Malignant glioma is the most common primary brain tumor in adults. Despite aggressive therapy, less than 40% of these patients are expected to live beyond 5 years. The radiologic imaging of these tumors relies on computed tomography (CT) and magnetic resonance imaging (MRI) - these studies provide good anatomical information about the size and location of the tumor, but are unable to evaluate whether the tumor is still viable or contains metabolic activity, after surgery and, in particular, radiotherapy (RT). This complicates accurate understanding of the status of the tumor during a patient's follow-up. This study proposes to add magnetic resonance spectroscopy, a non-invasive imaging method which can monitor metabolic changes in the tumor, to regular imaging. Understanding the changes that occur in a tumor over the course of radiotherapy could help predict how well a treatment might work, and could also be useful in distinguishing a return of the tumor in an area of radiation damage before it would be obvious on regular imaging.