LRA 211 Week 1 Key Terms

Atom

The basic building block of matter, described as having three fundamental components: electrons, neutrons, and protons.

Atomic Mass Number

The number of protons and neutrons an atom has in its nucleus.

Atomic Number

The number of protons in the nucleus of an atom, which also indicates the number of electrons in a stable atom.

Binding Energy

Refers to the strong nuclear force that creates a very strong attraction in the nucleus, overcoming the natural tendency for like charges to repel.

Compound

A molecule that contains at least two different elements.

Covalent Bond

A bond based on two atoms sharing electrons that then orbit both nuclei, completing the outermost shell of each.

Electron

A subatomic particle with one unit of negative electrical charge and a mass significantly less than that of protons or neutrons, orbiting the nucleus at high velocities.

Electron Shell

Defined energy levels at different distances from the nucleus, where electrons orbit three dimensionally around the nucleus.

Element

The simplest form of substances that compose matter, made up of one unique type of atom with an unchanging number of protons.

Ionic Bond

A bond based on the attraction between atoms of opposite charge, occurring when one atom gives up an electron (becoming a cation with a net positive charge) and another atom takes on that electron (becoming an anion with a net negative charge).

Molecule

Formed when two or more atoms join together chemically.

Neutron

A component of the nucleus with no electrical charge and a specific mass, contributing to the majority of an atom's mass along with protons.

Nucleus

The central part of an atom, made up of protons and neutrons (collectively called nucleons) and is the core around which electrons orbit.

Proton

A component of the nucleus with one unit of positive electrical charge and a specific mass, contributing to the atomic number of an atom.

Alpha Particles

Physical particles originating from radioactive atoms, composed of two protons and two neutrons (the same makeup of the nucleus of a helium atom), with a net positive charge.

Beta Particles

Electrons emitted from an unstable nucleus; they do not originate in an electron shell.

Electromagnetic Radiation

An electric and magnetic disturbance traveling through space at the speed of light, carrying energy in waves. It varies only in energy, wavelength, and frequency but has no mass.

Electromagnetic Spectrum

A classification of electromagnetic radiations according to their energy, wavelength, and frequency, ranging from radiowaves to gamma rays.

Gamma Rays

High-energy electromagnetic radiation that exhibits both wave and particle characteristics, capable of ionizing matter.

Hertz (Hz)

The unit of frequency in the International System of Units (SI), equivalent to one cycle per second.

Infrared Light

Low-energy electromagnetic radiation just above microwaves in the electromagnetic spectrum, used for communication between electronic devices. It does not ionize atoms.

Inverse Square Law

The principle that the intensity of electromagnetic radiation diminishes by the square of the distance from the source, applicable to light luminosity and radiation intensity.

Ionization

The process by which a photon with sufficient energy removes an electron from the orbit of an atom, creating an ion pair.

Microwaves

Electromagnetic waves used for transmitting cell phone signals and heating food, with frequencies around 2500 MHz. They can cause heating of tissues but do not ionize atoms.

Particulate Radiation

Radiation consisting of physical particles, such as alpha and beta particles, that originate from radioactive atoms and have the ability to ionize matter.

Photon

A packet of electromagnetic energy with properties of both waves and particles, the energy of which is determined by the frequency and Planck’s constant.

Planck’s Constant

A fundamental constant used to calculate the energy of photons, equal to 6.626 × 10^−34 joule seconds (J s).

Radioactivity

The process by which an atom with excess energy in its nucleus emits particles and energy to regain stability, known as radioactive decay.

Radiowaves

Electromagnetic waves used for broadcasting and in MRI, characterized by their long wavelengths and low frequencies. They do not ionize atoms.

Ultraviolet Light

Part of the electromagnetic spectrum with energies approaching those of x-rays and gamma rays, used in tanning beds and capable of causing skin cancer but does not ionize atoms.

Visible Light

The portion of the electromagnetic spectrum perceivable by the human eye, consisting of all colors from violet to red. It does not ionize atoms.

Wavelength

The distance from the peak of one wave to the peak of the next in the electromagnetic spectrum, inversely related to frequency and typically expressed in meters.

X-rays

High-energy electromagnetic radiation used in medical imaging and radiation therapy, capable of ionizing matter.

Actual Focal Spot

The area on the anode that is actually bombarded by the electrons from the cathode.

Anode

The positive end of the x-ray tube that serves as the target for the electron interactions necessary for x-ray production.

Anode Heel Effect

A phenomenon where the intensity of the x-ray beam is less on the anode side of the x-ray tube due to the absorption of x-rays by the "heel" of the anode target.

