<p> Researchers at Stanford have discovered a way to use labeled chlorotoxin to non-invasively assist in early cancer detection. Chlorotoxin (Cltx) was labeled with 18F via direct attachment using a chemical compound or indirect attachment using a chelator. 18F-fluorobenzoate conjugated chlorotoxin (18F-FB-Cltx) was prepared. Biodistribution and micro PET imaging of 18F-FB-Cltx in the mice bearing matrix metalloproteinase (MMP-2) positive tumors were performed. The results clearly show that 18F-FB-Cltx accumulates in the tumors in vivo. In addition, this process can also be used to image, monitor and diagnose MMP-2 positive diseases, such as, myocardial infarction, rheumatoid arthritis and atherosclerosis.