A radioconjugate composed of choline labeled with the positron-emitting isotope fluorine F 18, with potential tumor tracer activity using positron emission tomography (PET). Fluorine F 18 fluorocholine incorporates into tumor cells through an active, carrier-mediated transport mechanism for choline and then is phosphorylated intracellularly by choline kinase, yielding a phosphoryl derivative, that is integrated into the cell membrane as part of phosphatidylcholine. Since the proliferation of cancer cells is much higher than normal cells, tumor cells exhibit an increased rate of fluorine F 18 fluorocholine uptake and incorporation, facilitating imaging of the tumor using PET. Choline kinase, the enzyme responsible for the phosphorylation of choline, is frequently upregulated in human tumor cells. Choline is essential for the production of phosphatidylcholine, which is an important element of phospholipids in cell membranes. Check for active clinical trials using this agent.