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Ch. 2 - Radiation Physics

Terms in this set (95)

Absorption
Refers to the total transfer of energy from the x-ray photon to the atoms of matter through which the x-ray beam passes. Absorption depends on the energy of the x-ray beam and the composition of the absorbing matter or tissues.
Alpha particles
A type of particulate radiation emitted from the nuclei of heavy metals and exist as two protons and 2 neutrons, without electrons. Positively charged
Aluminum disks
Disks or sheets of 0.5 thick aluminum placed in the path of the x-ray beam - filter out the non-penetrating, longer wavelength x-rays.
Amperage
The number of electrons moving through a conductor; the strength of an emulsion.
Ampere (A)The measurement of current.
The unit of measure used to describe the number of electrons passing through a conductor (electrical current strength); the intensity of an electric current produced by 1 volt acting through a resistance of 1 ohm.
Anode
Positive electrode, consists of wafer-thin tungsten plate embedded in a solid copper rod. Purpose of the anode is to convert electrons into x-ray photons.
Atom
The fundamental unit of matter is the atom. all matter is composed of atoms, or tiny invisible particles. The atom consists of a central nucleus and orbiting electrons
Atom, neutral
The atom consists of a central nucleus and orbiting electrons
An atom contains a maximum of seven shells. Atoms have a neutral charge unless altered in some way. Contains an equal number of protons (positive charges) and electrons (negative charges).
Atomic number
The total number of protons inside the nucleus equals the number of electrons outside the nucleus and determines the atomic number of the atom.
Atomic weight
The total number of protons and neutrons in the nucleus of an atom determines its mass number or atomic weight.
Autotransformer
Serves as a voltage compensator that corrects for minor fluctuations in the current.
Beta Particles
Are fast-moving electrons emitted from the nucleus of radioactive atoms.
Binding energy
Electrons are maintained in their orbits by the electrostatic force, or attraction, between the positive nucleus and the negative electrons. Also known as binding energy, or binding force, of an electron. The binding energy is determined by the distance between the nucleus and the orbiting electron and is different for each shell. The strongest binding energy is found in the closest to the nucleus in the K shell.
Bremsstrahulung - Braking radiation
Speeding electrons slow down because of their interactions with the tungsten target in the anode. Many electrons that interact with the tungsten atoms undergo not one but many interactions within the target. Known as general radiation, or braking radiation - bremsstrahulung.
Cathode
Cathode, or negative electrode, consists of a tungsten wire filaments in a cup-shaped holder made of molybdunum. Supplies the electrons necessary to generate x-rays. Electrons produced in the negative cathode are accelerated toward the positive anode.
Cathode ray
A stream of high-speed electrons that originates from the cathode in an e-ray tube.
Circuit
Is a path of electrical current
Two electrical circuits are used in the production of x-rays
1. Low-voltage or filament circuit
2.High-voltage circuit.
Circuit, filament
Uses 3-5 volts, regulates the flow of electrical current to the filament of the x-ray tube and is controlled by the milliampere setting - also known as the low-voltage circuit.
Circuit, high-voltage
Uses 65,000-100,000 volts, provides the high voltage required to accelerate electrons and to generate x-rays in the x-ray tube, and is controlled by the kilovoltage settings.
Coherent scatter
One of the interactions of x-radiation with matter in which the path of a low-energy x-ray photon interacts with an out-shell electron. No change in the atom occurs, and an x-ray photon of scattered radiation is produced - also known as unmodified scatter.
Compton electron
An outer-shell electron that is ejected from its orbit during Compton scatter; this electron carries a negative charge.
Compton scatter
One of the interactions of x-radiation with matter in which the x-ray photon collides with a loosely bound, outer-shell electron and gives up part of its energy to eject the electron from its orbit. The x-ray photon loses energy and continues in a different direction at a lower energy level.
Control panel
The control panel of the dental x-ray machine contains: an indicator light, and exposure button and indicator light, and control devices - time, kilovoltage, & milliamperage selectors - to regulate the x-ray beam.
Copper stem
A portion of the anode that dissipates heat away from the tungsten target.
Current, alternating (AC)
Describes an electrical current in which the electrons flow in two, opposite directions.
Current, direct (DC)
Electrical current is termed direct current when electrons flow in one direction through the conductor.
Electrical current
The flow of electrons through a conductor; an electrical current is used to produce x-rays.
Electricity
Electrical current used as a source of power; the energy used to make x-rays.
Electromagnetic spectrum
Electromagnetic radiations are arranged according to their energies in what is termed the electromagnetic spectrum. All energies of the electromagnetic spectrum share common characteristics. Can be classified as ionizing or non-ionizing
Electron
Electrons are tiny, negatively charged particles that have very little mass; an electron weighs approximately 1/1800 as much as a proton or neutron. They are found outside of the nucleus in the atom.
Electron volt (eV)
The unit of measurement for the binding energies of orbital electrons (eV) or kilo electron volts (keV) - One kilo electron volt equals 1000 electron volts.
