The goal of this diagnostic intervention clinical trial is to compare 18F-Fluciclovine uptake within brain lesions over 60 minutes compared with standard of care positive histology confirmation or confirmation MRI images. The main questions it aims to answer are: 1. What are the dynamics of 18F-Fluciclovine update within a non-treated metastatic brain lesion over 60 minutes? 2. What are the dynamics of 18F-fluciclovine update within recently treated metastatic brain lesions? 3. What is the potential use of 18F-Fluciclovine in delineating true local progression from radionecrosis in patients with clinical uncertainty of indeterminate MRI? Participants will undergo an 18F-fluciclovine head PET/CT scan prior to treatment for brain metastatic lesion(s). The study will characterize uptake dynamic PET images over 60 minutes. Uptake within the lesions and the benign brain parenchyma will be plotted on a time activity curve for 60 mins. Patients will undergo a second 18F-fluciclovine PET/CT to evaluate 18F-fluciclovine uptake in treated lesions over 60 minutes. This will be offered concurrently with the post-procedure standard of care (SOC) MRI to evaluate post-treatment changes. Uptake within the lesions and the benign brain parenchyma will be plotted on a 60 min time activity curve. Results will be compared to the pre-treatment baseline images. A third 18F-fluciclovine PET/CT will be offered to evaluate post radiation changes necrosis from recurrence, for up to 10 patients in our cohort who are under clinical surveillance (up to three years surveillance) and developed MRI evidence of either true progression or radionecrosis with clinical uncertainty after stereotactic radiosurgery. The initial 18F-fluciclovine PET/CT will serve as a baseline PET/CT scan. This will be compared to post procedural histological confirmation.