Generalized subtraction methods in digital mammography.

Digital mammography can greatly facilitate new applications, with the potential of further improving early diagnosis of breast cancer. Indeed, early manifestations of breast cancer are often very subtle and are displayed on the variable pattern of normal anatomy that may either obscure or simulate disease. This is particularly important in dense breasts, because of the complexity of overlying fibroglandular structures. The requirement of improved lesion conspicuity has brought to the application of a number of subtraction methods such as the tomographic technique to exploit depth-dependent information or the digital angiography where subtraction in the temporal domain is applied in conjuction with administration of contrast medium. Since there are various parameters that might be used for subtraction, such techniques have to be intended in generalized form. Generalized subtraction methods in mammography are here presented and compared.