Radtech Integrals Physics of Diagnostic Radiation Flashcards

A comprehensive set of 100 vocabulary-style flashcards covering the physics of diagnostic radiation, atomic structure, electricity, magnetism, and X-ray interactions.

Atom

The basic component and smallest unit of matter which serves as the building block of radiographer’s understanding of interactions between ionizing radiation and matter.

Atomos

Greek word meaning indivisible.

John Dalton

Scientist whose model showed that elements could be classified as to integral values of atomic mass.

Hook and eye model

John Dalton's model used to account for chemical combination.

Dmitri Mendeleev

Scientist who developed the first periodic table of elements by arranging them according to increasing atomic number.

John Joseph Thomson

Scientist who discovered the electron and described the plum pudding model.

Plum pudding model

Model where electrons are represented as negative charges (plums) in a shapeless mass of uniform positive electrification (pudding).

Robert Millikan

Scientist who calculated the charge of an electron equal to $1.60 \times 10^{-19}\,coulomb$.

Ernest Rutherford

Scientist who introduced the nuclear model describing a small dense, positively charged center called the nucleus.

Neils Bohr

Scientist who in 1913 described the atom as a miniature solar system with electrons in prescribed orbits or energy levels.

Electron

Small particle carrying one unit of negative electric charge with a mass of $9.1 \times 10^{-31}\,kg$.

Atomic mass unit (amu)

Convenient unit of mass equal to one half the mass of a carbon-12 atom.

Proton

Positively charged particle in the nucleus with a mass of $1.673 \times 10^{-27}\,kg$.

Neutron

Electrically neutral particle in the nucleus with a mass of $1.675 \times 10^{-27}\,kg$.

Eugene Goldstein

Scientist identified as the discoverer of the neutron (per transcript).

James Chadwick

Scientist identified as the discoverer of the proton (per transcript).

Nucleons

Collective term for protons and neutrons found in the nucleus.

Shells

Energy levels where electrons exist, identified by codes $K, L, M, N$, and so forth.

Electron Binding Energy (Eb)

Energy required to remove an electron from its orbit or the strength of attachment of an electron.

Valence electrons

Electrons located on the outermost shell of an atom.

Nuclide

Refers to any atomic specie.

Centrifugal Force

An outward force acting on electrons away from the center of the atom.

Centripetal Force

Also known as electrostatic force, it is the attraction between electrons and the nucleus that keeps electrons in shell.

Repulsive Force

Force occurring between protons within the nucleus.

Nuclear Binding Force

The force that holds an atomic nucleus together due to neutrons.

Atomic mass (A)

The number representing the total nucleons (protons and neutrons) in an atom.

Atomic no. (Z)

The number representing the protons or electrons in a neutrally charged atom.

Isotopes

Atoms or elements that have the same number of protons but different mass numbers.

Isobars

Atoms or elements that have the same atomic mass.

Isotones

Atoms or elements that have the same number of neutrons.

Isomers

Atoms or elements that have the same atomic mass and number but differ in energy levels.

Pauli Exclusion Formula

Formula $2(n^2)$ used to determine the maximum number of electrons that can occupy per shell.

Radioactivity

The emission of particles and energy by an unstable nucleus to reach stability.

Radioactive decay

Process where a nucleus spontaneously emits particles and energy and transforms into another atom.

Antoine Henri Becquerel

French scientist who discovered radioactivity in 1896.

Becquerel (Bq)

SI unit for radioactivity equal to $1\,disintegration/s$.

Curie (Ci)

Old unit for radioactivity equal to $3.7 \times 10^{10}\,Bq$.

Decay Constant (\lambda)

A fraction or percentage of the original number of atoms decaying per unit time.

Half-Life (T1/2)

The amount of time taken by the radioactive material to decay to $\frac{1}{2}$ of its original value.

Biological Half-life

The time required for half the amount of a substance to be eliminated from a biological system by biologic processes.

Effective Half-life

Half-life of a radioisotope in an organism resulting from combined radioactive decay and biologic excretion.

Physical Half-life

The average time required for the decay of half the atoms in a radioactive substance.

Alpha Decay

Decay where the nucleus emits a particle resembling a Helium element with mass number $4$ and charge $2$.

Beta particle

Particle with a relative charge of $-1$ and a mass of $0$ emitted during radioactive decay.

Negatron Emission

Occurs when a radioactive nuclide with a high neutron to proton ratio converts a neutron to a proton and emits an electron.

Positron Emission

Occurs when a radioactive nuclide with an excess of protons transforms a proton to a neutron and emits a positive electron.

Isomeric Transition

Decay that emits gamma rays and occurs only on elements with an excited state, reaching ground state.

Internal Conversion

The process by which a gamma ray emitted during isomeric transition transfers energy to an orbital electron, ejecting it.

Electron capture

Radioactive decay process where the nucleus captures an orbital electron to transform a proton into a neutron.

