Radioactive dating exercises
Very little radioactive material is needed in these diagnostic techniques because the radiation emitted is so easy to detect.However, therapeutic applications usually require much larger doses because their purpose is to preferentially kill diseased tissues.Radioactive isotopes have numerous medical applications—diagnosing and treating illnesses and diseases.One example of a diagnostic application is using radioactive iodine-131 to test for thyroid activity (Figure 11.4 "Medical Diagnostics").Table 11.5 "Some Radioactive Isotopes That Have Medical Applications" lists several radioactive isotopes and their medical uses.In addition to the direct application of radioactive isotopes to diseased tissue, the gamma ray emissions of some isotopes can be directed toward the tissue to be destroyed.If a once-living artifact is discovered and analyzed many years after its death, with the remaining carbon-14 compared to the known constant level, an approximate age of the artifact can be determined.Using such methods, scientists determined that the age of the Shroud of Turin (made of linen, which comes from the flax plant, and purported by some to be the burial cloth of Jesus Christ; Figure 11.3 "Shroud of Turin") is about 600–700 y, not 2,000 y as claimed by some.
The radiation emitted by some radioactive substances can be used to kill microorganisms on a variety of foodstuffs, which extends the shelf life of these products.Scientists were also able to use radiocarbon dating to show that the age of a mummified body found in the ice of the Alps was 5,300 y.Shroud of Turin In 1989, several groups of scientists used carbon-14 dating to demonstrate that the age of the Shroud of Turin was only 600–700 y.For example, if a thyroid tumor is detected, a much larger infusion (thousands of rem, as opposed to a diagnostic dose of less then 40 rem) of iodine-131 could help destroy the tumor cells.
Similarly, radioactive strontium is used to not only detect but also ease the pain of bone cancers.
The amount of radioactive iodine that collects there is directly related to the activity of the thyroid, allowing trained physicians to diagnose both hyperthyroidism and hypothyroidism.