Physics Flashcards
Matter
Anything that occupies space and has mass.
Atoms
All matter is composed of fundamental building blocks
Mass
is the quantity of matter as described by its energy equivalence.
Weight
Mass and weight may be considered to be the same but that in the strictest sense, they are not the same. Mass is actually described by its energy equivalence, weight is the force exerted on a body under the influence of gravity.
Mass
measured in kilograms
Kilo
stands for 1000
Building blocks of matter
atoms and molecules
Energy
is the ability to do work
Potential Energy
the ability to do work by virtue of position.
Kinetic energy
is the energy of motion
Chemical energy
energy released by a chemical reaction
Electrical energy
represents the work that can be done when an electron moves through an electron potential difference (voltage).
Thermal energy
energy of motion at the molecular level
Nuclear energy
energy that is contained within the nucleus of an atom.
Electromagnetic energy
x-rays, radio waves, microwaves; and ultraviolet, infrared, and visible light.
Mass-Energy (Einstein)
E=mc^2
Where E is energy, m is mass, and c is the velocity (speed) of electromagnetic radiation (light) in a vacuum
Radiation
energy emitted and transferred through space
Electromagnetic radiation
visible light, a form of electromagnetic energy, is radiated by the sun.
Electromagnetic energy
usually referred to as electromagnetic radiation or, simply, radiation.
Exposed or Irradiated
Matter that intercepts radiation and absorbs part or all of it.
Ionizing radiation
is a special type of radiation that includes x-rays.
Ionization
is the removal of an electron from an atom
Ion pair
Two opppositely charged particles
1% voltage ripple
High frequency generators that higher x-ray quantity and quality
100% voltage ripple
Single phase power in which the voltage varies from zero to its maximum value
14% ripple
Three-phase, six pulse power whose voltage supplied to the x-ray tube never falls below 86% of peak value.
4% voltage ripple
Three phase, 12 pulse power whose voltage supplied to the x-ray tube never falls below 96% of peak value.
Abrasion layer
Protective covering of gelatin that encloses an emulsion.
Absorbed dose
Energy transferred from ionizing radiation per unit mass of irradiated material; expressed in rad (100 erg/g) or gray (1 J/kg).
Absorption blur
Characteristic of a subject that affects subject contrast
Absorption
Transfer of energy from an electromagnetic field to matter; removal of x-rays from a beam via the photoelectric effect.
Acceleration
Rate of change of velocity over time
Acceleration of gravity
constant rate at which objects falling to the Earth accelerate.
Acetic acid
chemical used in the stop bath
Activator
chemical, usually acetic acid in the fixer and sodium carbonate in the developer, used to neutralize the developer and swell the gelatin.
Active memory
data can be stored or accessed at random from anywhere in main memory in approximately equal amounts of time, regardless of where the data are located.
Actual focal spot size
Area on the anode target that is exposed to electrons from the tube current.
Acute radiation syndrom
Radiation sickness that occurs in humans after whole body doses of 1 Gy (100 rad) or more of ionizing radiation delivered over a short time.
Adhesive layer
Protective covering of gelatin that encloses the emulsion
Aerial oxidation
Oxidation that occurs when air is introduced into the developer after it is mixed, handled, and stored.
Afterflow
phosphorescence in an intensifying screen.
Air gap technique
Practice of moving the image receptor 10 to 15 cm from the patient so that fewer scattered x-rays interact with the image receptor, thereby enhancing contrast.
ALARA
As low as reasonably achievable
Algorithm
Computer adapted mathematical calculation applied to raw data during image reconstruction
Alpha particle
Particulate form of ionizing radiation that consists of two protons and two neutrons; nucleus of helium emitted from the nucleus of a radioactive atom.
Alternating current (AC)
Oscillation of electricity in both directions within a conductor.
