The study population consists of patients who undergo resection for somatostatin receptor-positive (SSTR-positive) CNS tumors, focusing on meningioma, and including esthesioneuroblastoma, hemangioblastoma, medulloblastoma, paraganglioma, pituitary adenoma, and SSTR-positive systemic cancers metastatic to the brain, such as small cell carcinoma of the lung. The study indication is to determine the diagnostic utility of 68Ga-DOTATATE PET/MRI in the diagnosis and management of patients with SSTR-positive CNS tumors, specifically whether 68Ga-DOTATATE PET/MRI demonstrates utility distinguishing between tumor recurrence and post-treatment change. To date, the utility of Ga-68-DOTATATE PET/MRI in meningioma has not been explored. Investigators have over the past 3 months been able to accrue the largest case series of presently 12 patients in whom Ga-68-DOTATATE PET/MRI demonstrated utility in the assessment of meningioma, including assessment for postsurgical/postradiation recurrence, detection of additional lesions not visualized on MRI alone, and evaluation of osseous invasion. Based on this initial experience, investigators intend to study the impact of Ga-68-DOTATATE PET/MRI in the assessment of the extent of residual tumor in patients status post meningioma resection, specifically in patients in whom tumor location limits resectability, patients with World Health Organization (WHO) grade II/III disease, and patients with history of stereotactic radiosurgery (SRS) who develop postradiation change.

Prior to the onset of this study, the utility of Ga-68-DOTATATE PET/MRI in meningioma had not been explored. The investigator's pilot study serving as the basis for the proposed protocol resulted in the - to the investigators' knowledge - largest case series of 21 patients in whom Ga-68 DOTATATE PET/MRI demonstrated utility in the assessment of meningioma, including assessment for postsurgical/postradiation recurrence, detection of additional lesions not visualized on MRI alone, and evaluation of osseous invasion. Based on this initial experience, investigators continued to study the impact of Ga-68-DOTATATE PET/MRI in the assessment of the extent of residual tumor in patients status post meningioma resection, specifically in patients in whom tumor location limits resectability, patients with WHO grade II/III disease, and patients with history of SRS who develop postradiation change.

Inclusion Criteria:

• ≥ 18 years of age
• Diagnosis of meningioma based on pathology reports and suspected recurrence or residual disease based on standard-of-care MRI
• Additionally, patients with other somatostatin receptor 2 positive brain tumors, including esthesioneuroblastoma, hemangioblastoma, medulloblastoma, paraganglioma, pituitary adenoma, and SSTR-positive systemic cancers metastatic to the brain will be considered for the purposes of obtaining feasibility data
• As the investigator's institution, PET/MRI scanner utilizes a 3 Tesla (T) magnet, patients who may be ineligible to undergo 3T MRI but may undergo 1.5 Tesla (T) MRI, will undergo a 1.5T MRI as per clinical standard-of-care and a Ga68-DOTATATE PET/CT with the PET portion to be fused with the 1.5T MRI utilizing fusion software.

Exclusion Criteria:

• Contraindications to gadolinium-based contrast agent
• History of allergic reaction to Gallium-68-DOTATATE
• Pregnancy