Skull Base and Low Grade Glioma Neurocognitive Magnetic Resonance Imaging (MRI) Study

Inclusion Criteria: For Cohort 1 (Patients with tumor involving the base of skull) * Study subjects capable of providing informed consent. * Study subjects with an ECOG performance status of 0-1. * Study subjects aged 18 or greater. * Study subjects with a histological diagnosis of a malignancy of the paranasal sinuses or the nasopharynx requiring either definitive or post-operative radiation to a minimum prescribed dose of 60 Gy. * Study subjects deemed capable of undergoing standard CT simulation and radiotherapy treatment planning and delivery including the capacity to comply with standard immobilization devices to the head and nexk for daily irradiation. * Study subjects without any evidence of distant metastasis. * Study subjects with an estimated life expectancy of at least 1 year. * Study subjects who are able to receive a standard MRI study and deemed capable of complying with the immobilization needs. * Female study subjects of reproductive potential with a negative pregnancy test prior to each scheduled MRI study. Inclusion Criteria: For Cohort 2 (Patients with Low Grade Gliomas) * Histological confirmed diagnosis of low grade glioma of the CNS * WHO grade II * Patients must have a Karnofsky Performance Status of greater than or equal to 60. * Age greater than or equal to 18. * Patients must be able to provide informed consent. * Adequate bone marrow function:WBC greater than or equal to 4000/mm3, platelets greater than or equal to 100,000 mm3. * Women of child-bearing potential as long as she agrees to use a recognized method of birth control (e.g. oral contraceptive, IUD, condoms, or other barrier methods, etc.). Hysterectomy or meopause must be clinically documented. * Study subjects deemed capable of undergoing standard CT simulation and radiotherapy treatment planning and delivery including the capacity to comply with standard immobilization devices to the brain for daily irradiation. Exclusion Criteria: for Both Cohorts * Study subjects with questionable performance status and in whom the treating physician is suspicious that a life expectancy of at least 1 year is possible. * Study subjects with anxiety that precludes the safe administration of a MRI for the imaging time required. * Study subjects with major psychiatric diagnosis prior to neuro-oncologic diagnosis. * For neuropsychological studies, study subjects with neurological or behavioral issues that would preclude compliance with study procedures. (Karnofsky Performance Scale score of less than 60, indicating that the patients needs considerable assistance for self care and frequent medical care). * Study subjects with an inability to undergo MR Imaging for any reason. * Study subjects with a history of renal transplant or known renal disorder with a calculated GFR \> 45mL/1min \[gadolinium restriction\] * For neuropsychological studies, study subjects with mixed language background with only one year of educationin an English-speaking school. * Pregnant women, women planning to become pregnant and women who are nursing. Additional Exclusion Criteria for Cohort 2 (Patients with Low Grade Gliomas) * Prior or simultaneous malignancies within the past two years (other than cutaneous squamos or basal cell carcinoma, melanoma in situ or well differentiated thyroid carcinoma). * Patients with the following histologies are excluded: Gliomatosis cerebri, WHO III or IV gliomas.