The purpose of this study is to discover the potential convenience and ease of using a Magnetic Resonance Imaging (MRI) technique, named Magnetic Resonance Fingerprinting (or MRF), to achieve high-quality images within a short scan time of 5 min for viewing the entire brain. This is an advanced quantitative assessment of brain tissues. This method is being applied with IVIM MRI to be able to tell the difference between a brain with radiation necrosis and a brain with tumor recurrence. Participants will consist of individuals who have received radiation therapy in the past and were diagnosed with radiation necrosis, individuals with recurrent tumors, individuals with previously untreated tumors, and healthy individuals who have no brain diseases and have not had radiation treatment to the brain. Participants will undergo an MRI scan at a one-time research study visit; no extra tests or procedures will be required for this research study.

The primary objectives of this study are:

• To demonstrate the clinical feasibility of combining MRF with state-of-the-art parallel imaging techniques to achieve high-resolution quantitative imaging within a reasonable scan time of 5 min for whole brain coverage.
• To apply the developed quantitative approach in combination with IVIM MRI for differentiation of tumor recurrence and radiation necrosis.
• To investigate the effect of radiation dose on the development of radiation necrosis and tumor recurrence.

Although Stereotactic radiosurgery (SRS) is utilized as an effective treatment method, after several months to over 1 year following SRS, 33% of treated brain metastases increase in size on imaging, which is suspicious for tumor progression. However, based on findings in follow-up biopsies, the majority of newly detected metastases on imaging are radiation treatment effects instead of active tumor. So far, the only gold standard to differentiate active tumor and radiation necrosis is surgical resection for pathologic confirmation, which is invasive, not favored for poor surgical candidates, and should be avoided in cases of necrosis. The existing clinical imaging techniques have poor sensitivity or specificity in differentiating these two types of tissues. Recently, a novel MRI data acquisition approach, namely MR Fingerprinting (MRF), has been introduced for the simultaneous measurement of multiple important parameters in a single MRI scan. In addition, quantitative diffusion MRI, such as the intravoxel incoherent motion (IVIM) technique, can provide a noninvasive and powerful tool to quantify microstructural information by measuring water diffusion and microcirculation perfusion in vivo. This study aims to demonstrate the clinical feasibility of combining MRF with state-of-the-art parallel imaging techniques to achieve high-resolution quantitative imaging within a reasonable scan time of 5 min for whole brain coverage. It also aims to apply the developed quantitative approach in combination with IVIM MRI for the differentiation of tumor recurrence and radiation necrosis. The multi-parametric quantitative measures developed in this study could establish a new fundamental biomarker for the diagnosis and monitoring of brain tumors.

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.