18FMISO will be synthesized as previously described (20). The synthesis of 18F-FAZA will be performed as follows (21):5 mg of the precursor 1-(2,3-diacetyl-5-tosyl-a-D-arabinofuranosyl)-2-nitroimidazole in 1 mL of dimethyl sulfoxide were reacted with the mixture of azeotropically dried 18F-fluoride, 15 mg of Kryptofix 2.2.2. (Merck), and 3.5 mg of K2CO3 at 100C for 5 min. After hydrolysis with 1 mL of 0.1 N NaOH (2 min,30C), 0.5 mL of 0.4N NaH2PO4 was added for neutralization. The product was purified first using an alumina cartridge (Alu N light; Waters) and then high performance liquid chromatography (HPLC) (Phenomenex Nucleosil C18; ethanol/NaH2PO4 buffer (5:95); flow, 4mL/min; detection ultraviolet (320nm), Na(Tl)). The product was obtained in radiochemical yields of 20.7%+-3.5% (n=12) at end of the beam. After irradiations of 1 h at 35µA, 9.1 +-1.4GBq (n=8) 18FFAZA will be isolated.