Radiologic Physics and X-ray Imaging Systems

These flashcards cover basic physics principles, atomic structure, nuclear arrangements, radioactivity, x-ray production, interactions with matter, and the components and operation of x-ray imaging systems including transformers, timers, and tube assemblies.

Mass

A measure of an object's inertia or resistance to acceleration, measured in $kg$.

Velocity

The constant speed of a body moving in a given direction, measured in $m/s$.

Acceleration

The rate of change of velocity, measured in $m/s^2$.

Electric charge of e- & p+

The fundamental charge value expressed as $1.6 \times 10^{-19}$ coulomb.

Electric current

The flow of electrons through a circuit, measured in amperes ($A$); defined as the amount of charge that flows divided by time ($1A = 1C/\text{second}$).

Newton's First Law of Motion

Also known as the Law of Inertia, it states an object remains at rest or moves at a constant velocity unless acted upon by an external force.

Newton's Second Law of Motion

The vector sum of forces $F$ on an object equals the mass $m$ multiplied by the acceleration vector $a$ ($F = ma$).

Newton's Third Law of Motion

For every action, there is always an equal but opposite reaction.

Atom

The basic component and the smallest unit of matter.

Nucleus

The central core of an atom containing nearly all its mass and composed of nucleons (protons and neutrons).

Nucleons

A collective term for protons (positively charged) and neutrons (neutral particle) found in the nucleus.

John Dalton Model

Described the atom using a 'hook and eye' model.

JJ Thomson Model

Described the atom using a 'plum pudding' model.

Dmitri Mendeleev

Developed the 1st table of elements.

Ernest Rutherford Model

Proposed the nuclear model of the atom.

Neils Bohr Model

Described the atom as a miniature solar system.

Electron Binding Energy

The energy possessed by an electron in its orbit, representing the strength of attachment to its shell and the energy required to remove it.

Isotopes

Atoms or elements that have the same number of Protons.

Isobars

Elements that have the same Atomic mass.

Isotones

Different elements that have the same number of Neutrons.

Isomers

Elements that have the same atomic mass and atomic number but differ in Energy levels.

Becquerel (Bq)

The SI unit of radioactivity, where $1Bq = 1\text{ disintegration/second (dps)}$.

Curie (Ci)

The old unit of radioactivity; $1Ci = 3.7 \times 10^{10}Bq$. Marie Curie coined the term radioactivity and discovered polonium and radium.

Radioactive Decay

The process where certain nuclides spontaneously emit radiation (alpha, beta, gamma rays) to reach a stable state.

Decay Constant ($\lambda$)

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

Half-life ($T_{1/2}$)

The amount of time required for the activity of a radioactive sample to decay to one half of its original value.

Alpha Decay

Occurs in heavy nuclides; resembles a Helium ($He$) element with a relative charge of $2$ and a mass of $4$.

Beta Decay

Involves negatron and positron decay with a relative charge of $-1$ and a mass of $0$.

Isomeric Transition

A decay mode that emits gamma ($\gamma$) rays and occurs only in elements in an excited state.

Internal Conversion (K-Conversion)

The removal of an electron within an atom by a gamma ($\gamma$) ray from the nucleus.

Electron Capture (K-Capture)

A process where the nucleus captures an electron from an orbital shell.

Auger Process

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

Electron Volt (eV)

The energy acquired by an electron accelerated through a potential difference of $1\text{ volt}$; $1eV = 1.6 \times 10^{-19}J$.

Photon Amplitude

One half the range from crest to valley over which the sine wave varies.

Photon Wavelength ($\lambda$)

The distance from one crest to another.

Photon Frequency ($f$)

The rate of rise and fall of a sine wave, measured in Hertz ($Hz$) or cycles/second.

Wave Equation

The mathematical relationship for electromagnetic radiation: c = f\text{\lambda}, where $c$ is the speed of light.

Inverse Square Law

States radiation intensity is inversely proportional to the square of the distance from the source.

Specific Ionization (SI)

The number of ion pairs formed per unit path length for a given type of radiation.

Linear Energy Transfer (LET)

The rate at which energy is transferred from ionizing radiation to soft tissue, expressed in $keV/μm$.

Bremsstrahlung

Often referred to as 'white x-rays'.

Characteristic X-rays

X-rays produced by the filling of a vacancy in an orbital shell.

Classical Scattering

Also known as Coherent, Thomson, or Rayleigh scattering; an incident photon excites an atom causing a change in direction without a change in wavelength or ionization.

Compton Interaction

A high-energy photon interaction where an outer-shell electron is ejected, resulting in ionization and scattered radiation; most hazardous to radiation workers.

