1. A method to perform image preprocessing for mammography CAD and workstation, comprising the steps of: detect left and right laterality of the chestwall in the mammogram; arrange the mammogram image so chestwall side align the left side; detect bright or black edges along 4-side of the image; segment breast tissue; detect separation curve line between breast tissue and pectoral muscle; perform pseudo-modality image normalization based on breast segmentation and pectoral muscle segmentation; clip edge, mask breast tissue, arrange images to chestwall-to-chestwall layout (hanging protocol).