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Radioactive tracer i131 uptake

Radioactive tracer for an i-131 thyroid uptake scan

About[]

A radioactive tracer, also called a radioactive label, is a substance containing a radioisotope that is used to measure the speed of chemical processes and to track the movement of a substance through a natural system such as a cell or tissue. A number of different radioactive forms of hydrogen, carbon, phosphorus, sulfur, and iodine are commonly used in applications including biochemical assays, metabolism studies, and medical diagnostics.

Common tracer isotopes[]

A number of different radioisotopes are used as radioactive tracers depending on the application. We will talk about one commonly used isotope.

Iodine[]

Iodine-123 is a radioactive form of iodine that contains 70 neutrons and 53 protons in its nucleus. Iodine-123 decays into tellurium-123 by electron capture, producing gamma rays. Iodine-123 is used in nuclear medicine imaging, specifically to study thyroid function. Because of its short half life, Iodine-123 is the most frequently used isotope in thyroid function studies.

Iodine-125 is a radioactive form of iodine that contains 72 neutrons and 53 protons in its nucleus. Iodine-125 decays into tellurium-125 by electron capture, producing gamma rays. Iodine-125 is frequently used in radioimmunoassays because of its relatively long half life and ability to be detected with high sensitivity by gamma counters.

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