Photoelectric Effect

Total absorption of an incident x-ray which ejects an inner-shell (K-shell) electron called a photoelectron; occurs with $75\%$ probability.

Pair Production

Occurs with x-rays above $1.022MeV$; the photon interacts with the nuclear force field to create a negatron and a positron, each with $0.511MeV$.

Photodisintegration

An interaction where a high-energy photon ($≥ 7-10MeV$) is absorbed by the nucleus, causing the emission of a nuclear fragment.

Conductors

Materials like copper and aluminum that allow the flow of electrons.

Insulators

Materials such as wood, glass, and rubber that inhibit the flow of electrons.

Superconductors

Materials like niobium and titanium that allow electron flow with no resistance.

Ohm's Law

States that current is directly proportional to potential difference and inversely proportional to resistance.

Electric Power

The rate of electric energy transfer, measured in watts ($W$); $P = IV = I^2R$. One watt equals one ampere multiplied by one volt ($W = AV$).

Tesla (T)

The SI unit of magnetic field strength; $1T = 10,000G$ (gauss).

Electric Generator

A device that converts mechanical energy into electrical energy based on Faraday's Law.

Electric Motor

A device that transforms electrical energy into mechanical energy.

Stator

Fixed electromagnets located outside the glass envelope of the x-ray tube.

Rotor

The part of the motor located inside the glass envelope of the x-ray tube that rotates due to induction.

Transformers

Devices that change the intensity of alternating voltage and current through mutual induction.

Hysteresis loss

Energy loss in a transformer resulting from the core material being continually magnetized and demagnetized by AC current.

Eddy Currents

Currents in a transformer core that oppose the magnetic field that induced them.

Autotransformer

A transformer with a single winding designed to supply precise voltage to the filament and high-voltage circuits.

Capacitor

A device used to store and release electricity temporarily; does not conduct electricity.

Potter-Bucky Tray

A device discovered in 1913 that holds the cassette and grid under the x-ray table.

Bucky slot cover

A cover with at least $0.25mm$ lead equivalence that protects the opening created when the Bucky tray is moved during fluoroscopy.

Line Compensator

A device that measures the incoming voltage and adjusts it to precisely $220V$.

Filament Circuit

A separate circuit that controls the tube current by regulating filament temperature, typically operating between $3A$ and $6A$.

Synchronous Timers

Timing mechanisms driven by a shaft at $60$ revolutions per second ($rps$); minimum exposure time is $1/60s$.

Electronic Timers

The most sophisticated and accurate x-ray timers, controlled by a microprocessor.

Spinning Top

A simple mechanical device used to check the accuracy of x-ray timers.

Rectifier

An electronic device (diode) that allows current to flow in only one direction, converting AC to DC.

Voltage Ripple

The amount of fluctuation in the voltage of the power to an x-ray machine; less ripple results in higher radiation quantity and quality.

Protective Housing

Lead-lined container that prevents x-ray leakage, isolates high voltages, and cools the tube; leakage must not exceed $100mR/hr$ at $1\text{ meter}$.

Expansion Gasket

A rubber diaphragm that expands and contracts with oil temperature changes, often linked to a micro switch to stop exposures if overheating occurs.

Focusing Cup

A negatively charged molybdenum or nickel cup that encases the filaments and focuses the electron cloud toward the anode.

Thermionic Emission

The process of boiling off electrons from a heated filament.

Thoriated Tungsten

The material used for filaments because of its high melting point ($3,410^∘C$) and high electron emission.

Anode Stem

A copper structure that attaches the rotating target to the rotor.

Rotating Target

An anode component made of tungsten with $5-10\%$ rhenium to increase thermal capacity and withstand heat.

Actual Focal Spot

The physical area of the focal track on the anode that is bombarded by electrons.

Effective Focal Spot

The area of the focal spot projected out of the tube toward the object being radiographed; reduced by the Line-Focus Principle.

Line-Focus Principle

The design concept where angling the anode results in a smaller effective focal spot compared to the actual focal spot.

Anode Heel Effect

An effect where radiation intensity is higher on the cathode side of the x-ray tube than on the anode side due to the line-focus principle.

Tungsten Vaporization

The most common cause of x-ray tube failure, where atoms coat the glass or metal envelope.

Radiographic Tube Rating Chart

A chart that presents the safe and unsafe technical factors (kVp, mA, time) for a specific x-ray tube.

Anode Cooling Chart

A chart showing the thermal capacity of an anode and the time required for it to dissipate heat units ($HU$).

Heat Units (HU) formula

Calculated as $HU = kVp \times mA \times \text{time (s)}$.