1. A method for facilitating temporal comparison of breast mammograms by a viewer, comprising: receiving a prior mammographic image originating from a first mammogram acquisition system and having a first tissue distance per pixel; receiving a subsequent mammographic image of the breast originating from a second mammogram acquisition system different than the first mammogram acquisition system and having a second tissue distance per pixel different than the first tissue distance per pixel; and without requiring a scale-adjusting viewer input, displaying for simultaneous viewing said prior and subsequent mammographic images on a same mammogram display at an identical tissue distance per unit display distance.