In parallel to ER-targeted PET imaging in breast cancer with 16α-18F-fluoro-17β-estradiol ([18F]FES), androgen receptor (AR)-targeted PET imaging in prostate cancer is possible using 18F-fluorodihydrotestosterone (18F-FDHT; Figure 3), which binds the intracellular AR in prostate cancer cells (93). The gene discussed is AR; the disease is breast carcinoma.