Radiation: Types, Sources, and Effects

Radiation: Types, Sources, and Doses Received

• Radiation exists in various types and sources.
• Some types of radiation cause damage to biological tissues, while others do not.
• Sources include natural (always present) and human-made (created for specific purposes).
• Both contribute to the total radiation humans receive throughout their lives.

Radiation

• Radiation is the ability to perform work, essentially moving an object against resistance.
• Radiation represents energy transfer from one location to another, manifesting in numerous ways.

Types of Radiation

• Radiation types include mechanical vibrations (e.g., ultrasound) and electromagnetic waves (e.g., radio waves, microwaves, infrared, visible light, ultraviolet, X-rays, gamma rays).

The Electromagnetic Spectrum

• The electromagnetic spectrum encompasses the entire range of frequencies and wavelengths of electromagnetic waves.
• Higher energy radiation has shorter wavelengths and higher frequencies, vice versa.
• Calculation of wavelength and energy of radiation is detailed in the textbook.

Electromagnetic Waves

• Electromagnetic waves involve fluctuating electric and magnetic fields traveling through space.
• Waves are characterized by frequency and wavelength.
• Radiation can behave as a wave and a particle (wave-particle duality).

Ionizing and Nonionizing Radiation

• Radiation is divided into ionizing and nonionizing types based on its ability to ionize matter.
• Ionizing radiation (energy > 10 eV) has enough energy to remove electrons from atoms, causing ionization. Examples: X-rays, gamma rays, high-energy ultraviolet radiation
• Nonionizing radiation (energy < 10 eV) has insufficient energy to cause ionization and does not typically damage biological tissues, examples include: visible light, infrared rays, microwaves, and radio waves.

Ionizing Radiation

• Ionization is the process where radiation removes an atom's electrons, converting it into an ion.
• Ionization makes radiation useful for medical imaging.
• Excessive ionizing radiation can cause damage to biological material.
• Radiation dose is the amount of energy transferred to electrons.

Particulate Radiation

• Particulate radiation encompasses subatomic particles like alpha particles, beta particles, neutrons, and protons that are ejected from atoms at high speeds.
• Ionization occurs through direct atomic collisions.
• No ionization occurs if subatomic particles are at rest.

Alpha Particles

• Alpha rays are emitted from heavy radioactive elements during decay, containing two protons and two neutrons.
• They are helium nuclei and possess a significant mass and positive charge.
• Alpha particles are less penetrating than beta particles, losing energy quickly and traveling short distances in biological matter.
• Considered virtually harmless externally, but extremely damaging internally.

Beta Particles

• Beta rays are similar to high-speed electrons, lighter than alpha particles, and carrying a single negative electric charge.
• They interact moderately with their surroundings and are more penetrating than alpha particles, traveling further in biological matter.
• Requires more substantial shielding to absorb.

Protons

• Protons are positively charged components of atoms with a relatively small mass that is 1800 times greater than an electron's.
• The number of protons determines the atomic number.

Neutrons

• Neutrons are electrically neutral components of atoms, with approximately the same mass as a proton.
• Isotopes have the same number of protons but different numbers of neutrons, leading to stable or unstable nuclei (radioisotopes).

Introduction to the Concept of Radiation Dose

• Absorbed dose is the amount of kinetic energy absorbed per unit mass due to ionizing radiation.
• Measured in milligray (mGy.)

Equivalent Dose (EqD)

• Accounts for the type of ionizing radiation and provides an overall dose value, considering tissue interaction differences.
• Measured in millisieverts (mSv).

Effective Dose (EfD)

• Accounts for the dose of all ionizing radiation types across various organs/tissues.
• Provides an estimate of overall harm potential from a given absorbed dose.
• Measured in millisieverts (mSv).

Biologic Damage Potential

• Ionizing radiation primarily damages living organisms by ejecting electrons from atoms within tissues.
• This results in molecular, cellular and organic damage.

Sources of Radiation (Natural)

• Natural radiation (background radiation) includes terrestrial radiation (e.g., radon-222).
• Solar and galactic cosmic radiation.
• Internal radiation from radioactive atoms (radionuclides).
• Tables in the textbook provide average annual radiation equivalent doses per person.

Sources of Radiation (Human-Made)

• Human-made (artificial) radiation sources include radioactive materials in consumer products, nuclear fuel and power generation.
• Nuclear weapon testing fallout, nuclear power plant accidents (TMI-2, Chernobyl, Fukushima).

Medical Radiation

• Medical exposures from diagnostic X-rays and radiopharmaceuticals are common sources.
• Computed Tomography (CT) and radiography/fluoroscopy are significant contributors to annual doses (averaging 2.3 mSv for medical radiation).
• Patient doses vary due to imaging equipment variability and technician/radiologist skills.
• ESE, Bone marrow, and gonadal doses are measured separately to assess exposure in diagnostic procedures.