CH 3 Radiation Biology

Radiation Injury

Damage caused by exposure to ionizing radiation.

Dose-Response Curve

Used to correlate the response or damage of tissues with the dose or amount of radiation received.

Stochastic Radiation Effects

Occur by chance with no threshold dose (e.g. genetic mutations and cancer).

Nonstochastic Radiation Effects

Somatic effects that have a threshold; effects increase in severity with increasing absorbed dose

Ionization

Process where x-rays displace electrons from atoms.

Free Radicals

Uncharged molecules with unpaired electrons, highly reactive.

Direct Theory

Cell damage from direct radiation impact on cells.

Indirect Theory

Cell damage via free radicals formed from water ionization.

Photoelectric Effect

Absorption of x-ray photons, transferring energy to electrons.

Compton Scatter

Scattering of x-rays, transferring energy to electrons.

Biologic Damage

Cellular harm resulting from radiation exposure.

Relative Sensitivity

Tissue's susceptibility to radiation damage.

Radiation Measurement Units

Units used to quantify radiation exposure.

Sources of Radiation Exposure

Common origins of radiation in daily life.

Risk Estimates

Calculations predicting potential harm from radiation exposure.

Somatic Effects

Effects of radiation on the body, excluding genetic.

Genetic Effects

Effects of radiation on reproductive cells.

Short-term Effects

Immediate consequences of radiation exposure (e.g. nausea, vomiting, diarrhea, hair loss, hemorrhage).

Long-term Effects

Delayed consequences of radiation exposure (e.g. cancer, birth abnormalities, genetic defects).

Chemical Changes

Alterations in molecular structure due to radiation.

Tissue Sensitivity

Vulnerability of specific tissues to radiation damage.

Dental Radiation Risks

Potential harm from radiation during dental imaging.

Linear Relationship

Response directly proportional to radiation dose.

Non-threshold Curve

Biologic damage occurs regardless of dose size.

Non-stochastic Effects

Threshold exists; severity increases with dose.

Examples of Stochastic Effects

Cancer and genetic mutations from radiation.

Examples of Non-stochastic Effects

Erythema, hair loss, cataracts, decreased fertility.

Latent Period

Time between radiation exposure and clinical signs.

Period of Injury

Variety of cellular injuries may occur.

Recovery Period

Cells may repair radiation damage over time.

Cumulative Effects

Radiation damage accumulates in tissues over time.

Total Dose

Overall amount of radiation received.

Dose Rate

Speed at which radiation is delivered.

Tissue Irradiation Amount

Extent of tissue exposed to radiation.

Cell Sensitivity

Vulnerability of cells to radiation damage.

Age Factor

Influences susceptibility to radiation injury.

Acute Radiation Syndrome

Includes nausea, vomiting, diarrhea, hair loss.

Somatic Cells

All body cells except reproductive cells.

Genetic Cells

Reproductive cells that pass traits to offspring.

Radiosensitive Cells

Cells that are more susceptible to radiation.

Radioresistant Cells

Cells that are less susceptible to radiation.

Radiosensitive Organs

Lymphoid tissue, bone marrow, testes, intestines.

Radioresistant Tissues

Salivary glands, kidney, liver.

Critical organ

An organ whose damage affects quality of life.

Skin

Critical organ exposed during dental radiography.

Thyroid gland

Critical organ sensitive to radiation exposure.

Lens of the eye

Critical organ susceptible to radiation damage.

Bone marrow

Critical organ involved in blood cell production.

Roentgen (R)

Traditional unit measuring ionization in air.

Radiation absorbed dose (rad)

Traditional unit for energy absorbed by tissue.

Roentgen equivalent man (rem)

Traditional unit for dose equivalent measurement.

Coulombs/kilogram (C/kg)

SI unit for exposure measurement.

Gray (Gy)

SI unit for radiation absorbed dose.

Sievert (Sv)

SI unit for dose equivalent measurement.

1 Gy

Equivalent to 100 rad.

1 Sv

Equivalent to 100 rem.

Milli

Prefix meaning 1/1000, used in measurements.

Natural background radiation

Ubiquitous ionizing radiation from the environment.

Cosmic radiation

Radiation from stars and the sun.

Terrestrial radiation

Radiation from earth's radioactive materials.

150 to 300 mrad

Average annual background radiation dose in the US.

Artificial radiation

Radiation from modern technology and medical procedures.

3 in 1 million

Estimated risk of fatal cancer from dental radiography.

3300 in 1 million

Spontaneous cancer development risk in individuals.

Risk versus benefit

Evaluating disease detection against radiation risks.

Film speed

Factor affecting patient exposure in dental imaging.

Digital Sensor

Modern technology used in dental radiography.

Collimation

Technique to limit radiation exposure area.

Exposure factors

Variables influencing radiation dose during imaging.