Amber filter
Filter that transmits light with wavelengths longer than 550 nm, which is above the spectral response of blue sensitive film
Ammeter
Device that measures current
Ampere (A)
SI unit of electric charge: 1 A = 1 C/s
Amplitude
Width of a waveform
Anabolism
Process of synthesizing smaller molecules into a larger macromolecule.
Anaphase
Third phase of mitosis, during which chromatids repel one another and migrate along the mitotic spindle to opposite sides of the cell.
Anatomically programmed radiography (APR)
Technique by which graphics on the console guide the technologist in selection of a desired kVp and mAs.
Anode
Positively charged side of an x-ray tube that contains the target.
Anthropomorphic
Human characteristics
Aperture diaphragm
Simple beam restricting device that attaches a lead-lined metal diaphragm to the head of the x-ray tube.
Aperture
circular opening for the patient in the gantry of a computed tomographic or magnetic resonance imaging system. B) fixed collimation of a diagnostic x-ray tube, as in an aperture diaphragm.
Archival quality
Attribute that refers to the fact that the image does not deteriorate with age but remains in its original state.
Area beam
X-ray beam pattern that usually is shaped like a square or a rectangle, and that is used in conventional radiography and fluoroscopy.
Array processor
Part of a computer that handles raw data and performs the mathematical calculations necessary to reconstruct a digital image.
Artifact
Unintended optical density on a radiograph or another film type image receptor.
Asthenic
Referring to the body habitus of a patient who is small and frail.
Atom
Smallest particle of an element that cannot be divided or broken by chemical means.
Atomic mass number
Number of protons plus number of neutrons in the nucleus.
Atomic mass unit
Mass of a neutral atom of an element, expressed as one twelfth the mass of carbon, which has an assigned value of 12.
Atomic mass
Relative mass of a specific isotope of an element.
Atomic number (Z)
Number of protons in the nucleus.
Atrophy
Shrinking of a tissue or organ.
Attenuation
Reduction in radiation intensity that results from absorption and scattering.
Automatic brightness control (ABC)
Feature on a fluoroscope that allows the radiologist to select an image brightness level that is subsequently maintained automatically by varying the kVp, the mAs, or both.
Automatic exposure control (AEC)
Feature that determines radiation exposure during radiography in most x-ray imaging systems.
Autotransformer law
Principle stating that the voltage received and the voltage provided are directly related to the number of turns of the transformer enclosed by the respective connections.
Autotransformer
Transformer located in the operating console that controls the kVp; it consists of one winding of wire and varies voltage and current by self induction.
Average gradient
Measure of radiographic contrast
Axial tomography
Conventional tomography in which the plane of the image is parallel to the long axis of the body; this results in sagittal and coronal images.
Axial
perpendicular to the long axis of the body
Backscatter radiation
X-rays that have interacted with an object and are deflected backward.
Bandpass
Number of times per second that the electron beam can be modulated.
Base density
Optical density inherent in the base of the film.
Base plus fog
Average density from an unexposed area of the strips.
Base
Area that serves as a mechanical support for the active phosphor layer in a radiographic intensifying screen.
Beam axis
Central line that represents maximal ultrasound or xray intensity
Beam penetrability
Ability of an xray beam to penetrate tissue.
Beam restrictor
Device that restricts the size of the xray field to only the anatomical structure of interest.
Beam limiting device
Device that provides a means of restricting the size of an x-ray field.
Becquerrel (Bq)
Special name for the SI units of radioactivity. One becquerel is equal to disintegration per second.
Beta particle
Ionizing radiation with characteristics of an electron; emitted from the nucleus of a radioactive atom.
Binary number system
Number system with only two digits, 0 and 1.
Bipolar
Magnet that has two poles
Bit depth
Number of bits used to reproduce image gray levels (eg., 8 bits=2^8=256 gray levels)
Bit
smallest unit of measure in computer storage capacity
Body habitus
General size and shape of a patient
Brachytherapy
Radiation oncology in which the source of tradition is on or in the body.
