Electromagnetic Radiation Quiz

Radiation Types and LET

• Two categories of radiation: Low LET (e.g., gamma rays, x-rays) and High LET (e.g., alpha particles, heavy charged ions).
• LET (Linear Energy Transfer) indicates how energy from radiation deposits in tissue, affecting radiotoxicity.

Molecular Effects of Radiation

• Radiation interacts with atoms, leading to molecular changes within the body, crucial for understanding biological impacts.
• Hydrogen and oxygen are predominant in body composition, influencing radiation effects on growth and metabolism.

Molecular Composition of Body

• Major components by percentage: 80% Water, 15% Protein, 2% Lipids, 1% Carbohydrates, 1% Nucleic Acids (DNA), 1% Other.
• Four main macromolecules: Proteins, Lipids, Carbohydrates, Nucleic Acids; DNA is the most crucial and radiosensitive.

Nucleic Acids Overview

• Key nucleic acids: DNA (genetic control, heredity information) and RNA (protein synthesis).
• DNA is housed in the cell nucleus and plays a vital role in cell function.

Radiobiology

• Definition: Study of ionizing radiation effects on biological tissues, integrating biology, physics, and epidemiology.
• Aim: Ensure safer radiation use in medical diagnosis and optimize therapeutic effectiveness.

Historical Milestones in Radiobiology

• Discovery of X-rays by Wilhelm Roentgen in 1895.
• Henri Becquerel observed radioactivity in uranium in 1896.
• Pierre and Marie Curie's discovery of radium in 1898.

Radiophysics

• Biophysics applies physics principles to biological systems, a rapidly evolving interdisciplinary field.

Ionizing Radiation

• Radiation encompasses energy transmitted via particles or waves, divided into ionizing and non-ionizing types.
• Ionizing radiation can lead to excitation or ionization in biological materials.

Radiation Interaction Types

• Direct Action: When ionizing particles directly damage macromolecules (DNA, RNA, proteins), potentially leading to cell death or survivable damage if repaired.
• Indirect Action: Occurs primarily through the interaction of radiation with water, producing free radicals and ion pairs.

Free Radicals and Reactions

• Radiation interaction with water creates ion pairs (H+, OH-) and free radicals (H, OH).
• Free radicals may recombine harmlessly or create toxic substances (e.g., hydrogen peroxide) causing cellular damage.

Indirect Action Sequence of Events

• Sequence of radiation exposure: Incident X-ray photons → Fast electrons → Ion radicals → Free radicals → Macromolecular changes → Biological outcomes (cell death, mutation, carcinogenesis).

Possible Outcomes of Radiation Injury

• Potential responses include repair of damage or cell death, with variations based on the context and severity of exposure.