1. A method for automatic boundary segmentation of an object in a medical image, comprising the steps of: determining a point indicating a center or an approximate center of an object in a medical image displayed on a display; applying a filter to the medical image so as to determine candidate pixels as edge pixels indicating a boundary of the object; removing linked candidate pixels, a length of the linked candidate pixels being shorter than a predetermined threshold; determining a pixel among the candidate pixels as a false edge of the boundary of the object by using domain knowledge and removing the candidate pixel determined as the false edge; identifying a candidate pixel which is first detected when the medical image is scanned along each radial direction and remaining candidate pixels; removing a candidate pixel from the remaining candidate pixels by fitting a polynomial to the remaining candidates; generating a closed contour as the boundary of the object by applying a Discrete Dynamic Contour (DDC) model to the candidate pixel which is first detected when the medical image is scanned along each radial direction and the remaining candidates other than the candidate pixel removed by fitting a polynomial to the remaining candidate; and displaying the closed contour on the display.