Radioisotopic Labelling

To Study the Function of Internal Organs

What is an Isotope?

  • An isotope is 2 or more elements with the same amount of protons, but different amount of neutrons
  • For ex. Carbon 12 and Carbon 13 are both isotopes of carbon, one with 6 neutrons and one with 7 neutrons
  • Isotopes do not emit rays that can be seen through a machine
  • They are short lived because of their half lives

What is a Radioisotope?

  • A Radioactive Isotope is an unstable isotope
  • They are radioactive and emit alpha, beta and gamma rays
  • They help diagnose deformities in organs by showing the shape of the organ, as well as detecting heat in the organ
  • Can be used as a poison which can kill (In 2006 Britain witnessed the apparent murder of one of its newer citizens, a former Russian intelligence official, by poisoning with radioactive polonium. His death was slow and excruciating.)
Alpha Rays
  • Very fast, large particles that are emitted during the decay of radioactive substances
  • Has a low penetrating power, so can be stopped with a sheet of paper
Beta Rays
  • Has the same weight as an electron
  • Very light particle
  • Has a medium penetrating power, takes a aluminum to stop it
Gamma Rays
  • Is a wave and burst of energy, not a particle
  • Has a high penetrating power
  • Takes a thicker sheet of metal to reduce (ex; lead or concrete)
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Most Common Radioisotope: Radionuclide/Radioactive Nuclide

  • An atom with an unstable nucleus, characterized by excess energy
  • Emit nuclear energy; specifically gamma rays
  • When a radionuclide decays its presence can be detected by the radiation it emits, thus assisting in radiotherapy
Others include:
Technetium-99m(Tc) [used to identify impeded blood flow to the heart or spread of cancer to the bones]
- Cadmium-109(Cd) [used to detect cancer]
- Europium-155(Eu) [osteoporosis detection]
  • There are numerous radioisotopes


  • Travels fast through the body, some as fast as the speed of light
  • A quick way to find a serious problem in the body
  • Elements have a huge amount of energy inside, so don't use up quickly
  • Detect cancer (one of the leading causes of death)
  • Radiotherapy can weaken or destroy particular cells in diseases like cancer


  • Very dangerous
  • Can cause infertility
  • Radioisotopes can cause cancer if exposed in high doses, therefore shouldn't be exposed in high doses

Positron Emission Tomography (P.E.T)

  • A more precise and sophisticated technology that uses isotopes produced in a cyclotron [a type of compact particle accelerator used to produce quantities of radioactive isotopes called positron emitters]
  • A radionuclide is introduced as it accumulates in the target tissue
  • It then decays and emits a positron [a subatomic particle with the same mass as an electron and a numerically equal but positive charge]
  • This process makes it easy to detect the presence or absence of radioactive materials even when in low concentration

Therefore, radioisotopic labelling is the process in which a patient receives radioisotopes through injection, inhalation or orally; which is then tracked to assist in diagnoses.