= Solution
A diagnostic example is <technetium-99m methylene diphosphonate>, which accumulates at sites of bone turnover for <bone scintigraphy>. A therapeutic example is <sodium iodide iodine-131>, taken up by thyroid tissue and used for selected thyroid disease including differentiated thyroid cancer.
For diagnosis, an escaping <gamma ray> or a <Positron> followed by annihilation <photons> allows external detection, with an appropriate short <half-life> and limited deposited <energy>. For molecular <radiotherapy>, short-range charged emissions such as <beta particles>, <alpha particles> or <Auger electrons> deposit substantial local <energy> in the targeted tissue. <Iodine-131> emits therapeutic <beta particles> as well as imageable <gamma rays>, so these categories are functional rather than mutually exclusive isotope classes.
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