Iodine-124 has been produced by the irradiation of 96% enriched [124Te]tellurium (iv) oxide with 15 MeV deuterons via the 124Te(d,2n)124I nuclear reaction [30-32]. Iodine-124 has also been produced by the irradiation of enriched [124Te]tellurium (IV) oxide with 15 MeV protons via the 124Te(p,n)124I nuclear reaction . Some work has been performed utilizing lower energy 11 MeV proton cyclotrons to produce [124I]iodide [29,34,35], but the yields have been relatively low. While 124I has a relatively long half-life (4.2 days), there are problems associated with its use. Like 76Br, 124I has a complex decay scheme with only about 25% of its transitions resulting in positron emission, and the emitted positron has a relatively high energy compared to positrons from 18F (Table 9.1). In addition, several high-energy gamma rays of nuclear origin are emitted along with the positron. Despite these complications, 124I has been used successfully to label PET radiopharmaceuticals because its long half-life provides advantages over 18F for imaging slow pharmaco-kinetic processes in vivo. In addition, it is possible to achieve relatively high-specific-activity products using electrophilic radiolabeling methods with 124I.
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