wk4 intro to radiation and radiation protection

This set of vocabulary flashcards covers the fundamentals of ionising radiation, its biological effects, types of exposure, units of measurement, and principles of radiation protection based on the MRSC1350 lecture.

Ionisation

The process in which an electron is given enough energy to break away from an atom, resulting in the formation of 2 charged particles or ions.

X-Rays

Electromagnetic radiation produced by electrons external to the nucleus or when electrons strike a target; used in diagnostic radiography and radiation therapy.

Gamma rays

High energy electromagnetic radiation emitted from an excited nucleus after it undergoes radioactive decay, capable of passing through many different materials.

Alpha particles

Particles composed of 2 protons and 2 neutrons tightly bound, emitted from the nucleus during radioactive decay; they are highly ionising but have low penetration.

Beta (-ve) particles

High speed electrons ejected from the nucleus during radioactive decay when there are too many neutrons; they are more penetrating but less ionising than alpha particles.

Beta (+ve) / Positrons

Particles emitted from unstable radioisotopes that have too few neutrons; they annihilate if they come too close to an electron, converting into 2 gamma rays emitted in opposite directions.

Stochastic (Probabilistic) Effects

Radiation-induced effects where the probability of damage (such as cancer induction or hereditary effects) is related to the dose, governed by statistical probabilities.

Linear, no-threshold (LNT) hypothesis

The presumption that the proportion of risk and dose observed at higher levels continues through all lower levels of dose down to zero.

Radiation Hormesis

The theory that low doses of radiation are not necessarily bad for an organism.

Non-Stochastic (Deterministic) Effects

Dose-related effects that occur once a specific threshold is exceeded, where the severity of the damage increases as the radiation dose increases.

Hemopoietic syndrome

An acute syndrome of total body irradiation affecting the bone marrow, characterized by immunosuppression and bleeding.

Gastrointestinal syndrome

An acute syndrome caused by radiation dose resulting in intestinal ulcers and a nonfunctional gut.

Cerebrovascular syndrome

A severe acute syndrome resulting from extreme radiation doses, causing nausea, vomiting, coma, and death within $2-3$ days.

Law of Bergonie and Tripondeau

A law stating that radiosensitivity is a function of the metabolic state of the cell being irradiated; sensitivity is higher in young, immature cells with high metabolic rates.

Absorbed Dose (D)

A measure of the amount of energy transfer, expressed in Gray ($Gy$).

Dose equivalent (H)

A measure of biological effect expressed in Sieverts ($Sv$), calculated by multiplying the absorbed dose by a factor for the specific type of radiation.

Effective dose (E)

The sum of dose equivalents multiplied by factors for specific organs to account for their radiosensitivity, expressed in Sieverts ($Sv$).

Bequerel [Bq]

A unit used to measure the activity of a radioactive source.

Cosmic radiation

Residual background radiation in space left over from the Big Bang; dose rates increase with altitude.

Terrestrial radiation

Natural radioactivity found in rocks and soil.

Ramsar, Iran

The location with the highest known background radiation in the world, due to $^{226}Radium$ brought to the surface by hot springs.

Justification

The ICRP principle stating that the benefit of using radiation must outweigh the risk.

Optimization (ALARA)

The ICRP principle of keeping radiation doses As Low As Reasonably Achievable.

Newton’s inverse square law

The law stating that radiation intensity decreases with distance; doubling the distance reduces the dose by a factor of four.

HVL (Half Value Layer)

The thickness of a material required to reduce the number of radiation photons to one-half of their initial number.

Tungsten (W)

A high atomic number, high-density material used for shielding, such as in PET syringe shields where a $14 ext{ mm}$ thickness decreases finger dose by approximately 97 ext{%}.

Thermoluminescent Dosimeter (TLD)

A device used by medical radiation workers to measure occupational exposure; it stores energy from radiation which is released as light when the device is heated.