Thyroid Imaging with Iodine

Many radioactive isotopes are used in medicine for imaging and treatment purposes. The specific isotopes used depends on the particular organ or body system being studied (for example, Xe-133 is used to image lung function and blood flow.) For thyroid imaging, isotopes of iodine are used, commonly 1-123 and 1-131, which have half-lives of 13.2 hours and 8.0 days, respectively.
Why is iodine used for thyroid imaging (as opposed to any other element)? 1-129 is an extremely rare isotope of iodine with a half-life of 15.7 million years. Assuming it was much more abundant in nature, would 1-129 be a good substitute for 1-123 or I-131 in thyroid imaging? Why or why not? Although both 1-123 and 1-131 can be used in imaging of the thyroid, only I-131 is used in treating thyroid cancer. What difference in radioactivity between 1-123 and 1-131 accounts for this preference? Sometimes non-radioactive isotopes of iodine can be preferred depending on the intended medical use. For example, many people preparing for a nuclear disaster stockpile KI tablets (non-radioactive). Why would someone consume KI during a radioactive disaster? Would you consider purchasing KI tablets as a precaution? Why or why not?










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