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By the end of this section, you will be able to:
  • List common applications of radioactive isotopes

Radioactive isotopes have the same chemical properties as stable isotopes of the same element, but they emit radiation, which can be detected. If we replace one (or more) atom(s) with radioisotope(s) in a compound, we can track them by monitoring their radioactive emissions. This type of compound is called a radioactive tracer    (or radioactive label ). Radioisotopes are used to follow the paths of biochemical reactions or to determine how a substance is distributed within an organism. Radioactive tracers are also used in many medical applications, including both diagnosis and treatment. They are used to measure engine wear, analyze the geological formation around oil wells, and much more.

Radioisotopes have revolutionized medical practice (see Appendix M ), where they are used extensively. Over 10 million nuclear medicine procedures and more than 100 million nuclear medicine tests are performed annually in the United States. Four typical examples of radioactive tracers used in medicine are technetium-99 ( 43 99 Tc ) , thallium-201 ( 81 201 Tl ) , iodine-131 ( 53 131 I ) , and sodium-24 ( 11 24 Na ) . Damaged tissues in the heart, liver, and lungs absorb certain compounds of technetium-99 preferentially. After it is injected, the location of the technetium compound, and hence the damaged tissue, can be determined by detecting the γ rays emitted by the Tc-99 isotope. Thallium-201 ( [link] ) becomes concentrated in healthy heart tissue, so the two isotopes, Tc-99 and Tl-201, are used together to study heart tissue. Iodine-131 concentrates in the thyroid gland, the liver, and some parts of the brain. It can therefore be used to monitor goiter and treat thyroid conditions, such as Grave’s disease, as well as liver and brain tumors. Salt solutions containing compounds of sodium-24 are injected into the bloodstream to help locate obstructions to the flow of blood.

A photo is shown of two men, one walking on a treadmill with various wires connected to his torso region, and the other collecting blood pressure data from the first man.
Administering thallium-201 to a patient and subsequently performing a stress test offer medical professionals an opportunity to visually analyze heart function and blood flow. (credit: modification of work by “Blue0ctane”/Wikimedia Commons)

Radioisotopes used in medicine typically have short half-lives—for example, the ubiquitous Tc-99m has a half-life of 6.01 hours. This makes Tc-99m essentially impossible to store and prohibitively expensive to transport, so it is made on-site instead. Hospitals and other medical facilities use Mo-99 (which is primarily extracted from U-235 fission products) to generate Tc-99. Mo-99 undergoes β decay with a half-life of 66 hours, and the Tc-99 is then chemically extracted ( [link] ). The parent nuclide Mo-99 is part of a molybdate ion, MoO 4 2− ; when it decays, it forms the pertechnetate ion, TcO 4 . These two water-soluble ions are separated by column chromatography, with the higher charge molybdate ion adsorbing onto the alumina in the column, and the lower charge pertechnetate ion passing through the column in the solution. A few micrograms of Mo-99 can produce enough Tc-99 to perform as many as 10,000 tests.

Questions & Answers

where can I find the Arrhenius equation
onwuchekwa Reply
ln(k two/k one)= (- activation energy/R)(1/T two - 1/T one) T is tempuratue in Kelvin, K is rate constant but you can also use rate two and one instead, R is 8.314 J/mol×Kelvin
if ur solving for k two or k one you will need to use e to cancel out ln
what is an atom
Precious Reply
An atom is the smallest particle of an element which can take part in a chemical reaction..
how to find the rate of reaction?
what is isomerism ?
Lucky Reply
Formula for equilibrium
Danmori Reply
is it equilibrium constant
what us atomic of molecule
Imhologhomhe Reply
chemical formula for water
Muhammad Reply
what is elemental
Maryam Reply
what are the properties of pressure
How can water be turned to gas
what's a periodic table
Okiemute Reply
this can be defined as the systematic way of arranging element into vertical spaces called periods and horizontal spaces called groups on a table
how does carbon catenate?
obuke Reply
condition in cracking from Diesel to petrol
Brient Reply
hey I don't understand anything in chemistry so I was wondering if you could help me
Ruth Reply
i also
I also
condition for cracking diesel to form kerosene
can you tell me
please let me know
what is periodic law
rotimi Reply
periodic law state that the physical and chemical properties of an element is the periodic function of their atomic number
how is valency calculated
Ashley Reply
How is velency calculated
Hi am Isaac, The number of electrons within the outer shell of the element determine its valency . To calculate the valency of an element(or molecule, for that matter), there are multiple methods. ... The valency of an atom is equal to the number of electrons in the outer shell if that number is fou
what is the oxidation number of this compound fecl2,fecl3,fe2o3
Asmau Reply
bonds formed in an endothermic reaction are weaker than the reactants but y r these compound stable at higher temperatures
zille Reply
Practice Key Terms 5

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