Both of these mechanismseventually merge in the activation of executioner caspases such ascaspase-3 and caspase-7., As a result, caspase-3and caspase-7, which share significant homology, have been hypothesizedto be potential targets by PET radiotracers to image apoptosis.−,  Caspase specific radiotracers have been designed to bind to activatedcaspases, or to be caspases-cleavable as a reporter-like mechanism.Although a variety of PET probes for caspase-3 have been reported,few have been designed to image cell death in neurodegenerative disease,due to presence of the BBB. The gene discussed is CASP7; the disease is neurodegenerative disease.