1. A method of operating an x-ray breast tomosynthesis system comprising: acquiring a multiplicity of x-ray tomosynthesis projection images of a patient's breast at respective projection angles of an imaging x-ray beam relative to the breast; computer-processing the multiplicity of x-ray tomosynthesis projection images into a plurality of tomosynthesis slice images of the patient's breast, each tomosynthesis slice image representing a three-dimensional slab of breast tissue extending along a plane that is at respective angle relative to the breast; generating, by a computer-implemented map generator, correction information that relates differences between image information from measured values and image information from expected values for at least one of the multiplicity of x-ray tomosynthesis projection images and the plurality of tomosynthesis slice images; said correction information having been derived from multiple x-ray projection images of a phantom taken at respective different angles of an imaging x-ray beam to the phantom where said expected values relate to known information about the phantom; applying, by a computer process, said correction information to at least one of the multiplicity of x-ray tomosynthesis projection images and the plurality of tomosynthesis slice images to obtain display images of the patient's breast; and displaying the display images of the patient's breast on a display device.