Development of MRF for Characterization of Brain Tumors After Radiotherapy

Inclusion Criteria for Healthy Participants: * Ages 18 - 60 * No history of cerebrovascular disease * No cognitive impairments * Able to provide informed consent Inclusion Criteria for Participants with Brain Tumors: * Biopsy-proven cases of developed recurrent tumor or radiation necrosis, OR * a. PET identified with developed recurrent tumor or radiation necrosis. OR * b. Highly suspicious case with developed recurrent tumor or radiation necrosis confirmed by tumor board, attending physician or surgeon. * ECOG performance status 0-2. * Life expectancy \> 6 months. * Participant with other sites of extracranial metastatic disease or any prior or current systemic therapies will be considered and evaluated by the investigators of the study on a subject basis. Inclusion Criteria for Participants with Brain Metastases or Primary Gliomas: * Radiology identified with developed primary gliomas tumor or brain metastases, OR * a. PET identified with developed gliomas tumor or brain metastases, OR * b. Highly suspicious case with developed gliomas tumor or brain metastases confirmed by tumor board * Participants must not have received prior radiation or surgical treatment for brain metastases or primary glioma. * Age: 18 years and over * ECOG performance status 0-2 * Life expectancy \> 6 months. * Participant with other sites of extracranial metastatic disease or any prior or current systemic therapies will be considered and evaluated by the investigators of the study on a subject basis. Inclusion Criteria for Participants with Meningiomas: * Radiology identified with resectable meningioma * Participants have no prior radiation or surgical treatment for brain lesions * Age: 18 years or older * ECOG performance status 0-2 * Life expectancy \> 6 months. * Participants with other sites of extracranial metastatic disease or any prior or current systemic therapies will be considered and evaluated by the investigators of the study on a subject basis. Exclusion Criteria: * Pregnant women OR lactating women * Participants with ferromagnetic or otherwise non-MRI compatible aneurysm clips. * Participants who cannot go into the MRI scanner due to metal implants and other medical conditions. * The presence of an implanted medical device that is not MRI-compatible, including, but not limited to: pacemaker, defibrillator. * Participants with contraindications for MRI due to embedded foreign metallic objects such as bullets, shrapnel, metalwork fragments, or other metallic material. * Known history of severe claustrophobia. * Participants unable to lay still in the scanner for 30 minutes at a time.