Isotopes of iodine iodine-123 and iodine-131 can also be seen by single photon emission computed tomography (SPECT) imaging. Iodine-124 is a proton-rich isotope of iodine with a half-life of 4.18 days. Its modes of decay are: 74.4% electron capture, 25.6% positron emission. I decays to Te. Iodine-124 can be made by numereous nuclear reactions via a cyclotron. The most common starting material used is Te. Iodine-124 as the iodide salt can be used to directly image the thyroid using positron emission tomography (PET). Iodine-124 can also be used as a PET radiotracer with a usefully longer half-life compared with fluorine-18 In this use,
Iodine the iodyl cation, [IO], and is reduced by concentrated sulfuric acids to iodosyl salts involving [IO]. It may be fluorinated by fluorine, bromine trifluoride, sulfur tetrafluoride, or chloryl fluoride, resulting iodine pentafluoride, which also reacts with iodine pentoxide, giving iodine(V) oxyfluoride, IOF. A few other less stable oxides are known, notably IO and IO; their structures have not been determined, but reasonable guesses are I(IO) and [IO][IO] respectively. More important are the four oxoacids: hypoiodous acid (HIO), iodous acid (HIO), iodic acid (HIO), and periodic acid (HIO or HIO). When iodine dissolves in aqueous solution, the following reactions occur: Hypoiodous