a diagnostic computed tomographic imaging apparatus , comprises a patient support structure including a tabletop to support a patient in front - down , prone position . the tabletop includes an opening to permit a breast of the patient to be vertically pendant below the tabletop . a scanning mechanism is disposed below the opening and orbitable about the breast pendent through the opening to obtain perimeter data and image reconstruction data of the breast . the scanning mechanism rotates about an axis of rotation transverse to the tabletop . one of the tabletop and scanning mechanism is movable in x - y axes to center the breast about the axis of rotation .