To further validate radioluminescence microscopy, we investigated the uptake of 9-(4-[18F]Fluoro-3-hydroxymethylbutyl)guanine (FHBG) in cancer cells that were heterogeneously transfected to express the mutant herpes simplex virus type 1 truncated thymidine kinase (HSV1-ttk). The gene discussed is TTK; the disease is cancer.