Radiation Safety and Protection Practice Flashcards

Comprehensive practice flashcards covering radiation safety, target and matter interactions, dosimetry units, radiobiology, and shielding principles based on the lecture notes.

Justification

The principle that there must be a benefit associated with any radiation procedure or exposure.

Optimization

The principle of keeping all radiation exposures as low as reasonably achievable (ALARA).

Dose Limitation

Established radiation dose limits, such as the occupational whole body limit of $50\,mSv$.

Occupational Exposure

Radiation exposure received during the course of work activities.

Medical Exposure

Radiation exposure received during diagnostic or therapeutic medical procedures.

Public Exposure

Exposure to natural sources of radiation, such as radon gas.

Thermionic emission

The process of releasing free electrons from a heated tungsten filament at the cathode; controlled by mA.

Focusing cup

A component made of molybdenum or nickel used to focus the electron stream toward the focal spot on the anode.

Anode

The component (typically tungsten) where electrons are rapidly decelerated to produce x-ray photons; $99\%$ of energy is absorbed as heat and $1\%$ is created into x-rays.

Target interactions

Interactions occurring at the anode inside the x-ray tube that start with an electron and produce an x-ray photon.

Matter interactions

Interactions occurring at the patient level that start with an x-ray photon.

K-shell capacity

The electron shell closest to the nucleus; it can hold up to $2$ electrons and has the least amount of energy.

Octet Rule

The preference of an atom to have eight electrons in its valence shell.

Bremsstrahlung radiation

Known as 'braking' radiation, it produces x-rays of all energies and accounts for $90\%$ of all x-ray production ($100\%$ below $70\,kVp$).

Characteristic Radiation

Created when an incident electron collides with a K-shell electron, causing a cascade effect as electrons fall into inner shells.

Tungsten K-shell binding energy

$69.5$ or $70\,keV$.

Inverse Square Law

States that the intensity of radiation is inversely proportional to the square of the distance between the source and the receptor.

Quality (X-ray beam)

Refers to the energy and penetrability of x-ray photons, determined by $kVp$.

Quantity (X-ray beam)

Refers to the number of x-ray photons or beam intensity, determined by $mAs$.

Photoelectric Effect

The matter interaction where total absorption of the x-ray photon occurs; it is the main source of radiation dose to the patient.

Compton Scatter

The matter interaction where a photon's energy is partially absorbed by an outer shell electron, causing ionization; the source of most occupational exposure and image fog.

Coherent Scatter

A rare interaction at low energy ($10\,keV$) where a photon enters and exits as a scatter photon with no effect on dose; also called Classical scatter.

Attenuation

The reduction in x-ray beam intensity as it passes through matter, involving both absorption and scattering.

Alpha particle

The heaviest type of radiation particle (e.g., Radon), which can be stopped by a single sheet of paper.

NCRP Chart #160

Addresses radiation exposure in the US, noting that medical imaging is the largest source ($~50\%$) of total exposure.

Exposure in Air

Direct measurement of ionizations in air molecules, calculated in $Coulomb/kg$.

Air Kerma

The kinetic energy released in matter or energy of ionization in air, measured in Gray ($Gy_a$).

Absorbed Dose

The energy absorbed in matter per unit mass, measured in Gray ($Gy_t$).

Equivalent Dose (EqD)

Calculated dose in Sieverts ($Sv$) that accounts for the relative biological effectiveness ($W_R$) of the radiation type: $Sv = Gy \times W_R$.

Effective Dose (EfD)

Calculated dose in Sieverts ($Sv$) that accounts for the radiation type ($W_R$) and the radiosensitivity of the specific tissue ($W_T$).

Law of Bergonie and Tribondeau

States that a cell's radiosensitivity is directly proportional to its reproductive rate and inversely proportional to its degree of differentiation.

Mitosis phase

The most radiosensitive phase of the cell cycle, with sensitivity $10$ to $100$ times greater than non-dividing phases.

Lymphocytes

The most radiosensitive blood cells in the body.

Oxygen Enhancement Ratio (OER)

The phenomenon where tissue is more sensitive to radiation when in an oxygenated state due to the creation of free radicals.

Indirect Radiation Damage

The most common mechanism in humans where radiation interacts with water (radiolysis) to produce free radicals that damage DNA.

Linear Energy Transfer (LET)

The rate at which radiation energy is deposited in tissue per unit length ($um$); alpha particles have higher LET than x-rays.

LD 50/30

The whole body radiation dose necessary to kill $50\%$ of the exposed population within $30$ days.

Stochastic effects

Random, non-threshold effects (e.g., cancer, leukemia) where the dose determines the chance of getting the effect but not its severity.

Deterministic effects

Also called tissue reactions; non-random effects (e.g., skin erythema, cataracts) that have a threshold and whose severity increases with dose.

Hematopoietic syndrome

An acute radiation syndrome occurring between $1$ and $10\,Gy$ that causes death within $3$ to $6$ weeks due to blood organ depression.

Gastrointestinal death

An acute radiation syndrome occurring between $10$ and $50\,Gy$ primarily affecting the small bowel, with death in about $1$ week.

Central nervous system syndrome

An acute radiation syndrome occurring at whole body doses above $50\,Gy$, affecting the brain and causing death within hours or days.

Automatic Exposure Control (AEC)

A device located between the patient and the IR that determines exposure time; its safety backup timer is usually set to $150\%$ to $200\%$ of the expected time.

Total Filtration

The sum of inherent and added filtration; for equipment above $70\,kVp$, the requirement is $2.5\,mm\,Al$ equivalent.

Primary Barrier

Shielding (typically $1/16$ inch lead) located where the primary beam is directed, extending to a height of $7\,feet$..

Secondary Barrier

Shielding (typically $1/32$ inch lead) that protects against scatter and leakage radiation, such as the x-ray control booth window.

Optically stimulated luminescence (OSL)

A dosimeter containing aluminum oxide that emits light when exposed to a laser; it provides a permanent record of radiation dose.

Annual Whole Body Dose Limit

The occupational equivalent limit set at $50\,mSv$ per year.

Fetal dose limit

The limit for the entire gestation period is $5\,mSv$, or $0.5\,mSv$ per month.

Material Safety Data Sheet (MSDS)

A document providing safety guidelines for chemicals and materials, including toxicity, PPE requirements, and disposal instructions.