Electrostatic force
Electrons are maintained in their orbits by the electrostatic force, or attraction, between the positive nucleus and the negative electrons. Also known as binding energy, or binding force, of an electron.
Element
Elements are substances made up of only one type of atom
Energy
When matter is altered, energy results
Extension arm
Wall-mounted extension arm suspends the x-ray tubehead and houses the electrical wires that extend from the control panel to the tubehead allowing for movement and positioning of tubehead.
Frequency
Refers to the number of wavelengths that pass a given point in a certain amount of time. The amount of energy an electromagnetic radiation possesses depends on the wavelength and frequency. Diagnostic radiography uses the high-frequency, shorter waves in the electromagnetic spectrum; x-rays used in dentistry have a wavelength of 0.1 or 0.00000000001 m.
Insulating oil
Oil that surrounds the x-ray tube and transformers inside the tubehead - prevents overheating by absorbing the heat created by the production of x-rays.
Ion
An atom that gains or loses an electron and becomes electrically unbalanced is known as an ion.
Ion pair
When an electron is removed from an atom in the ionization process, an ion pair results. The atom becomes the positive ion, and the ejected electron becomes the negative ion.
Ionization
The production of ions; the process of converting an atom into an ion, resulting in the formation of a positive atom and dislodged negative electron.
Kilo electron volt (keV)
Binding energies of orbital electrons are measured in electron volts (eV) or kilo electron volts (keV) - One kilo electron volt equals 1000 electron volts.
Kilovolt (kV)
Voltage is measured in volts (V) or kilovolts (kV)
Kilovoltage peak (kVp)
The voltage of the x-ray tube current, or the current passing from the cathode to the anode, is controlled by the kilovoltage peak (kVp) adjustment on the control panel.
Kinetic energy
The energy of motion
Lead collimator
A lead diaphragm or tubular device used to restrict the size and shape of the x-ray beam.
Leaded-glass housing
Leaded-glass vacuum tube that prevents x-rays from escaping in all directions. The x-ray beam exits through a leaded-glass tube window. X-ray beam to exit the tube and directs the x-ray beam toward the aluminum disks, lead collimator, and PID.
Mass number
The number of protons and neutrons in the nucleus of an atom determines its mass number or atomic weight.
Matter
Matter is anything that occupies space and has mass
Metal housing
Metal body of the tubehead that surrounds the x-ray tube and transformers and is filled with oil - protects the x-ray tube and grounds the high-voltage components.
Milliamperage (mA)
In radiography, the quantity, or number, of x-rays emitted from the tubehead; measured in milliamperes.
Milliampere (mA)
1/1000 of an ampere; a unit of measurement used to describe the intensity of an electrical current.
Molecule
A molecule can be defined as two or more atoms joined by chemical bonds, or the smallest amount of a substance that possesses its characteristic properties.
Molecules are formed in one of two ways. By the transfer of electrons or by the sharing of electrons between the outermost shells of atoms
Molybdenum cup
Focuses the electrons into a narrow beam and directs the beam across the tube toward the tungsten target of the anode. Found in the Cathode
Nanometer
Wavelength is measured in nanometers - nm; one billionth of a meter.
Neutron
An electrically neutral or uncharged particle.
Nucleon
Part of an atomic nucleus - e.g., protons, neutrons
Nucleus
The nucleus, or dense core of the atom, is composed of particles known as protons and neutrons, also known as nucleons
Orbit
The arrangement of the electrons and neutrons in an atom resembles that of a miniature solar system. Just as the planets revolve around the sun, electrons travel around the nucleus in well-defined paths known as orbits or shells.
Periodic table of the elements
Atoms are arranged in the ascending order of atomic number on a chart known as the periodic table of the elements
Photoelectric effect
One of the interactions of x-radiation with matter; the x-ray photon collides with a tightly bound, inner-shell electron and gives up all its energy to eject the electron from its orbit. All the energy of the photon is absorbed by the displaced electron in the form of kinetic energy.
Photon
A bundle of energy with no mass or weight that travels as a wave at the speed of light and moves through space in a straight line.
Position-indicating device (PID)
Open-ended, lead-lined cylinder that extends from the opening of the metal housing of the tubehead - aims and shapes the x-ray beam. PID is sometimes referred to as the cone.
Primary beam
The penetrating x-ray beam produced at the target of the anode and that exits the tubehead - also known as the primary beam or useful beam.
Proton
A positively charged particle with a mass of one.
Quanta
The particle concept characterizes electromagnetic radiations as discrete bundles of energy called photons, or quants. Photons are bundles of energy with no mass or weight that travel as waves at the speed of light and move through space in a straight line, "carrying the energy" of electromagnetic radiation.
Radiation
A form of energy carried by waves or a stream of particles.
Radiation, braking
A form of radiation that occurs when speeding electrons slow down because of their interactions with the tungsten target in the anode - also known as bremsstrahlung or braking radiation.
Radiation, characteristic
Produced when a high-speed electron dislodges an inner-shell electron from the tungsten atom and causes ionization of the atom.
