Detection of small tumors in the breast: combining tomography with digital subtraction

Digital subtraction mammography is used to detect gross radiographic changes in breast tissue, but small tumors are missed. The inability to ensure exact positioning of the breast in the mamography machine every time, due to its loose and non-rigid nature causes a large amount of misregistration noise in the difference image. Since the size of the noise is comparable to the size of the tumor being detected, tumors seldom get detected before they metastasize. We propose a new technique based on submamograms. Submamograms are projection images of slabs of the breast which are computed from standard mammograms taken from a few different angles. Subtraction images derived from corresponding submamograms show more clearly those features in the breast that have undergone a change in the interval between examinations.