**2.3 Radiolabeled caspase targeted tracer**

Caspase activation is the central role in the execution of cell death, therefore, caspases are the attractive targets for apoptosis imaging. Non-peptide based isatin sulfonamide analogs were synthesized with nanomolar potency for inhibiting caspase-3 and caspase-7 and one of the analogs, WC-II-89 was labeled with 18F (Zhou et al., 2006). 18F- WC-II-89 showed a high uptake in the liver of chemically induced apoptosis. Although molecules that target caspase-3 is attractive, there are limited animal data and it is not yet known how sensitive this kind of agents will be for actual imaging in humans.
