forms the largest connected component above this threshold the thresholding process is followed by a process in which the largest connected component in the binary image is selected up sampled and dilated using a circular structure element of radius 15 pixels advantageously this technique provides a reasonable template of the breast having selected the region of interest local minima in the intensity surface of the region of interest are identified using a feature extraction process 14 here all single pixel local minima in the region of interest are identified by comparing each pixel 39 s intensity values to a minimum intensity value determined for its eight adjacent pixels having identified the single pixel local minima in the region at step 16 a pixel neighbourhood is identified for each pixel having a local minimum intensity value in the preferred embodiment of the invention step 16 involves a first processing step 16 1 and a second processing step 16 2 for each local minimum in the first processing step 16 1 intensity values for plural pixel sets associated with a local minimum are processed here each pixel set has one of several non overlapping paths the paths are substantially concentric about the local minimum and substantially equally spaced in.