Published on

introduction to radiopharmaceuticals

Published in: Health & Medicine


  1. 1. What is Radiopharmaceuticals? A radiopharmaceutical is a radioactive compound used for the diagnosis and therapeutic treatment of human diseases. A radiopharmaceutical has two components: a radionuclide and a pharmaceutical.
  2. 2. Introduction In designing a radiopharmaceutical, a pharmaceutical is first chosen on the basis of its preferential localization in a given organ or its participation in the physiologic function of the organ. Then a suitable radionuclide is tagged onto the chosen pharmaceutical such that after administration of the radiopharmaceutical, radiations emitted from it are detected by a radiation detector.
  3. 3. Introduction Isotopes of an atom have the same number of protons, but a different number of neutrons. Radioisotopes & Radionuclides: unstable isotopes which are distinguishable by radioactive transformation.
  4. 4. Radioactivity: the process in which an unstable isotope undergoes changes until a stable state is reached . When the atomic nucleus undergoes spontaneous transformation, called radioactive decay, radiation is emitted .(alpha particles, beta particles and gamma rays).
  5. 5. Introduction Radiation refers to particles or waves coming from the nucleus of the atom (radioisotope or radionuclide) through which the atom attempts to attain a more stable configuration.
  6. 6. Important parameters + Radioactive decay is the process in which an unstable atomic nucleus spontaneously loses energy by emitting ionizing particles and radiation. +Physical half-life is the period of time required to reduce the radioactivity level of a substance to exactly one half its original value due solely to radioactive decay. biological half-life the time required for a living organism to eliminate one-half of a radioactive substance which has been introduced into it.
  7. 7. Effective half life The time required for a radioactive element in an animal body to be diminished by 50% as a result of radioactive decay and biologic elimination. Te = ( Tp X Tb) ( Tp + Tb )isotope T(ph) T(b) T(e) 3H 4500 12 12 99mTc 0.25 1 0.2 235U 26000000000 0 15 15 226Ra 580000 16000 15000
  8. 8. Ideal radiopharmaceutical properties  Short half-life isotope(Ideally 1.5 times the duration of the diagnostic procedure.)  Energy of Gamma Rays: (Ideal: 100-250 keV)  Pure gamma emitter  Target to Non target Ratio  Localization only in tissue desired  Easy preparation  Economy price
  9. 9. radioactive decay types: When an unstable nucleus decays, It may give out: 1- Alpha particle decay 2- Beta particle decay 3- Gamma ray
  10. 10. Penetrating power Alpha particles may be completely stopped by a sheet of paper, beta particles by aluminum shielding. Gamma rays can only be reduced by much more substantial mass, such as a very thick layer of lead.
  11. 11. 1- Alpha particle decay Alpha particles are made of 2 protons and 2 neutrons. This means that when a nucleus emits an alpha particle, its atomic number decreases by 2 and its atomic mass decreases by 4. Alpha particles are relatively slow and heavy and have a low penetrating power . Because they have a large charge, alpha particles ionize other atoms strongly.
  12. 12. 2- Beta particle decay Beta particles have a charge of minus 1. This means that beta particles are the same as an electron. This means the atomic mass is unchanged the atomic number increases or decreases by 1. They are fast, and light. Beta particles have a medium penetrating power. Beta particles ionize atoms that they pass, but not as strongly as alpha particles do.
  13. 13. 3- Gamma ray Gamma rays are waves, not particles. This means that they have no mass and no charge. Gamma rays have a high penetrating power Gamma rays do not directly ionize other atoms, although they may cause atoms to emit other particles which will then cause ionization.
  14. 14. Radioactive materials 1- Natural radioactivity: Nuclear reactions occur spontaneously 2- Artificial radioactivity: The property of radioactivity produced by particle bombardment or electromagnetic irradiation. All radionuclides commonly administered to patients in nuclear medicine are artificially produced
  15. 15. Types of artificial radioactivation: A- Charged-particle reactions(cyclotron) B- Photon-induced reactions(nuclear reactor) C- Neutron-induced reactions(radionuclide generator)
  16. 16. Neutron-induced reactions It is the bombardment of a nonradioactive target nucleus with a source of thermal neutrons in a device called a Radionuclide Generator.
  17. 17. Radionuclide Generator  Radionuclide generators contain a parent radionuclide that decays to produce a radioactive daughter. The parent is usually produced in specialized nuclear reactor’s.
  18. 18. Example: technetium-99m, obtained from a generator constructed of molybdenum-99 absorbed to an alumina column. Parent: 99Mo as molybdate Half-life: 66 hr. daughter: half-life:6hr
  19. 19. Application of radiopharmaceuticals 1- Treatment of disease: They are radiolabeled molecules designed to deliver therapeutic doses of ionizing radiation to specific diseased sites. 2- As an aid in the diagnosis of disease: The radiopharmaceutical accumulated in an organ of interest emit gamma radiation which are used for imaging of the organs with the help of an external imaging device
  20. 20. Good luck!