Inclusion Criteria:  • Female  40 to 69 years Previous normal mammogram (BI-RADS 1 or 2) showing heterogeneous or extremely dense breast tissue within last 24 months Scheduled for screening mammogram as part of the patient's clinical care  Exclusion Criteria:  • No mammogram within last 24 months  Fatty or scattered fibroglandular tissue on last mammogram History of allergy to iodinated contrast History of renal disease or renal function abnormalities Pregnant women History of diabetes History of paraproteinemia syndromes such as multiple myeloma History of collagen vascular disease History of vascular disease (coronary artery disease, myocardial infarction, carotid disease, peripheral vascular disease, or known visceral artery disease) Previously identified as high risk for breast cancer (>20% lifetime risk) Asthma Sickle Cell Anemia Currently on Dialysis