Characteristic X-ray

Produced after the ionization of an inner electron and the subsequent transition of an outer orbital electron to fill the vacancy.

Ionization

The removal or addition of an electron in an orbit.

Gamma Ray

Uncharged electromagnetic radiation of high energy and high penetrability emitted from the nucleus.

Auger process

The process of removing an electron by a characteristic x-ray within an atom.

Electron Volt (eV)

Energy acquired by an electron accelerated through a potential difference of $1\,volt$, equal to $1.6 \times 10^{-19}\,J$.

Photons

Energy disturbances that travel through space at the speed of light, also known as Quantum.

Photon wavelength

The distance from one crest to another or one valley to another.

Photon frequency

The number of wavelengths passing a point of observation per second measure in Hertz (Hz).

Hertz (Hz)

Unit of frequency equivalent to $1\,cycle/sec$.

Wave Equation

Mathematical relationship between light speed, frequency, and wavelength expressed as $c = f\lambda$.

Planck’s Quantum Theory

Describes the relationship between energy and frequency as $E = hf$.

Theory of Relativity

Einstein's theory expressed by the formula $E = mc^2$.

Inverse Square Law

Formula stating that radiation intensity is inversely proportional to the square of the distance between the source and target.

Non-ionizing radiation

Radiation not capable of ionizing the medium, such as radiofrequency, infrared, and visible light.

Ionizing radiation

Radiation capable of ionizing matter, such as x-rays, gamma rays, alpha, and beta particles.

Particulate Radiation

Radiation that travels in space possessing mass and/or charge, including alpha and beta particles.

Electromagnetic Spectrum

Distribution of electromagnetic radiation according to energy, also known as electromagnetic continuum.

Attenuation

The partial absorption of energy or total reduction in x-ray beam intensity following interaction with a medium.

Linear Energy Transfer (LET)

Measure of the rate at which energy is transferred from ionizing radiation to soft tissue, measured in $keV/\mu m$.

Range

Maximum distance traversed by ionizing radiation in an interaction medium, also known as path length.

Radon (Rn)

The largest component of terrestrial natural background radiation.

Exposure (X)

Ionization of air by x or gamma rays, measured in $C/kg$ or Roentgens (R).

Absorbed Dose (D)

Energy transferred by ionizing radiation to the interacting medium per unit mass, measured in Gray (Gy).

Equivalent Dose (H)

Radiation exposure received by radiation workers, measured in Sieverts (Sv).

Quality factor (Q)

Factor used to describe the ability of radiation to cause damage, with a value of $1$ for x and gamma rays.

Bremsstrahlung Interaction

Also known as braking radiation, results from incident electrons decelerating in the nuclear space.

Excitation

Interaction where electrons acquire energy but are not removed completely from their atom.

Classical Scattering

Interaction between low energy X-rays and atoms where the X-ray loses no energy but changes direction slightly.

Compton Effect

Interaction involving ionization of an outer shell electron, producing scattered radiation hazardous to workers.

Photoelectric Effect

Total absorption of incident X-ray during ionization of an inner shell electron, producing high contrast images.

Pair Production

Interaction involving photons with energy over $1.022\,MeV$ interacting with the nuclear field to create an electron and positron.

Photodisintegration

High energy photon interaction with the nucleus emitting nuclear fragments, requiring energy of at least $10\,MeV$.

Heel-effect

Variation in x-ray intensity across the beam due to absorption in the target heel, higher on the cathode side.

Line-focus Principle

Design allowing a large area for heating while maintaining a small effective focal spot by angling the target.

Electrification

The process of adding or removing electrons from an atom by contact, friction, or induction.

Electrostatics

The study of stationary electric charges.

Coulomb (C)

The unit of electric charge, where $1\,C = 6.3 \times 10^{18}$ electron charges.

Electrodynamics

The study of electric charges in motion, recognized as electricity.

Conductor

Any substance through which electrons flow easily, such as copper and water.

Insulator

Any material that does not allow electron flow, such as glass and clay.

Semiconductor

Material that behaves as an insulator or conductor depending on conditions, such as silicon and germanium.

Superconductor

Material property showing no resistance below a critical temperature (Tc), such as niobium.

Ampere (A)

Unit of electric current proportional to the number of electrons flowing each second.

Volt (V)

The unit of electric potential measuring the potential to do work.

Ohm’s Law

States that voltage across a circuit equals current times resistance, expressed as $V = IR$.

Electric Power

Measured in watts (W), where $P = IV$.

Series Circuit

Circuit where all elements are connected in a line along the same conductor.

Parallel Circuit

Circuit containing elements connected at their ends rather than along a single conductor line.

Resistor

Circuit element that inhibits the flow of electrons.

Capacitor

Circuit element that momentarily stores electric charge.

Transformer

Electromagnetic device that increases or decreases voltage using mutual induction (AC only).