Radiotracer A radioactive nuclide, introduced

Radiotracer a radioactive nuclide, introduced into an organism for diagnostic purposes, whose pathway can be traced by monitoring its radioactivity. (21.4)... 

Radiotracer a radioactive nuclide introduced into an organism and traced for diagnostic purposes. 

The use of radioactivity in diagnosis usually involves a radiotracer, a radioactive nuclide attached to a compound or introduced into a mixture in order to track the movanent of the compound or mixture within the body. Tracers are useful in the diagnosis of disease because of two main factors (1) the sensitivity with which radioactivity can be detected, and (2) the identical chemical behavior of a radioactive nucleus and its nonradioactive counterpart. For example, the thyroid gland naturally concentrates iodine. When a patient is given small amounts of iodine-131 (a radioactive isotope of iodine), the radioactive iodine accumulates in the thyroid, just as nonradioactive iodine does. However, the radioactive iodine emits radiation, which can then be detected with great sensitivity and used to measure the rate of iodine uptake by the thyroid, and thus to image the gland. 

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