This invention relates to a scanning apparatus for imaging the breast that employs both X-ray and ultrasound technologies to enhance the diagnosis of cancer. There is provided a method for acquiring and co-registering the X-ray and ultrasound images in three-dimensional space, so that: the breast is in the same orientation and degree of compression when X-ray and ultrasound images are obtained both sets of images are acquired simultaneously so as to minimize the time the womans breast is held stationary automated breast ultrasound images of the whole breast are acquired in a single scan both image modalities are acquired in three dimensions and radiation dose exposure to the woman is minimized. The method incorporates, in a single device, a system for acquiring full-field digital mammography and automated breast ultrasound images, and an algorithm for performing digital tomosynthesis reconstruction using these images.