The Mammo CESM Phantom independently verifies different beam qualities across a range of iodine concentrations and breast glandularity with tissue-mimicking materials that are an exquisite match to breast tissues. The Breast Iodine Contrast block includes breast equivalent material with 50% glandularity, divided into 11 steps with iodine concentrations ranging from 0-10 mg/cm2 along its major axis. The Adipose-Glandular blocks feature five glandularity steps (0%, 25%, 50%, 75%, 100%) along a direction orthogonal to the iodine steps of the Breast Iodine block.