Cathode

The negative end of the x-ray tube that provides the source of electrons for x-ray production.

Effective Focal Spot

The apparent size of the X-ray source as viewed from the position of the image receptor (like a film or detector). It is always smaller than the actual focal spot due to the angle of the anode (target).

Filament

A coil of wire within the cathode of the x-ray tube that emits electrons when heated.

Focusing Cup

A part of the cathode designed to direct the electrons emitted from the filament toward the anode target.

Heat Units (HUs)

A measure of the amount of heat generated during an x-ray exposure, calculated with the formula kVp × mA × s × correction factor, which varies by the type of generator used.

Induction Motor

A type of motor used to rotate the anode within the x-ray tube.

Leakage Radiation

Radiation that escapes from the protective housing of the x-ray tube, other than through the designated window or port for clinical use.

Line-Focus Principle

A design principle of the x-ray tube where the anode target is angled to create a large actual focal spot for heat dissipation and a small effective focal spot for improved image resolution.

Protective Housing

The enclosure that contains the x-ray tube, providing mechanical support, electrical insulation, and thermal management.

Rotor

Part of the induction motor within the x-ray tube that rotates the anode.

Space Charge

A cloud of electrons emitted from the cathode filament in the x-ray tube.

Space-Charge Effect

A phenomenon that limits the emission of additional electrons from the cathode as the space charge increases, affecting the efficiency of x-ray production.

Stator

The part of the induction motor located outside the x-ray tube's vacuum that generates a rotating magnetic field to drive the rotor and thus spin the anode.

Target Window

The area in the x-ray tube envelope designed to allow the exit of x-rays with minimal absorption.

Thermionic Emission

The release of electrons from the cathode filament when it is heated to incandescence, creating a cloud of electrons that can be accelerated towards the anode to produce x-rays.

The source of x-ray emission within an x-ray tube

Actual Focal Spot

Electron interactions within the x-ray tube anode primarily create:

Heat

The area of the x-ray beam projected towards the patient is described as:

Effective focal spot

The Line-Focus Principle describes the geometric relationship between these factors within an x-ray tube:

Anode angle & effective focal spot size

Which anode angle with the same size actual focal spot can create a radiographic image demonstrating the highest spacial resolution?

6 degrees

Which anode angle with the same size actual focal spot can tolerate the highest technical setting without overheating?

20 degrees

When comparing a small anode angle to a large anode angle, a small anode angle with the same size focal spot will result in what?

Increased spatial resolution & decreased anode heat capacity

Utilizing an x-ray tube with a large anode angle, compared to a tube with a small angle and the same size actual focal spot will result in

Decreased spatial resolution and increased anode heat capacity

A radiographer has the choice of multiple radiographic systems, each using a different anode angle. Which system should be used if maximum spatial resolution is desired?

7 degrees

A radiographer has the choice of multiple radiographic systems, each using a different actual focal spot size. Which system should be used if maximum heat dissipation is required?

2.4 cm

Which three imaging modalities use an x-ray tube?

Mammography

Fluoroscopy

Computed tomography (CT)

Which component of the x-ray tube is the source of free electrons?

Cathode

What component of the x-ray tube is the source of x-rays?

Anode

The term “space charge” within the x-ray tube refers to:

Free electrons

The space charge affect limits the functional milliamperage (mA) of the x-ray tube to approximately:

1,000 mA

What is the principle advantage of using the large filament within a dual focus x-ray tube?

Increased heat capacity

Which of the following situations will require the use of the large filament within a dual focus x-ray tube?

Abdominal imaging on a bariatric patient

The anode Hill effect is defined as a variation in which of the following

Beam quantity across the x-ray field

As a result of the anode heel affect the antinode side of the x-ray field demonstrates

Lower intensity

The use of an x-ray tube with a large anode angle results in which two of the following

Increased focal spot size and increased heat capacity

What is the antinode heel effect caused by?

X-ray absorption within the anode

Directing the anode side of the x-ray field towards the toes during an anteroposterior (AP) projection of the foot results in

More uniform receptor exposure

The use of an x-ray tube with a small anode angle results in

Decreased focal spot size and decreased heat capacity

Which of the following exposure modifications will increase the antinode heal effect

Decreased Source to image distance (SID)

When using a 14 × 17 - inch exposure field, the intensity of the central Ray measures 100 milligrays (mGy). what is the approximate intensity of the beam within the cat outside of the x-ray field?

120 mGy

What is a potentially negative consequence of an increased anode angle?

Increased effective focal spot

What occurs when the anode angle decreases?

Effective focal spot size decrease decreases, and the heel effect increase increases