Bremsstrahlung x-ray
X-rays that results from interaction of the projectile electron with a target nucleus; braking radiation.
Brightness gain
Ability of the image intensifier to increase the illumination level of the image.
Bucky factor
Ratio of incident radiation to transmitted radiation through a grid; ratio of patient dose with and without a grid.
Bucky slot cover
Protective cover that automatically shields the Bucky slot opening during fluoroscopic examinations when the Bucky tray is at the foot of the table.
Buffer
Acetate added to the fixer to maintain a constant pH
Buffering agent
Alkali compound in the developer that enhances the action of the developing agent by controlling the concentration of hydrogen ions.
Byte
Group of eight bits; represents one character or digit.
Calipers
Instrument with two bent or curved legs used for measuring the thickness of a solid.
Calorie
Energy necessary to raise the temperature of 1 g of water by 1 celcius
C-arm fluoroscope
Portable device for fluoroscopy. The opposite ends of the C-shaped support arm hold the image intensifier and the xray tube.
Cassette
Rigid holder the contains the film and screens.
Cassette loaded spot film
conventional method of capturing images with image intensified fluoroscopes.
Catabolism
process that creates energy for a cell by breaking down molecular nutrients that are brought to and diffused through the cell membrane.
Cathode ray tube
Electron beam tube designed for a two dimensional display of signals
Cathode rays
Stream of electrons
Cathode
negative side of the x-ray tube; contains the filament and the focusing cup
Cell cloning
Process by which normal cells produce a visible colony in a short time.
Cell cycle time
Average time from one mitosis to another
Cell theory
Principle that all plants and animals contain cells as their basic functional units.
Cell
Basic unit of all living matter.
Central Axis x ray beam
X-ray beam composed of x-rays that travel along the center of the useful x-ray beam.
Central processing unit
Processing hardware in large computers
Central ray
Center of the xray beam that interacts with the image receptor
Centrifugal force
force that keeps an electron in orbit
Characteristic Curve
Graph of optical density versus log relative response; H&D curve.
Characteristic x-ray
X-ray released as a result of the photoelectric effect; its discrete energies are determined by the respective electron biding energy.
Charge coupled device
Solid state device that converts visible light photons to electrons.
Chemical Energy
Energy released by a chemical reaction
chemical fog
Artifact produced by chemical contamination of the developer
Chemical symbol
Alphabetic abbreviation for an element.
Chip
Tiny piece of semiconductor material
Classical scattering
Scattering of x-rays with no loss of energy. Also called coherent, Rayleigh, or thompson scattering.
Clearing agent
A chemical, usually ammonium thiosulfate, that is added to the fixer to remove undeveloped silver bromine from the emulsion.
Collimation
Restriction of the useful x-ray beam to reduce patient size and shape.
Commutator
Device that acts like a switch, converting an alternating current generator to a direct current generator.
Compensating filter
Material inserted between an x-ray source and a patient to shape the intensity of the x-ray beam. An x-ray beam filter is designed to make the remnant beam more uniform in intensity.
Compression device
Device that maintains close screen film contact when the cassette is closed and latched.
Compression
The act of flattening soft tissue to improve optical density.
Compton effect
Scattering of x-rays that results in ionization and loss of energy.
Compton scattering
Interaction between an x-ray and a loosely bound outer-shell electron that results in ionization and x-ray scattering.
Computed Radiography
Radiographic technique that uses a photostimulable phosphor as the image receptor and an area beam.
Computed tomography
Creation of a cross sectional tomographic section of the body with a rotating fan beam, a detector array, and computed reconstruction.
Computed tomography dose index
Radiation dose in a single slice over a 10 cm length so that dose delivered beyond the selected slice thickness is included.
Computer aided detection
Use of a highly complex pattern recognition
Conduction
Transfer of heat by molecular agitation
Conductor
Material that allows heat or electric current to flow
Cone cutting
Misalignment of cones that causes one side of the radiograph to not be exposed because the edge of the cone may interfere with the x-ray beam.
