Radiation Biology Definition: The study of the effects of radiation on living tissue.
Ionizing Radiation: X-rays are a form of ionizing radiation, which results in ionization when striking patient tissues. All ionizing radiations can produce biologic changes in living tissue.
Definition: Energy in the form of waves or particles moving through space (radiant energy).
Examples:
Warmth from sunlight.
Electromagnetic radiation: gamma rays, ultraviolet light, radio waves.
Particulate radiation: alpha and beta particles.
Ionization: Atoms lose or gain electrons, altering their chemical state.
Definition: Capable of changing the chemical state of matter, causing biological damage, and potentially harmful to human health.
Examples: Alpha, beta, and gamma radiation.
Definition: Bounces off or passes through matter without displacing electrons.
Harmful Effects: Unclear whether harmful to human health.
Examples: Visible light and radio waves.
Alpha Particle:
Composition: Two protons and two neutrons.
Characteristics: Heaviest type of radiation particle with a large charge.
Penetration: Doesn't travel far; cannot penetrate a sheet of paper or the surface of the skin.
Hazards: Harmful if inhaled or ingested.
Sources: Naturally occurring radioactive materials like uranium and thorium.
Beta Particle:
Composition: An electron not attached to an atom.
Characteristics: Small mass and negative charge.
Penetration: Travels farther than alpha particles; can be stopped with minimal shielding.
Effects: Can enter the body but not pass all the way through
Sources: Tritium (produced by cosmic radiation) and Carbon-14 (used in carbon-dating).
Neutron:
Composition: Particle with no charge in the nucleus of an atom.
Characteristics: Does not interact well with materials, travels a long way.
Shielding: Requires large quantities of water or light atom materials to stop.
Sources: Nuclear fission in a nuclear reactor (splitting of uranium atoms).
Electromagnetic Radiation (X-rays and Gamma Rays):
Characteristics: More energy than sunlight, no mass or charge.
Penetration: Can penetrate through the body.
Uses: Medical treatments.
Energy Levels: Vary from low (dental x-rays) to very high (sterilizing medical equipment).
Shielding: Dense materials like concrete and lead.
Definition: Radioactive isotopes of an element.
Isotopes: Same number of protons but differing numbers of neutrons.
Characteristics: Unstable combination of neutrons and protons, or excess energy in their nucleus (nuclei are unstable and spontaneously emitting excess energy).
Example: Hydrogen isotopes (hydrogen-3/tritium is radioactive).
Occur naturally or by artificially altering the atom.
Produced in nuclear reactors.
Example: Uranium (uranium-238 is most abundant, uranium-235 is more radioactive).
Process: Unstable nucleus regains stability by shedding excess particles and energy in the form of radiation.
Half-life: Unique time period for each radioisotope to undergo radioactive decay (time it takes for half of the unstable atoms to decay).
Medical Value: Used in diagnosis and treatment of disease.
Natural Background Radiation:
Sun.
Earth.
Atmosphere.
Artificial Radiation:
Man-made.
Medical/dental x-rays.
Nuclear sources.
Consumer products/activities.
Radioactive materials reach people via various routes.
Examples:
Airborne radioactive material falling on pasture, eaten by cows, present in milk, consumed by people.
Inhalation of radioactive material.
Radioactive material in water, exposure through fish consumption or swimming.
Radiation causes ionization of atoms, which affects:
Molecules.
Cells.
Tissues.
Organs.
The whole body.
Direct Effects:
Radiation interacts directly with atoms of the DNA molecule or other critical cellular components.
May affect the ability of a cell to reproduce and survive.
Infrequent due to the small proportion of critical components in the cell.
Direct interaction with an active cell results in cell death or mutation; less effect on dormant cells.
Indirect Effects:
Ionizing radiation breaks bonds that hold the water molecule together, producing toxic substances (radicals like hydroxyl OH, superoxide anion O2−$$O_2^{-}$$, etc.).
These radicals lead to cell destruction.
Frequent occurrence because body cells are mostly water (70-80%).
X-ray photons interact with water in cells, leading to ionization and free radical formation.
