An apparatus for imaging a breast of a patient has a gantry with a radiation source and a sensor, the source and sensor rotatable in an arcuate orbit about a central axis and within a plane of revolution, wherein the arcuate orbit spans more than 180 degrees and less than 360 degrees, and wherein the gantry has a gantry cover that is disposed to be in contact with at least the chest wall of the patient. The gantry cover has a central opening about the central axis for insertion of the breast that is to be imaged and a peripheral cutout portion that defines the end-points of the arcuate orbit and that provides a space for positioning a portion of the patient's anatomy.