This early phase I trial tests the use of a radioactive tracer (a drug that is visible during an imaging test) known as 18F-FMAU, for imaging with positron emission tomography/computed tomography (PET/CT) in patients with brain cancer or cancer that has spread to the brain (brain metastases). A PET/CT scan is an imaging test that uses a small amount of radioactive tracer (given through the vein) to take detailed pictures of areas inside the body where the tracer is taken up. 18F-FMAU may also help find the cancer and how far the disease has spread. Magnetic resonance imaging (MRI) is a type of imaging test used to diagnose brain tumors. 18F-FMAU PET/CT in addition to MRI may make the finding and diagnosing of brain tumor easier.

PRIMARY OBJECTIVES:

I. Assess the correlation between multiparametric magnetic resonance imaging (mpMRI) radiomics and dynamic 2'-fluoro-5-methyl-1-beta-D-arabinofuranosyluracil (FMAU) PET kinetic analysis parameters.

II. Explore the different pattern in radiomics mpMRI and FMAU PET kinetic analysis parameters between patients with presence or absence of recurrent tumor.

OUTLINE:

Patients receive 18F-FMAU intravenously (IV) and undergo a PET/CT scan over 60 minutes. Patients then undergo standard of care mpMRI over approximately 45 minutes.

After completion of study intervention, patients are followed up at 24-96 hours after their 18F-FMAU PET/CT scan.

Inclusion Criteria:

• Age > 18 years, both men and women
• Documented history of either primary brain tumor (e.g. glioma) or metastatic brain tumor from another primary cancer (e.g. lung, breast, colon, melanoma, kidney)
• Documented radiation therapy regardless of treatments prior to radiation therapy

Exclusion Criteria:

• Unable to give consent
• Inability to remain motionless during imaging studies
• Intractable seizures
• Claustrophobia
• Implantable devices incompatible with magnetic resonance (MR) environment