Radiation Biology Lecture Review

Flashcards covering key vocabulary, theories, measurements, and effects related to radiation biology from the lecture notes.

Radiation Biology

The study of the effects of ionizing radiation on living tissue.

Ionization (Radiation Injury)

A mechanism of radiation injury resulting when x-rays strike patient tissue, forming an ion and a dislodged electron that causes chemical changes and biologic damage.

Free Radical Formation

A mechanism of radiation injury where an x-ray photon ionizes water, forming highly reactive uncharged atoms or molecules with a single, unpaired electron in their outermost shell, which then combine to cause cell damage.

Free radical

An uncharged atom or molecule that exists with a single, unpaired electron in its outermost shell, making it highly reactive and unstable.

Direct Theory (Radiation Injury)

The theory that cell damage results when ionizing radiation directly hits critical areas within the cell, such as the nucleus (DNA).

Indirect Theory (Radiation Injury)

The theory that x-ray photons are absorbed within the cell and cause the formation of free radicals and toxins, which in turn damage the cell.

Dose-Response Curve

A graph used to correlate the damage of tissue with the amount of radiation received, often displaying a linear and nonthreshold relationship.

Linear Relationship (Dose-Response)

Indicates that the response of the tissues is directly proportional to the radiation dose.

Nonthreshold Dose-Response Curve

Suggests that some biologic damage occurs, no matter how small the amount of radiation received.

Stochastic effects

Biologic effects that are a direct function of the dose, with no dose threshold, where the effects' probability depends on the magnitude of the absorbed dose (e.g., cancer induction and genetic mutations).

Nonstochastic (deterministic) effects

Somatic effects that have a threshold, and whose severity increases with increasing absorbed dose (e.g., erythema, loss of hair, cataracts, and decreased fertility).

Latent period (Radiation Injury)

The time that elapses between exposure to ionizing radiation and the appearance of observable clinical signs.

Period of injury (Radiation Injury)

The time when actual radiation damage occurs, such as cell death, changes in cell function, or abnormal cell division.

Recovery period (Radiation Injury)

The period during which cells can repair the damage caused by radiation, if the damage is not too great.

Cumulative effects (Radiation Injury)

The additive effects of repeated radiation exposure, where unrepaired damage accumulates in tissues, potentially leading to cancer, cataracts, mutations, or leukemia.

Total dose

The total amount of radiation absorbed.

Dose rate

The speed at which radiation is delivered and absorbed.

Amount of tissue irradiated

A determining factor for radiation injury; a large area exposed is worse than a small area.

Cell sensitivity (Radiation Injury)

A determining factor for radiation injury, where cells that are replicating and young are more susceptible.

Age (Radiation Injury)

A determining factor for radiation injury, where children are more susceptible.

Short-term effects (Radiation)

Effects associated with large doses of radiation in a short amount of time, manifesting as acute radiation syndrome (nausea, vomiting, diarrhea, hair loss, hemorrhage).

Long-term effects (Radiation)

Effects seen after small doses absorbed repeatedly over a long period, appearing after years, decades, or generations (e.g., cancer, birth abnormalities, genetic defects).

Somatic cells

All cells in the body, excluding reproductive cells.

Genetic cells

The reproductive cells.

Somatic mutation

A genetic change seen in the person irradiated, but not passed on to future generations.

Genetic mutation

A genetic change not seen in the person irradiated but passed on to future generations through genetic cells.

Radiosensitive

Describes a cell that is sensitive to radiation.

Radioresistant

Describes a cell that is resistant to radiation.

Mitotic activity (Cell Sensitivity)

A factor determining cell response to radiation; cells dividing frequently or many divisions are more sensitive.

Cell differentiation (Cell Sensitivity)

A factor determining cell response to radiation; immature or non-highly specialized cells are more sensitive.

Cell metabolism (Cell Sensitivity)

A factor determining cell response to radiation; cells with higher metabolism are more sensitive.

Critical organ

An organ that, if damaged by radiation, diminishes the quality of a person’s life (e.g., skin, thyroid gland, lens of the eye, bone marrow).

Roentgen (R)

A traditional unit of radiation measurement for exposure, specifically measuring ionization in air.

Rad (Radiation absorbed dose)

A traditional unit of radiation measurement for the amount of energy absorbed by tissue (1 rad = 0.01 Gy).

Rem (Roentgen equivalent man)

A traditional unit of radiation measurement for dose equivalent, used to compare biologic effects of different kinds of radiation (1 rem = 0.01 Sv).

Coulombs/kilogram (C/kg)

An SI (newer) unit of radiation measurement for exposure.

Gray (Gy)

An SI (newer) unit of radiation measurement for absorbed dose (1 Gy = 100 rads).

Sievert (Sv)

An SI (newer) unit of radiation measurement for dose equivalent (1 Sv = 100 rems).

Exposure Measurement

The measurement of ionization in air produced by x-rays, typically using the Roentgen.

Dose Measurement

The measurement of the amount of energy absorbed by tissue, with the traditional unit being the rad and the SI equivalent being the gray.

Dose Equivalent Measurement

A measurement used to compare the biologic effects of different kinds of radiation, with the traditional unit being the rem and the SI equivalent being the sievert.

Quality factor (QF)

A dimensionless multiplier used to place the exposure effects of different types of radiation on a common scale.

Millirad (mrad)

1/1000 of a rad, used to express the small doses in dental radiography.

Millisievert (mSv)

1/1000 of a Sievert, used to express the small doses in dental radiography.

Microsievert (µSv)

1/1,000,000 of a Sievert, used to express very small doses.

Natural/background radiation

A form of ionizing radiation ubiquitous in the environment, originating from cosmic radiation (stars and sun) and terrestrial radiation (radioactive materials in the earth and air).

Human-made radiation

Ionizing radiation from artificial sources, with medical radiation being the largest contributor.

Risk vs. Benefit (Dental Radiographs)

The principle that dental radiographs should be prescribed only when the benefit of disease detection outweighs the risk of biologic damage.