Cone
Circular metal tube that attaches to x-ray tube housing to limit the beam size and shape.
Cones and Cylinders
Modifications of the aperture diaphragm.
Connective tissue
Tissue that binds tissue and organs together
Contrast Agent
Compound used as an aid for imaging internal organs with x-rays.
Contrast improvement factor
Ratio of radiographic contrast with a grid to that without a grid.
Contrast Index
Difference between the step with an average optical density closest to 2.2 and the step with an average optical density closest to, but not less than, 0.5.
Contrast medium
Agent that enhances differences between anatomical structures.
Contrast resolution
Ability to distinguish between and to image similar tissues.
Contrast
Degree of difference between the light and dark areas of a radiograph.
Convection
Transfer of heat by the movement of hot matter to a colder place.
Conversion efficiency
Rate at which x-ray energy is transformed into light in an intensifying screen.
Conversion factor
Ratio of illumination intensity at the output phosphor to radiation intensity incident on the input phosphor.
Coolidge tube
Type of vacuum tube is use today that allows x-ray intensity and energy to be selected separately and accurately.
Cosmic rays
Particulate and electromagnetic radiation emitted by the sun and the stars.
Coulomb
SI unit of electric charge
Coupling
Joining of magnetic fields produced by the primary and secondary coils.
Covalent bond
Chemical union between atoms formed by sharing one or more pairs of electrons.
Covering power
The more efficient use of silver in an emulsion to produce the same optical density per unit exposure.
Crookes tube
Forerunner of modern fluorescent, neon, and x-ray tubes.
Crossed grid
Grid on which lead strips run parallel to the long and short axes.
Crossover rack
Device in an automatic processor that transports film from one tank to the next.
Cytoplasm
Protoplasm that exists outside the cell’s nucleus
Cytosineose
Nitrogenous organic base that attaches to a deoxyribose molecule.
Decimal system
System of numbers based on multiples of ten
Densitometer
Instrument that measures the optical density of exposed film.
Density difference
The difference between the step with an average optical density closest to 2.2 and the step with an average optical density closest to, but not less than, 0.5.
Detail
Degree of sharpness of structural lines on a radiograph.
Detective quantum efficiency
Percentage of x-rays absorbed by the image receptor.
Detector array
Group of detectors and the interspace material used to separate them; the image receptor in computed tomography.
Developing agent
A chemical, usually phenidone, hydroquinone, or Metol that reduces exposed silver ions to atomic silver.
Developing
Stage of processing during which the latent image is converted to a manifest image.
Development fogat enables imaging systems from different manu
Artifact that results from reduction of crystals that had not been exposed to metallic silver caused by the lack of a restrainer.
Diaphragm
Device that restricts an x-ray beam to a fixed size.
DICOM
Digital Imging and Communications in Medicine—Standard that enables imaging systems from different manufacturers to communicate.
Differential absorption
Different degrees of absorption in different tissues that result in image contrast and formation of the xray image.
Dimensional stability
Property that allows the base of radiographic film to maintain its size and shape during use and processing, so it does not contribute to image distortion.
Diode
Vacuum tube with two electrodes–a cathode and an anode.
Dipolar
Referring to a molecule with areas of opposing electric charge.
Direct current
flow of electricity in only one direction within a conductor.
Direct effect
Effect of radiation that occurs when ionizing radiation interacts directly with a particularly radiosensitive molecule.
Direct current motor
Electric motor in which many turns of wire are used for the current loop and many bar magnets are used to create the external magnetic field.
Direct exposure film
film used without intensifying screens.
Distortion
Unequal magnification of different portions of the same object.
Dose equivalent
Radiation quantity that is used for radiation protection and that expresses dose on a common scale for all radiation. Expressed in rem or sievert.
Dose length product
Product of computed tomography dose index and slice thickness. Depends only on selected computed tomography parameters and does not reflect patient dose.
