Molecular Determinants of Persistent Cancer Related Fatigue

Inclusion Criteria: All Participants: \- Women age 18 or older with no contraindication to magnetic resonance imaging(MRI); Fatigued BC Participants: * Have a diagnosis of breast cancer; * And have completed all cancer-related treatments (i.e., surgery, chemotherapy, radiotherapy, immunotherapy, etc.) except for hormonal therapy and or herceptin at least 12 weeks previously; and be apparently cancer-free. Age-Matched, Healthy Participants: * Generally healthy; * Matched in age ± 2.5 years to a Fatigued BC participant. * No prior history of any cancer except for basal cell or squamous cell tumors of the skin that have been surgically excised; * Have good sleep quality * Have no chronic pain * Have no chronic fatigue Exclusion Criteria: * Pregnant, wanting to become pregnant or lactating women ; * Diagnosed with anemia \[defined as hemoglobin levels \< 12 gm/dl\] or receiving treatment for anemia ; * Diagnosed with any comorbidities likely to cause significant fatigue (i.e., moderate to severe heart failure) * Diagnosed with nutritional deficiencies; * Have a diagnosis of untreated hypo- or hyper-thyroidism * Have an initiation, a cessation or change of dose (up to three weeks prior to the study's start) of any chronic medications or dietary supplements or any planned change of chronic medications or dietary supplements during the study; * Have implanted (e.g., surgical clips or staples) metal objects.