Radiation Basics: EMR, Dosimetry, and X-ray Discovery (Vocabulary Flashcards)

Vocabulary flashcards covering key terms and concepts from the lecture notes on radiation, EMR, dosimetry, and X-ray discovery.

Absorbed Dose

Amount of radiation energy deposited in a unit mass of tissue. Unit: Gray (Gy).

Gray (Gy)

SI unit of absorbed dose; 1 Gy = 1 joule absorbed per kilogram of matter.

Air Kerma

Kinetic energy released per unit mass in air; used to describe the energy delivered to a point by ionizing radiation.

ALARA

As Low As Reasonably Achievable; principle to minimize radiation exposure.

Equivalent Dose

Absorbed dose adjusted for the type of radiation to reflect its biological effect; commonly expressed in rem or Sv.

Effective Dose

Sum of the weighted equivalent doses to all tissues, reflecting varying tissue sensitivities; unit: Sievert (Sv).

Electromagnetic Radiation

Radiation that has both electric and magnetic components and can behave as waves and particles (e.g., X-rays).

Exposure

Measure of ionization in air caused by radiation; historically expressed as Roentgen (R) or Coulomb/kg.

Fluorescence

Instantaneous light emission by a material when exposed to energy (e.g., barium platinocyanide coating glowing under X-rays).

Roentgen (R)

Unit of exposure in air, used historically to quantify ionizing radiation in air.

Rem

Roentgen Equivalent Man; old unit of dose equivalent, related to biological effect (1 Sv ≈ 100 rem).

Sievert (Sv)

SI unit of dose equivalent, reflecting the biological effect of radiation.

Photon

A quantum (packet) of electromagnetic energy; X-rays are photons with high energy.

Quantum

A discrete unit of energy; in radiation, the photon is a quantum of EM energy.

Radioactivity

Unstable atoms spontaneously emit particles and energy from the nucleus to reach stability.

Wavelength (lambda)

Distance between successive crests (or troughs) of a wave; commonly measured in angstroms (Å) or nanometers (nm).

Frequency

Number of wave cycles passing a point per unit time; unit: Hertz (Hz).

Speed of Light

Constant c, where c = λν; in vacuum c ≈ 3.0 × 10^8 m/s; electromagnetic waves travel at this speed.

Electromagnetic Spectrum

Range of EM radiation from radio waves to gamma rays; X-rays and gamma rays are high-energy portions used in imaging and therapy.

X-ray

A form of electromagnetic radiation with wave-particle duality; used for imaging and produced in X-ray tubes.

Crookes Tube

Glass evacuated tube used by Roentgen to generate X-rays; contains electrodes that produce cathode rays.

Roentgen

Dr. Wilhelm Conrad Roentgen, German physicist who discovered X-rays on November 8, 1895; Nobel Prize in Physics in 1901.

Barium Platinocyanide

Phosphorescent material Roentgen used to visualize X-ray-induced glow on paper.”

KVP (Kilovolt Peak)

Control for penetrating power of X-ray beam; affects beam quality and energy.

mA (Milliamperage)

Tube current; affects the number of X-ray photons produced per unit time.

mAs

Product of mA and exposure time; correlates with total X-ray exposure.

X-ray Energy Range for Medical Use

Typically about 30–150 kVp, defining the useful range of X-ray energies for diagnostic imaging.

Erythema

Redness or burning of the skin caused by exposure to radiation.

Secondary Radiation

Radiation produced as a result of primary X-ray interactions with matter.

Inverse Relationship: Wavelength and Frequency

Shorter wavelength corresponds to higher frequency and higher energy; c = λν describes their relationship.