Dose Limit
Maximum permissible occupational radiation dose.
Dose
Amount of radiant energy absorbed by an irradiated object.
Dosimeter
Instrument that detects and measures exposure to ionizing radiation.
Dosimetry
The practice of measuring the intensity of radiation.
Double contrast examination
Examination of the colon that uses air and barium for contrast.
Double emulsion film
Radiographic film that has an emulsion coating on both sides of the base and a layer of supercoat over each emulsion.
Double helix
configuration of DNA that is shaped like a ladder twisted about an imaginary axis like a spring.
Dynamic range
Range of values that can be displayed by an imaging system; shades of gray.
Eddy current
Current that opposes the magnetic field that induced it, creating a loss of transformer efficiency
Edge enhancement
Accentuation of the interface between different tissues.
Edge response function
Mathematical expression of the ability of the computed tomographic scanner to reproduce a high contrast edge with accuracy.
Effective atomic number
Weighted average atomic number for the different elements of a material.
Effective dose
Sum of specified tissues of the products of equivalent dose in a tissue and the weighting factor for the tissue. Effective dose is a method of converting a nonuniform radiation dose, as when a protective apron is worn, to a dose, with respect to risk, as if the whole body were exposed.
Effective dose equivalent
Sum of the products of the dose equivalent to a tissue and the weighting factors applicable to each of the tissues irradiated. The values are different for effective dose and effective dose equivalent.
Effective focal spot size
Area projected onto the patient and the image receptor.
Electric current
Flow of electrons
Electric field
Lines of force exerted on charged ions in the tissues by the electrodes that cause charged particles to move from one pole to another.
Electrical energy
Work that can be done when an electron or an electronic charge moves through an electric potential.
Electricity
form of energy created by the activity of electrons and other subatomic particles in motion.
Electrification
Process of adding or removing electrons from a substance.
Electrifiation
Process of adding or removing electrons from a substance.
Electrified object
Object that has too few or too many electrons.
Electrode
Electrical terminal or connector.
Electromagnet
Coil or wire wrapped around an iron core that intensifies the magnetic field.
Electromagnetic energy
Type of energy in x-rays, radio waves, microwaves, and visible light.
Electromagnetic radiation
Oscillating electric and magnetic field that travel in a vacuum with the velocity of light. Includes x-rays, gamma rays, and some nonionizing radiation (such as ultraviolet, visible, infrared, and radio waves).
Electromagnetic spectrum
Continuum of electromagnetic energy.
Electromotive force
Electric potential; measured in volts.
Electron binding energy
Strength of attachment of an electron to the nucleus.
Electron optics
Engineering aspects of maintaining proper electron to the nucleus
Electron spin
Momentum of a particle of an atom in a fixed pattern.
Electron volt
Unit of energy equal to that which an electron acquires from a potential difference of 1 V.
Electron
Elementary particle with one negative charge. Electrons surround the positively charged nucleus and determine the chemical properties of the atom.
Electrostatics
Study of fixed or stationary electric charge.
Element
Atoms that have the same atomic number and the same chemical properties. Substance that cannot be reduced further without changing its chemical properties.
Elemental mass
Characteristic mass of an element, determined by the relative abundance of isotopes and their respective atomic masses.
Elongation
Image that is made to appear longer than it really is because the inclined object is not located on the central x-ray beam.
Emulsion
Material with which x-rays or light photons from screens interact and transfer information.
Endoplasmic reticulum
Channel or series of channels that allows the nucleus to communicate with the cytoplasm.
Energy levels
Orbits around the nucleus that contain a designated number of electrons.
Energy subtraction
technique that uses the two x-ray beams alternately to provide a subtraction image that results from differences in photoelectric interaction.
Energy
Ability to do work; measured in joules.
Entrance roller
Roller that grips the film to begin its trip through the processor.
