Radiation Interaction Quiz

Radiation Biology & Safety

• MRD441 course
• Offered by Universiti Teknologi MARA

Effects of Radiation at Atomic Level

• Radiation can cause excitation or ionization of atoms
• Excitation: A fraction of the radiation energy is transferred to the electron, causing it to jump to a higher energy level, farther from the nucleus
• Ionization: Radiation transfers enough energy to the electron enabling it to be completely ejected from the atom, thus leaving the atom with a positive charge (positive ion) and a free electron.

Types of Radiation

• Ionizing Radiation: Has enough energy to remove tightly bound electrons from atoms, potentially damaging DNA and cells.
  • Examples: X-rays, gamma rays, alpha/beta particles
• Non-ionizing Radiation: Lacks the energy to ionize. Generally less harmful, but can still have biological effects.
  • Examples: visible light, microwaves, radio waves, ultraviolet radiation (UV)

Ionization

• Process where high-energy radiation (e.g., X-ray photons) ejects electrons from atoms
• Leaves an ion pair (positive ion and free electron)
• Energy of the ejected electron can cause further ionizations (secondary ionization) along its path.

Linear Energy Transfer (LET)

• Measures the rate at which ionizing radiation transfers energy to surrounding tissue.
• Expressed as keV per micrometer of path length (keV/µm)
• Higher LET radiation leads to greater biological damage, lower LET radiation does less direct damage, but can lead to more damaging reactions when interacting with surrounding molecules
• High LET examples: alpha particles, beta particles, fast neutrons
• Low LET examples: X-rays, gamma rays

Relative Biological Effectiveness (RBE)

• Compares the effectiveness of a test radiation dose to a reference radiation dose.
• RBE is calculated as: D_reference/D_test (where D_referenceis the dose of the reference radiation, and D_test is the dose of the test radiation)
• Higher LET radiation often correlates with a higher RBE, meaning it's more damaging to cells.

Examples of LET Values (keV/µm)

• Cobalt-60 gamma-radiation: 0.3
• 250 kVp X-radiation: 2.
• 10 MeV protons: 4.7
• 150 MeV protons: 0.5
• Recoil protons from fission neutrons: 45.
• 14 MeV neutrons: 12.
• 2.5 MeV alpha particles: 166.
• 2 GeV Fe nuclei: 1000.

Mechanisms of Damage at the Molecular Level

• Direct Action: Radiation directly interacts with DNA, potentially causing damage
• Indirect Action: Radiation interacts with water molecules, producing free radicals that attack DNA later.

Direct Action

• Radiation directly interacts with DNA, causing mutations.
• Primarily occurs with high LET radiation (alpha particles, heavy ions).

Indirect Action

• Radiation interacts with water molecules, creating free radicals which cause damage throughout the cell.
• Primarily occurs with low LET radiation (X-rays, gamma rays)
• These free radicals can also cause damage to cellular components besides DNA.

Relationship Between LET and Action Type

• High LET radiation primarily causes direct damage to cells.
• Low LET radiation primarily causes indirect damage by creating free radicals.

Test your knowledge about the interactions of radiation with atoms, including processes such as excitation and measurement techniques like Linear Energy Transfer (LET) and Relative Biological Effectiveness (RBE). This quiz will explore key concepts in radiation physics and biology.