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A medical isotope is an isotope used in medicine. The first uses of isotopes in medicine were in radiopharmaceuticals , and this is still the most common use. However more recently, separated stable isotopes have come into use.
Radiopharmaceuticals are used in the field of nuclear medicine as radioactive tracers in medical imaging and in therapy for many diseases (for example, brachytherapy). Many radiopharmaceuticals use technetium-99m (Tc-99m) which has many useful properties as a gamma-emitting tracer nuclide.
Technetium-99m (99m Tc) is a metastable nuclear isomer of technetium-99 (itself an isotope of technetium), symbolized as 99m Tc, that is used in tens of millions of medical diagnostic procedures annually, making it the most commonly used medical radioisotope in the world.
Alpha emitters are nowadays rarely used in nuclear medicine, but were used extensively before the advent of nuclear reactor and accelerator produced radionuclides. The concepts involved in radiation exposure to humans are covered by the field of Health Physics ; the development and practice of safe and effective nuclear medicinal techniques is ...
A list of nuclear medicine radiopharmaceuticals follows. Some radioisotopes are used in ionic or inert form without attachment to a pharmaceutical; these are also included. There is a section for each radioisotope with a table of radiopharmaceuticals using that radioisotope. The sections are ordered alphabetically by the English name of the ...
99m Tc is a very versatile radioisotope, and is the most commonly used radioisotope tracer in medicine. It is easy to produce in a technetium-99m generator, by decay of 99 Mo. 99 Mo → 99m Tc + e − + ν e. The molybdenum isotope has a half-life of approximately 66 hours (2.75 days), so the generator has a useful life of about two weeks.
Several fluorescent molecules can be used simultaneously (given that they do not overlap, cf. FRET), whereas with radioactivity two isotopes can be used (tritium and a low energy isotope, e.g. 33 P due to different intensities) but require special equipment (a tritium screen and a regular phosphor-imaging screen, a specific dual channel ...
The isotope 135 I has a half-life less than seven hours, which is too short to be used in biology. Unavoidable in situ production of this isotope is important in nuclear reactor control, as it decays to 135 Xe, the most powerful known neutron absorber, and the nuclide responsible for the so-called iodine pit phenomenon.