1. An image viewing device for use with a mammography film displaying an image, said image viewing device comprising: (a.) a substantially flat and transparent sheet having a front surface; (b.) a scaled coordinate system visibly marked on said front surface of said sheet; (c.) a reference centerline visibly marked on said front surface of said sheet; and, (d.) a plurality of sensor position markings, wherein the number and placement of said sensor position markings is specific for a mammography imaging system.