X-Ray Physics & Radiation Safety – Vocabulary Review

Vocabulary flashcards covering parts of the x-ray machine, atomic structure, radiation physics, biological effects, and radiation protection as outlined in the lecture notes.

Control Panel

Part of the x-ray machine that houses the on/off switch, indicator light, exposure button, and settings that regulate the x-ray beam.

Extension Arm

Movable support that suspends the x-ray tubehead and positions it around the patient.

Metal Housing

Lead-lined protective casing around the x-ray tube that shields and grounds the high-voltage components.

Aluminum Filter (Filtration Disk)

Aluminum sheet (≈2.5 mm thick) placed in the path of the x-ray beam to remove low-energy, longer-wavelength photons.

Matter

Anything that occupies space and has mass.

Atom

Fundamental unit of matter composed of a nucleus (protons & neutrons) surrounded by electrons.

Atomic Number (Z)

Number of protons in the nucleus; identifies the element.

Atomic Weight / Mass Number (A)

Total number of protons plus neutrons in an atom’s nucleus.

Electron

Negatively charged subatomic particle (charge = –1).

Maximum Electron Shells

Atoms can possess up to seven electron shells or energy levels.

Electron Shell Names

K, L, M, N, O, P, Q shells; K shell has the strongest binding energy, Q the weakest.

Binding Energy

Electrostatic force that holds electrons in their orbits around the nucleus.

Molecule

Two or more atoms joined by chemical bonds.

Neutral Atom

Atom with equal numbers of protons and electrons, yielding no net charge.

Ion Pair

Set formed when an atom loses an electron (positive ion) and the ejected electron (negative ion).

Radiation

Energy transmitted through space or matter as waves or particles.

Ionizing Radiation

Radiation capable of removing orbital electrons; includes particulate and electromagnetic forms.

Particulate Radiation

Ionizing radiation consisting of particles (e.g., electrons, protons, alpha particles).

Electromagnetic Radiation

Ionizing or non-ionizing energy that travels as waves at the speed of light (e.g., x-rays, gamma rays).

Velocity

Speed of a wave; for electromagnetic radiation, 3 × 10⁸ m/s (speed of light).

Wavelength

Distance between two successive crests of a wave; measured in nanometers or angstroms.

Frequency

Number of wave crests that pass a point per second; measured in hertz (Hz).

Primary Radiation

Useful x-ray beam emitted directly from the tubehead target.

Secondary Radiation

Radiation created when primary beam interacts with matter (e.g., patient tissues).

CATNAP

Acronym: Cathode-Anode-Target Negative-Anode Positive; reminds that electrons travel from the negative cathode to the positive anode target.

Cathode

Negative electrode of the x-ray tube containing the filament that emits electrons.

Anode

Positive electrode of the x-ray tube that contains the tungsten target where x-rays are produced.

Voltage (Potential Difference)

Force that moves electrons between two points; measured in volts (V or kVp).

Amperage

Quantity of electrons flowing; measured in amperes (mA).

Thermionic Emission

Release of electrons from the heated tungsten filament at the cathode.

Compton Scatter

Interaction in which an x-ray photon ejects an outer electron, producing ionization and a scattered, lower-energy photon.

Stochastic Effect

Radiation effect whose probability, not severity, increases with dose (e.g., cancer).

Non-Stochastic (Deterministic) Effect

Effect whose severity increases with dose after a threshold (e.g., skin erythema, cataract).

Total Dose

Sum of all radiation received; higher total dose equals greater biological damage.

Dose Rate

Rate at which radiation is delivered; higher rates cause more damage than the same dose given over time.

Amount of Tissue Irradiated

Larger exposed volumes result in greater total damage.

Cell Sensitivity

Rapidly dividing, undifferentiated cells are more radiosensitive than mature, specialized cells.

Age (Radiation Sensitivity)

Younger individuals are more sensitive to radiation effects than adults.

Somatic Mutation

Radiation-induced change in somatic (body) cells; affects the individual (e.g., skin cancer).

Genetic Mutation

Change in reproductive cells; may be passed to offspring (e.g., inherited disorders).

Roentgen (R)

Traditional unit measuring exposure in air; quantity of ionization produced by x-rays in air.

Collimator

Lead diaphragm that shapes and restricts the size of the x-ray beam.

Rectangular Collimator

Beam-restricting device that most effectively reduces patient exposure by limiting the beam to film size.

Latent Period

Time between radiation exposure and appearance of observable biological effects.

Period of Injury

Interval during which cellular damage (ionization, free radicals) actually occurs.

Recovery Period

Time when cells repair radiation damage; may be complete or lead to cumulative effects.

Radioresistant Cells

Cells least affected by radiation, e.g., muscle and nerve tissue.

Radiosensitive Cells

Cells most susceptible to radiation, e.g., small lymphocytes, bone marrow, reproductive cells.

Critical Organs (Dental Radiography)

Skin, thyroid gland, lens of the eye, bone marrow—damage to these significantly impacts quality of life.

RAD (Radiation Absorbed Dose)

Traditional unit describing the amount of energy absorbed per gram of tissue.