An Adaptive Line Boundary Detection Technique in Medical Ultrasonic Image
GUO Sheng-wen, LUO Li-min (Department of Biomedical Engineering,Southeast University, Nanjing 210096)
There is a kind of noise called speckle in ultrasonic images. It degrades severely the quality of image, especially edges and details. An adaptive line boundary detection technique is presented. A stick is a line segment of variable length and different orientation. Sticks are short enough that they can locally approximate the edges and certain features in the image. In particular, tissue boundaries have the appearance of straight or gently curving line segments because they are cross-sectional views of the surfaces between tissue layers. The boundaries and certain details are smooth on the scale of spacing between scan lines and generally define closed convex shapes. The algorithm works by plotting at every point the maximum local projection onto the stick. The orientation of stick is decided by hypothesis test optimizing method and the length of stick is obtained by local statistics based on region growing technique. For quantitative evaluation and comparison with adaptive speckle suppression filter (ASSF) and line edge detector(LED), two parameters as measure of the noise suppression and edge preservation are introduced. It is proved that this method can not only suppress speckle noise but also preserve even enhance issue boundary effectively by applying it to the phantom and tissue images.