Free radicals also formed by UV light, air pollution, ionizing radiation, inflammation, metabolism, and smoking.
Prodromal Period:
Symptoms: Nausea, vomiting, loss of appetite, possible diarrhea (dose-dependent).
Timing: Minutes to days following exposure; symptoms last minutes to days.
Latent Period:
Time between exposure and appearance of radiation damage.
Varies depending on:
Total dose of radiation received.
Rate of dose delivery.
More radiation + faster dose rate = shorter latent period.
Period of Injury:
Cell injuries:
Cell death.
Changes in cell/tissue/organ function.
Breaking or clumping of chromosomes.
Formation of giant cells.
Abnormal or stopped cell division.
Recovery Period:
Not all injuries are permanent.
Most low-level radiation damage is repaired within the body's cells.
Scatter radiation clears in 24-48 hours.
Repeated exposure doesn't allow for adjustment.
Dose Rate: How fast the dose is received. A dose received over time is less severe than the same dose received all at once. High dose rates don't allow time for repair.
Dose Location: Impact less severe if only part of the body receives the dose.
Sensitivity: Fetus is most vulnerable. Infants, children, elderly, pregnant women, and immunocompromised individuals are more vulnerable. Rapidly dividing cells are more susceptible.
Additive effects of radiation exposure; unrepaired damage builds up.
Can lead to: Cancer, cataract formation, birth defects.
Short Term: High doses over short periods kill cells, leading to death, skin burns, hair loss, sterility, cataracts.
Long Term: Low doses over extended periods cause chronic effects that may not be observed for years.
Germ cells (sperm and ova): Genetic abnormalities in offspring.
Somatic cells: Diseases including cancer (carcinogenesis).
Oncogenes affect cancer incidence.
Somatic Effects:
Occur in all body cells except reproductive cells.
Not passed to future generations.
Only affect the individual exposed.
Primary consequence is cancer.
Genetic Effects:
Occur in reproductive cells.
Passed to future generations.
Do not affect the exposed individual.
Genetic damage cannot be repaired.
Cells most sensitive at or close to M (mitosis).
G2 phase as sensitive as M phase.
Resistance greatest in the later part of S phase.
G1 phase has resistant period early, sensitive period late.
Mitotic Death:
Cells die attempting to divide, primarily due to asymmetric chromosome anomalies.
Most common mechanism.
Apoptosis:
Programmed cell death.
Cell separation in apoptotic bodies.
Bystander Effect:
Cells directly affected release cytotoxic molecules, causing death in neighboring cells.
Single-Strand Breaks:
Little biologic consequence because repaired readily using the opposite strand as a template.
Often repairable.
Double-Strand Breaks:
Most important lesions produced in chromosomes by radiation.
Interaction of two double-strand breaks may result in cell killing.
Lethal.
Diagnostic Radiology:
Diagnostic.
Radiotherapy:
Treatment.
Nuclear Medicine:
Diagnostic.
Treatment.
Lab tests.
Produce an anatomical or functional patient image (using x-rays) which is clinically useful while delivering as low a radiation dose as possible.
X-ray picture of the breast.
Uses a small dose of ionizing radiation.
Detects early signs of breast cancer.
Best test for early detection (up to three years before physical detection).
Uses radioactive isotopes.
Radioisotope tracer is taken orally, injected, or inhaled.
Circulates through the body or taken up by certain tissues.
Distribution tracked by emitted radiation.
Captured by imaging techniques.
Radioisotopes have short half-lives, decay before causing damage.
Tells how well the heart pumps and how much blood is pumped with each heartbeat.
Radioactive tracer injected into arm vein.
Tracer “tags
Radiation Biology Flashcards
Alpha Particle:
Beta Particle:
Neutron:
Electromagnetic Radiation (X-rays and Gamma Rays):
Natural Background Radiation:
Artificial Radiation:
Direct Effects:
Indirect Effects:
Prodromal Period:
Latent Period:
Period of Injury:
Recovery Period:
Mitotic Death:
Apoptosis:
Bystander Effect:
Diagnostic Radiology:
Radiotherapy:
Nuclear Medicine: