FES BPET-DBT in Newly Diagnosed Breast Cancer

Inclusion Criteria: 1. Participants will be ≥ 18 years of age. 2. Known ER positive (by immunohistochemistry) breast cancer. 3. At least one lesion ≥ 1.0 cm that is seen on standard imaging (e.g. mammogram, ultrasound, MRI, CT, FDG-PET/CT). Only one type of imaging is required to show a lesion. 4. Participants must be informed of the investigational nature of this study and be willing to provide written informed consent and participate in this study in accordance with institutional and federal guidelines prior to study-specific procedures. Exclusion Criteria: 1. Females who are pregnant or breast feeding will not be eligible for this study; a urine pregnancy test will be performed in women of child-bearing potential prior to PET imaging.. 2. Inability to tolerate imaging procedures in the opinion of an investigator or treating physician. 3. Currently taking tamoxifen or raloxifene 4. Any current medical condition, illness, or disorder as assessed by medical record review and/or self-reported that is considered by a physician investigator to be a condition that could compromise participant safety or successful participation in the study.