This study will enroll patients with brain metastases that are evolving after SRS who are scheduled to undergo surgical resection. Eligible patients will undergo an 18F-FCH PET study 1-to-7 days pre-operatively. Although no toxicity has been previously reported following 18F-FCH administration, patients will be contacted 1-3 days after their scan and asked whether they experienced any adverse effects. The patients who have a positive 18F-FCH PET study (in which there is visible focal "hot spots" (a focus of lesion/normal white matter ratio >1.4) of 18F-FCH) will undergo further evaluation and be administered a second administration oflower activity 18F-FCH at the time of surgery. The purpose of the second 18F-FCH administration in the operating room is to further elucidate the tissue distribution of 18F-FCH radioactivity with respect to the histopathology of the surgically resected tissue.

by comparing the PET imaging results to the surgical pathology