 Upwards of 40 of cancer patients will develop brain metastases during their illness, most of which become symptomatic. The burden of brain metastases impacts the quality and length of survival. Thus the management of brain metastases is a significant health care problem. Standard treatment options include stereotactic radiosurgery andor whole brain radiation. There is a great interest in studying the association between the functional characteristics of tumors - such as tumour hypoxia and lactate accumulation - and clinical outcomes in order to guide management. These characteristics may predict future tumor behavior and stratify risk of therapy failure. Hyperpolarized 13C MR imaging is a novel functional imaging technique that uses 13C-labeled molecules, such as pyruvate, and MRS to image in vivo tissue metabolism. 