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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.

Radioiodide used in selected thyroid treatments because iodine uptake localizes activity in thyroid tissue. Iodine-131 supplies local beta radiation and imageable gamma emission.