As one example, the [18F]fluoromethyl-substituted celecoxib derivative was synthesized by Uddin et al.21 and evaluated in an inflammation model as well as in tumor xenografts of COX-2-negative human colorectal carcinoma (HCT116) and COX-2-expressing human head and neck squamous cell carcinoma (1483 HNSCC) providing evidence for COX-2-specific uptake of this radiotracer in vivo. Here, PTGS2 is linked to colorectal carcinoma.