Radioactive tracer

(nucleonics) A radioactive isotope which, when attached to a chemically similar substance or injected into a biological or physical system, can be traced by radiation detection devices, permitting determination of the distribution or location of the substance to which it is attached. Also known as radiotracer.

A radioactive isotope which, when injected into a chemically similar substance or artificially attached to a biological or physical system, can be traced by radiation detection devices. Many problems in biology and medicine not amenable to other approaches can be solved by the use of these tracers. See also Radioactivity; Radioactivity and radiation applications; Radioisotope; Radioisotope (biology).

The simplest radioactive tracer studies consist of the tagging of a biological entity with a radioactive isotope (radioisotope). The entity is then tracked by following the radiation from the isotope. The operation becomes more complex when a large number of biological particles are labeled, for example, in the tagging of red blood cells or bacteria. When the labeled substance is injected into an animal, it is impossible to follow the individual labeled particles, but their average movement can be tracked by observations of the radiation. Finally, a radioisotope of a particular element can be used to tag that element. Phosphorus-32 can be introduced into the soil where a plant is growing, and the amount of phosphorus absorbed and its distribution throughout the plant can be studied.

In most biological tracer experiments, the radio-isotope is introduced into the system and its radiation subsequently measured with Geiger-Müller counters or scintillation detectors. Extremely soft (low-intensity) radiations can be detected by the use of photographic film. See also Geiger-Müller counter; Scintillation counter.

In medical applications, a radioactive atom can be attached to a molecule or more complex substance, which can then be used to examine a chemical reaction in a test tube, or it can be administered to a patient by ingestion or injection and subsequently be incorporated into a biochemical process. The radioactive emissions from the radioactive atom can be used to track (trace) the behavior of the labeled molecule or substance in biological processes by means of medical imaging, utilizing techniques such as positron emission tomography (PET) or single-photon-emission computed tomography (SPECT). See also Medical imaging.

The branch of medicine that uses radioactive tracers in the care of patients is called nuclear medicine. Radiotracers of practically every element can be produced in nuclear reactors or cyclotrons. Radioactive tracers are used as part of the diagnostic process. Three radionuclides—carbon-14, tritium (hydrogen-3), and phosphorus-32—remain the backbone of modern biomedical sciences. See also Nuclear medicine.

A molecule to which a radioactive atom has been attached so that it can be followed through a physiologic system with radiation detectors.

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A radioactive tracer, also called a radioactive label, is a substance containing a radioisotope (which is an isotope that has an unstable nucleus and that stabilizes itself by spontaneously emitting energy and particles). Tracers can be 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 a tissue.^[1] Radioactive tracing was developed by George de Hevesy.

Radioactive tracers are substances that contain a radioactive atom to allow easier detection and measurement. (Radioactivity is the property possessed by some elements of spontaneously emitting energy in the form of particles or waves by disintegration of their atomic nuclei.) For example, it is possible to make a molecule of water in which one of the two hydrogen atoms is a radioactive tritium (hydrogen-3) atom. This molecule behaves in almost the same way as a normal molecule of water. The main difference between the tracer molecule containing tritium and the normal molecule is that the tracer molecule continually gives off radiation that can be detected with a Geiger counter or some other type of radiation detection instrument.

One application for the tracer molecule described above would be to monitor plant growth by watering plants with it. The plants would take up the water and use it in leaves, roots, stems, flowers, and other parts in the same way it does with normal water. In this case, however, it would be possible to find out how fast the water moves into any one part of the plant. One would simply pass a Geiger counter over the plant at regular intervals and see where the water has gone.

In medicine tracers are applied, such as Technetium-99 in autoradiography and nuclear medicine, including single photon emission computed tomography (SPECT), positron emission tomography (PET) and scintigraphy.

References

It can be used in medical, or agricultural way

1. ^ Rennie M (1999). "An introduction to the use of tracers in nutrition and metabolism". Proc Nutr Soc 58 (4): 935–44. doi:10.1017/S002966519900124X. PMID 10817161. 

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