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,
Tincture of iodine drinking. When an alcohol solution is not desirable for this purpose, the alcohol-free Lugol's iodine, an aqueous solution of iodine in potassium iodide solution, or else povidone-iodine (brand names Wokadine, Betadine), a PVPI solution, can be used. Small amounts may be added to suspect drinking water as a disinfectant (typically 5 mg free iodine per liter, or 5 drops of 2% tincture). Though this treatment is effective against bacteria and virus, it does not protect against protozoan parasites such as "Cryptosporidium" and "Giardia". Iodine solution is used to sanitize the surface of fruit and vegetables for bacteria and virus. The