Figure 2. Fused PET and CT image of a patient with oropharyngeal carcinoma, where ⁶⁴Cu-diacetyl-bis(N(4)-methylthiosemicarbazone) (⁶⁰Cu-ATSM) is used as the hypoxia tracer. The image illustrates regions of heterogeneous ⁶⁰Cu-ATSM intensity within the gross tumour, representing the presence of tumour hypoxia. Reproduced with kind permission from: Chao KS, Bosch WR, Mutic S, et al. A novel approach to overcome hypoxic tumor resistance: Cu-ATSM-guided intensity-modulated radiation therapy. Int J Radiat Oncol Biol Phys 2001;49:1171–82.