Radiation, electromagnetic
Electromagnetic radiation can be defined as the propagation of wavelike energy (without mass) through space or matter. The energy propagated is accompanied by oscillating electric and magnetic fields positioned at right angles to one another, thus the term electromagnetic.
Radiation, general
SA form of radiation that occurs when speeding electrons slow down because of their interactions with the tungsten target in the anode - also know as bremsstrahlung or braking radiation.
Radiation, ionizing
Radiation that is capable of producing ions by removing or adding an electron to an atom. Classified into two groups: 1. Particulate radiation & 2. Electromagnetic radiation
Radiation, particulate
Particulate radiations are tiny particles of matter that possess mass and travel in straight lines and a high speeds. They transmit kinetic energy by means of their extremely fast-moving, small masses.
Four Types:
1. Electrons:beta particles & cathode rays
2. Alpha particles
3. Protons
4. Neutrons
Radiation, primary
The penetrating x-ray beam that is produced at the target of the anode and that exits the tubehead. Primary beam
Radiation, scatter
A form of secondary radiation and is the result of an x-ray that has been deflected from its path by the interaction with matter. Detrimental to both the patient and the radiographer.
Radiation, secondary
Refers to x-radiation that is created when the primary beam interacts with matter. Dental matter: soft tissues of the head, bones of the skull, and teeth. Secondary radiation is less penetrating than primary radiation.
Radioactivity
Radioactivity can be defined as the process by which certain unstable atoms or elements undergo spontaneous disintegration, or decay, in an effort to attain a more balanced nuclear state. A substance is considered radioactive if it gives off energy in the form of particles or rays as a result of the disintegration of atomic nuclei.
Recoil electron
An outer-shell electron that is ejected from its orbit during Compton scatter; this electron carries a negative charge.
Rectification
Rectification is the conversion of AC to DC. The dental x-ray tube acts as a self-rectifier in that it changes AC into DC while producing x-rays
Shell
The arrangement of the electrons and neutrons in an atom resembles that of a miniature solar system. Just as the planets revolve around the sun, electrons travel around the nucleus in well-defined paths known as orbits or shells.
Thermionic emission
The release of electrons from the tungsten filament when the electrical current passes through it and heats the filament.
Transformer
Device that is used to either increase or decrease the voltage in an electrical circuit. Transformers alter the voltage of incoming electrical current and then route the electrical energy to the x-ray tube.
Transformer, step-down
In dental radiography, step-down transformer is used to decrease the voltage from the incoming 110- or 220- line voltage to the 3-5 volts used by the filament circuit. When you turn the machine on is makes a Direct Current (DC) & produces an electron cloud.
Transformer, step-up
In dental radiography, a step-up transformer is used to increase the voltage from the incoming 110- or 220-line voltage to the 65,000 -100,000 volts used by the high-voltage circuit. When you press the exposure button energy travels from the cathode to the anode, thus producing the x-radiation.
Tubehead
A tightly sealed, heavy metal housing that contains the x-ray tube; includes the metal housing, insulating oil, tubehead seal, x-ray tube, transformers, aluminum discs, lead collimator, and posisiton-indicating device (PID); contains a filament used to produce electrons and a target used to produce x-rays.
Tubehead seal
The aluminum or leaded-glass covering of the tubehead that permits the exit of x-rays from the tubehead; seals the oil in the tubehead and filter the x-ray beam.
Tungsten filament
A portion of the cathode in the x-ray tube; a coiled wire of tungsten that produces electrons when heated.
Tungsten target
A portion of the anode in the x-ray tube; which serves as a focal spot and converts bombarding electrons into x-ray photons.
Unmodified scatter
One of the interactions of x-radiation with matter in which the path of a low-energy x-ray photon interacts with an out-shell electron. No change in the atom occurs, and an x-ray photon of scattered radiation is produced - also known as unmodified scatter.
Useful beam
The penetrating x-ray beam that is produced at the target of the anode and that exits the tubehead. Primary beam
Velocity
In dental radiography; refers to the speed of a wave. All electromagnetic radiations travel as waves or a continuous sequence of crests at the speed of light - 3x108 meters per second or 186,000 miles per second in a vacuum.
Volt (V)
Voltage is measured in volts (V) or kilovolts (kV)
Voltage
In dental radiography, measurement of force that refers to the potential difference between two electrical charges.
Wavelength
Is the distance between the crest of one wave and the crest of the next. Wavelength determines the energy and penetrating power of the radiation; the shorter the distance between the crests, the shorter is the wavelength and the higher is the energy and ability to penetrate matter. Wavelength is measured in nanometers - nm; one billionth of a meter.
X-rays
A beam of energy that has the power to penetrate substances and record image shadows on photographic film or digital sensors.
X-ray tube
The heart of the x-ray generating system; it is critical to the production of x-rays. It is a glass vacuum tube from which all the air has been removed. Component parts: leaded-glass housing, negative cathode, and positive anode
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