RecruitingDevice studyTreatment Response Assessment Maps to Delineate Necrosis From Tumor After Stereotactic Radiation in Brain MetastasesThis research study is investigating the value of an imaging study of the brain called an MRI (which stands for magnetic resonance imaging), utilized in unique way, to delineate whether the tumor has recurred or whether radiation changes have occurred after a brain metastasis treated with focused radiation has enlarged.