Low-dose Molecular Breast Imaging: Comparison of Breast Cancer Detection Rate at Initial Screening and Two-year Follow-up

Inclusion Criteria: \- Past prior screening mammogram within the previous 11-24 months interpreted as heterogeneously dense or extremely dense and negative or benign \[Breast Imaging Reporting and Data System (BI-RADS) Category 1 or 2\] Exclusion Criteria: Subjects will be excluded if they: * Are unable to understand and sign the consent form * Are pregnant or lactating * Are physically unable to sit upright and still for 40 minutes * Have self-reported signs or symptoms that may suggest breast cancer (palpable mass, bloody nipple discharge, axillary mass, etc.) * Have had needle biopsy within 3 months, or breast surgery or radiation within 1 year prior to the study * Are currently receiving chemotherapy or tamoxifen, raloxifene, or an aromatase inhibitor for adjuvant therapy or chemoprevention * Have undergone bilateral mastectomy * Have had a prior MBI within 20 months of scheduled study MBI.