Novel radiopharmaceuticals for imaging unique metabolic pathways in cancer: Amino acids play an important role in many biological processes, serving a key role in protein synthesis and as substrates for important intermediary metabolic processes and cell signaling pathways. This makes them prime candidates for templates for new medical imaging probes – substances that can be used to diagnose and track the development of diseases. To this end, TRIUMF has developed novel tracers toward two molecular systems: xC- and LAT1. System xC- helps to maintain homeostasis via antioxidant/free radical management at the cellular level, while the LAT1 transporter is an important component of protein synthesis in cells. TRIUMF has developed 18F-fluoroaminosuberic acid (18FASu) as a specific positron-emitting substrate of system xC-; and via collaborative efforts with scientists at SFU, a series of leucine-like radiolabeled amino acids as substrates of LAT1. Studies are ongoing to establish the utility of both tracers in the detection, staging and treatment monitoring of a number of different cancers.