• 1\. Women must have mammographically dense breasts, ACR BI-RADS® lexicon categories c or d (heterogeneous or extreme fibroglandular tissue) on their most recent prior screening.

• 2\. Women agree to not undergo whole breast screening ultrasound for the duration of the trial until the year 2 standard of care imaging.

• 3\. Women must not have symptoms or signs of benign or malignant breast disease (e.g., bloody, or clear nipple discharge, breast lump, focal breast pain).

• 4\. Women must be able to undergo intravenous (IV) administration of iodinated contrast (e.g., no contraindication to intravenous contrast administration for Omnipaque \[iohexol\], and no known allergy-like reaction to iodine or moderate or severe allergic reactions to one or more allergens as defined by the American College of Radiology \[ACR\]: https://www.acr.org/-/media/ACR/files/clinical-resources/contrast\_media.pdf).

• 5\. Women must not be pregnant or breast-feeding. All females of childbearing potential who are uncertain if they could be pregnant or may be pregnant or as per local site standard of practice in women undergoing DBT and CESM must have a negative blood test or urine pregnancy test prior to Omnipaque (iohexol) administration. A female of childbearing potential is any woman, regardless of sexual orientation, sexual identity or whether they have undergone tubal ligation, who meets the following criteria: 1) has not undergone a hysterectomy or bilateral oophorectomy; or 2) has not been naturally postmenopausal for at least 24 consecutive months (i.e., has had menses at any time in the preceding 24 consecutive months).

• 6\. Women of childbearing potential must be strongly advised to use an accepted and effective method of contraception or to abstain from sexual intercourse for the following year until the Year 1 DBT and CESM studies are performed.