Evaluation of Half-Dose Molecular Breast Imaging With Wide Beam Reconstruction Processing

Inclusion Criteria: Subgroup 1, Patients with breast lesions: -At least one breast lesion detected by mammogram, ultrasound or breast MRI that measures \< 20 mm in greatest dimension, presents as a mass, is considered suspicious or highly suggestive of malignancy according to the Breast Imaging Reporting and Data System Atlas criteria (BIRADS 4 or 5), and is scheduled for core-needle biopsy or surgical biopsy. OR -At least one breast lesion that measures between \> 10 mm but \< 20 mm in greatest dimension, presents as a mass, is biopsy-proven as malignant, and is scheduled for surgical resection. AND * Age \> 40 years * Negative pregnancy test, postmenopausal, or surgically sterilized Subgroup 2, Patients without known breast lesions: * Negative screening mammogram performed at Mayo Clinic Rochester within 15 months prior to performance of study MBI * No signs or symptoms of breast disease * Age \> 40 years * Negative pregnancy test, postmenopausal, or surgically sterilized Exclusion Criteria: * Vacuum-assisted or excisional biopsy has been performed prior to the study MBI. Reason: these types of biopsies are more likely to remove all of the tumor * MBI is performed after biopsy and neo-adjuvant chemotherapy is planned prior to surgery. Reason: true tumor size will not be able to be ascertained from the final pathology findings * Breast implants. Reason: cases with breast implants will be easily identifiable on blinded interpretation to take place at the study end * Suspected that breasts will not fit in the MBI field of view. Reason: cases that require tiled views or additional views will be easily identifiable on blinded interpretation to take place at the study end * Only one breast remaining. Reason: unilateral cases will be easily identifiable on blinded interpretation to take place at the study end; injection timing is designed for bilateral views * Pregnancy test (if necessary) is not negative, or the patient is unable to complete the pregnancy test * Physically unable to sit upright and still remain still during two consecutive MBI studies over the course of a 2-hour period.