We have developed and validated an isatin-based caspase-3/7-specific radiotracer, 18F-ICMT-11, for the in vivo assessment of tumour apoptosis and for monitoring response to cancer therapy by PET imaging, and have also shown favourable clinical dosimetry and safety profiles of 18F-ICMT-11 in a phase I trial [14–19]. Here, CASP3 is linked to cancer.