Serial MRI Scans During Radiation Therapy

This is a phase 1 study to determine the feasibility and utility of using serial magnetic resonance imaging (MRI) to assess treatment response during and after radiation therapy (standard of care cancer treatment) for participants with advanced esophageal cancer, glioblastoma, prostate cancer, vulvar cancer or pediatric glioma. The research study procedures include three MRI scans (one before, one during, and one after standard of care cancer radiation therapy) for participants with advanced esophageal cancer, glioblastoma, prostate cancer, vulvar cancer or pediatric glioma. The research study procedures include: * Screening for eligibility * Three MRI scans