This phase IV trial studies how well delaying positron emission tomography (PET)/magnetic resonance imaging (MRI) scan after injection of fluorodeoxyglucose (FDG) can improve the imaging of patients with cancer that has spread to brain (brain metastases). FDG is a type of imaging agent that doctors use to help "see" the images on a scan more clearly. Delaying PET/MRI scan after injecting FDG may improve how well doctors can tell the difference between healthy and unhealthy tissue.

PRIMARY OBJECTIVE:

I. To assess the optimal fludeoxyglucose F-18 (fluorodeoxyglucose) positron emission tomography (FDG PET) imaging time post radiotracer administration that maximizes separation of activity between lesion and non-lesional parenchyma (measured as lesion/background [L/B] ratio) in patients with brain metastasis.

SECONDARY OBJECTIVE:

I. To identify genotypic factors in FDG tumor metabolism derived from metrics, including maximum standard uptake value (SUVmax), mean standard uptake value (SUVmean), total lesion glycolysis (TLG), mean tumor volume (MTV), and L/B ratio.

EXPLORATORY OBJECTIVES:

I. To identify patterns of metabolism derived from metrics, such as SUVmax, SUVmean, TLG, MTV, and L/B ratio, and magnetic resonance imaging metrics, such as regional perfusion abnormalities, apparent diffusion coefficient values, fractional diffusivity measures, and magnetic resonance spectroscopic finding.

II. To identify if post treatment changes in lesion metabolism from baseline correlate with treatment success.

OUTLINE:

Patients receive fludeoxyglucose F-18 intravenously (IV) over approximately 1 minute and undergo a PET/MRI scan over 70 minutes. Within 5 hours of receiving fludeoxyglucose F-18, patients undergo a repeat PET/MRI scan over 30 minutes. Scans take place within 2 weeks before scheduled surgery and within 4-6 weeks after radiation treatment.

Inclusion Criteria:

• Pre-treatment adult patients with any solid organ metastasis and at least three intraaxial brain metastases including at least one enhancing > 10 mm lesion
• Rim or solid enhancing lesion(s) WITH a history of non-central nervous system (CNS) pathologic proven metastatic disease will be considered as a consensus between the referring radiation oncologist or neurosurgeon and a neuroradiology
• Planned surgery or radiation to the metastases
• Ability to undergo PET magnetic resonance (MR) examination

Exclusion Criteria:

• Known allergy to FDG or gadolinium based contrast agents
• History of impaired renal function (glomerular filtration rate [GFR] < 30)
• Pregnant women are excluded