Inclusion Criteria:  Screening Group:  Female sex of any ethnicity Age 40 years or older Scheduled for a routine screening mammography exam within 4 weeks.  Diagnostic Group:  Female sex of any ethnicity Age 20 years or older Have an abnormality detected by Breast Self Exam (BSE), or Clinical Breast Exam (CBE), or have an abnormality detected by an imaging modality. Will undergo diagnostic mammography, prior to breast biopsy (if needed).  Exclusion Criteria:  Pregnancy Lactation  Unknown pregnancy status AND  has refused pregnancy testing and has refused to sign a pregnancy test waiver Women who are unable or unwilling to understand or to provide informed consent Women with physical limitations that may prohibit resting prone on the exam table, such as, but not limited to: frozen shoulder, recent heart surgery, pace maker. Women who are unable to tolerate study constraints.  Women who have received radiation treatments to the thorax or breast area for malignant and nonmalignant conditions, such as (but not limited to):  Treatment for enlarged thymus gland as an infant Irradiation for benign breast conditions, including breast inflammation after giving birth Treatment for Hodgkin's disease Women who have participated in a prior breast clinical trial that gave additional radiation dose, such as an additional mammogram.  Women who have received large numbers of diagnostic x-ray examinations for monitoring of disease such as (but not limited to):  Tuberculosis Severe scoliosis Additional exclusion criteria due to machine limitations Patient's body weight is over the limit of the scanner table (440 lbs. or 200kg)