Patent ID: 6035056
Filing Date: 2000-03-07
Classification: G06K,G06T

Abstract:
A method of identifying a pectoral boundary in a digital mammogram, said pectoral boundary being characterized by at least one parameter, comprising the steps of:determining a region of interest containing said pectoral boundary;calculating gradient magnitudes inside said region of interest;accumulating said gradient magnitudes into a parameter plane, represented by H(.rho.,.theta.), according to a Hough transform; andusing information in said parameter plane for identifying said at least one parameter of said pectoral boundary;wherein said step of using information in said parameter plane comprises the steps of:selecting a parameter plane region of interest corresponding to the range of possible angles normal to said pectoral boundary;creating a normalized parameter plane HN(.rho.,.theta.) by normalizing the value H(.rho.,.theta.) by a normalizing factor, said normalizing factor being inversely related to the number of gradient magnitude pixels capable of being accumulated at (.rho.,.theta.);identifying a highest ranking local peak of said normalized parameter plane HN(.rho.,.theta.); andusing the location of said highest ranking local peak for determining said at least one parameter of said pectoral boundary; andwherein said normalizing factor is determined for each pixel (.rho.,.theta.) by the steps of:backprojecting a line corresponding to (.rho.,.theta.) into the image plane;determining the length L of said line; andsetting said normalizing factor equal to 1/sqrt(L) if L is greater than a first number of pixels.