RecruitingDrug trialComparative Performance of Molecular Breast Imaging (MBI) to Magnetic Resonance Imaging (MRI) of the Breast in Identifying and Excluding Breast Carcinoma in Women at High Risk for Breast CancerTo evaluate the diagnostic performance of Tc99m sestamibi (MBI) compared to breast MRI in women who are at high risk for developing breast cancer. To assess the relationship of tumor size, histologic subtype and location of lesion and how it affects lesion conspicuity and sensitivity in MBI detected cancers.