Lecture 1

Types of Radiation

• Ionizing Radiation: Involves the ejection of one or more orbital electrons from atoms.
• Localized Energy Radiation: Releases large amounts of energy in a confined area per event.
• High-Energy Transfer: Can transfer sufficient energy to orbital electrons to remove them from atoms.
• Wave-Particle Duality: Travels through space as waves but interacts with matter as particles of energy.
• Alpha Radiation: Consists of two protons and two neutrons, emitted during the decay of heavy radionuclides.
• Positively Charged Radiation: Used in cancer treatments, typically associated with alpha particles.
• Electrically Neutral Radiation: Produced through acceleration processes or nuclear fission, such as gamma rays.
• Therapeutic Radiation: Requires high energy for production and is utilized in radiation therapy.
• Cancer Treatment Radiation: Can be accelerated to high energy, emphasizing its use in oncology.
• Risks to Astronauts: High-energy ions pose risks, particularly related to retinal exposure.

Sources and Effects of Radiation

• Non-Natural Sources: Certain types of radiation, such as specific medical treatments, can be categorized as not being naturally occurring.
• Potency Determinant: The main factor influencing the potency of ionizing radiation is its type and energy.
• Man-Made Sources: Examples like nuclear power plants or medical imaging technologies are considered man-made sources of ionizing radiation.
• Historical Exposure Sources: Historically, natural background radiation contributed significantly to overall exposure levels.
• Medical Radiation: The primary source of radiation exposure in medical contexts is diagnostic imaging procedures.
• Collective Effective Dose: Between 2006 and 2016, there was a notable change in the collective effective dose of radiation exposure as reported in 2019 by the NCRP.

Research and Discoveries

• Shift in Radiation Exposure: The significant change in radiation exposure in the US is mainly attributed to advancements in medical technology and imaging.
• Study of Biological Effects: The discovery of X-rays by Wilhelm Conrad Röntgen marked the beginning of studying the biological effects of ionizing radiation.
• Pioneering Research: Marie Curie conducted pioneering studies on radioactivity and its potential health hazards.
• Post-Event Research: Events like the Atomic Bombings of Hiroshima and Nagasaki and the Chernobyl disaster spurred intensive research into radiation's biological effects, providing vital data on exposure consequences.
• 1920s Use of Radium: Radium and other radioactive substances were used for various therapies, reflecting a historical misunderstanding of their biological risks.
• Radiation-Tissue Interactions: Types of interactions include ionization, excitation, and energy transfer between ionizing radiation and tissue atoms.
• Key Historical Incidents: Incidents such as the Chernobyl disaster and the bombings in Hiroshima and Nagasaki occurred in 1986 and 1945, respectively.
• World War II Research: The crisis during World War II led to intensive research on the biological effects of radiation, focusing on understanding its impacts.