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?
