The Notion Of Nonstationary Degree And Its Application On Ultrasonic Image Of Common Carotid Artery

As the development of the technique of medical radiology in recent years, with good qualities, like safety, fast speed, real time and low price, the ultrasound medical image technology has taken great effect on many aspects, such as medical diagnose. At the same time, the average age of the whole society becomes older. The health of the old people attracts many people's attention. The most lethiferous disease for these people is cardio-cerebrovascular disease. Moreover, the pathological basis of such disease is atherosclerosis, which could be diagnosed and preventive through ultrasound imaging. However, Comparing ultrasonic image (US) with other imaging technology, the quality of the ultrasonic image is not very well for plenty of noise. It is hard for a doctor to check the tissue of common carotid artery and diagnose illness exactly. Since then, the enhancement of ultrasound image has become a very important and challenge project in image processing. Many researchers put forward many algorithms to enhance the ultrasound image.In this paper, according to the disadvantages of ultrasound image such as low contrast, low signal-to-noise ratio. We have proposed a novel enhancement approach based on the notion of nonstationary degree of the signal or image. With the proposed approach, the nonstationary degree of observed signals or images can be well captured. The features of a signal or an image such as edges, which often exhibit greater nonstationary degrees, are significantly enhanced. The results show that the proposed approach allows improving considerably the quality of ultrasound images.Firstly, it was introduced the source of this project, the background of medical ultrasound image processing research status in domestic and overseas. Also, the significance of studying ultrasound image processing was analyzed roundly. Image enhancement and realistic meaning of this task were shown. Furthermore, it was illustrated the interrelated knowledge of medical ultrasound image, including the development of ultrasound technique, the principle of ultrasound imaging, and the format of equipments used and the collection mode of the equipments. Character of medical ultrasound image was also discussed to establish the foundation for continuous processing.Secondly, it was introduced the principle and definition of random process briefly to establish the foundation for continuous research in the following deduction. Put emphasis on introducing the notion of nonstationary degree of the signal, and deduced a novel enhancement approach based on this notion,which was called NSD algorithm, then put this algorithm to simulating signal. The result verified the accuracy and superiority of this algorithm.And at last, we have applied the NSD algorithm to the ultrasound image of carotid artery to enhance the image. Through choosing the better parameter to obtain better result, we finally get the clearer enhanced image compared to the original image. The NSD algorithm could project the edge of the tissue so that we can see the structure of carotid artery. The processing result showed a good performance of NSD algorithm. And then, we set a threshold value to realize the carotid artery edge detection.