and rarely causes any discomfort to the patient. It is used to visualize muscles and many internal organs, their size, structure and any pathological injuries with real-time topographic images of the human body without exposing the patient to any radiations. It is also used to visualize a fetus during routine and emergency prenatal care. It provides live images, where the operator can select the most useful section for diagnosing, thus facilitating quick diagnosis. But it is not possible because US image qualities are often deteriorated by noise and other data acquisition devices, illumination conditions, etc. So we have to take a targets of medical image enhancement are mainly to solve problems of low contrast and the high level noise of a medical image [4][5]. Image sharpening is one of several steps which enhances both the intensity and the edge of the images in order to obtain the perceive image. The step helps increase the resolution, the detail, as well as the sharpness of the image. In this paper, methods of image enhancement based on discrete wavelet transform were proposed. However, we cannot obtain more high-frequency information only through discrete wavelet transform. An image’s different scale detail information can be obtained through wavelet transform, but there will be some high-frequency information hidden in high-frequency sub-images of wavelet transform [6][7]. If we decompose these highfrequency sub-images, we can obtained more image high-frequency information which can help us to enhance a US image effectively. Also, we can obtain a better enhancement image if we use both spatial field and transform field procession to enhance an image [10][11]. In addition, we should remove or reduce noise for the reason that there are lots of noises in high-frequency sub-images. For this we proposed a technique which is used to enhance a US image based on discrete wavelet transform, threshold, and linear contrast stretch and edge detection [12][13]. The paper is arranged as follows: section I included the introduction and section II included the algorithm of the proposed scheme is explained with many details and Section III included the results and Analysis. Conclusions are shown in Section IV. Abstract: Ultrasound (US) imaging is a widely used and safe medical diagnosis technique, due to its safe noninvasive nature, low cost, capability of forming real time imaging and continuing improvement in image quality. The usefulness of US imaging is degraded by the presence of signal dependence noise known as speckle noise. Speckle degrades the target detectability in ultrasound images and reduces contrast, resolutions which affect the human ability to identify normal and pathological tissue. The proposed method is for enhancing and sharpening Ultrasound images. By using the discrete wavelet transforms (DWT) flowed by using the linear contrast stretching technique and sobel operator to obtain the enhanced image. Firstly, we use discrete wavelet transform to decompose the input image and then apply soft threshold in decomposition section that concentrates on denoising each subband (except lowest coefficient subbands) by minimizing insignificant coefficients and adapt with modified coefficients which are significant and more responsible for image reconstruction. Finally, use image sharpening model that is based on linear contrast stretching and edge detection with sobel operator to get the enhanced image. This proposed method satisfy the human visual quality and preserve its edge features effectively.