Entrance skin exposure
X-ray exposure to the skin; expressed in milliroentgen
Enzyme
Molecule that is needed in small quantities to allow a biochemical reaction to continue, even though it does not directly enter into the reaction.
Epithelium
Covering tissue that lines all exposed surfaces of the body, both exterior and interior.
Erg (joule)
Unit of energy and work
Excitation
Addition of energy to a system achieved by raising the energy of electrons with the use of x-rays.
Exit radiation
x-rays that remain after the beam exits through the patient.
Exposed matter
Matter that intercepts radiation and absorbs part or all of it; irradiated matter.
Exposure factors
Factors that influence and determine the quantity and quality of x-radiation to which the patient is exposed.
Exposure linearity
Ability of a radiographic unit to produce a constant radiation output for various combinations of mA and exposure time.
Exposure
Measure of the ionization produced in air by x-rays or gamma rays. Quantity of radiation intensit expressed in roentgen (R), Coulombs per kologram (C/kg), or air kerma (Gy).
Extinction time
Time required to end an exposure
Extrafocal radiation, off focus radiation
Electrons that bounce off the focal spot and land on other areas of the target.
Extrapolation
Estimation of a value beyond the range of known vaues
Falling load generator
Design in which exposure factors are adjusted automatically t the highest mA at the shortest exposure time allowed by the high voltage generator.
Fan beam
X-ray beam pattern used in computed tomography and digital radiography; projected as a slit.
Feed tray
The start of the transport system, where the film to be processed is inserted into the automatic processor in the darkroom.
Ferromagnetic material
Material that is strongly attracted by a magnet and that usually can be permanently magnetized by exposure to a magnetic field.
Field of view
Image matrix size provided by digital x-ray imaging systems.
Field
Interactions among different energies, forces, or masses that cannot be seen but can be described mathematically.
Fifteen percent rule
Principle that states that if the optical density on a radiograph is to be increased with the use of a kVp, an increase in kvP by 15% is equivalent to doubing of the mAs.
Filament
Part of the cathode that emits electrons, resulting in a tube current.
File
Collection of data or information that is treated as a unit by the computer.
Film badge
Pack of photographic film used for approximate measurement of radiation exposure to radiation workers. It is the most widely used and most economical type of personnel radiation monitor.
Film graininess
Distribution of silver halide grains in an emulsion.
Filtered back projection
Process by which an image acquired during computed tomography and stored in computer memory is reconstructed.
Filtration
Removal of low energy x-rays from the useful beam with aluminum or another metal. It results in increased beam quality and reduced patient dose.
First generation computed tomographic scanner
Finely collimated x-ray beam, single detector assembly that translates across the patient and rotates between successive translations.
Five percent rule
Principle that states that an increase of 5% in the kVp may be accompanied by a 30% reduction in the mAs to produce the same optical density at a slightly reduced contrast scale.
Fixing
Stage of processing during which the silver halide not exposed to radiation is dissolved and removed from the emulsion.
Fluorescence
Emission of visible light only during stimulation
Fluorescent screen
Cycle in a television picture tube whereby the electron beam creates the television optical signal and then immediately fades.
Fluoroscope
Device used to image moving anatomical structures with x-rays
Fluoroscopy
Imaging modality that provides a continuous image of the motion of internal structures while the x-ray tube is energized. Real time imaging.
Flux gain
Ratio of the number of light photons at the output phosphor to the number of x-rays at the input phosphor.
Focal spot
Region of the anode target in to produce x-rays.which electrons interact
Focal spot blur
Blurred region on the radiograph over which the technologist has little control.
Focused grid
Radiographic grid constructed so that the grid strips converge on an imaginary line.
Focusing cup
Metal shroud that surrounds the filament
Fog density
Development of silver grain that contains no useful information.
Fog
Unintended optical density on a radiograph that reduces contrast through light or chemical contamination.
Force
That which changes the motion of an object; a push or a pull. Expressed in newtons (N).
Foreshortening
Reduction in image size; related to the angle of inclination of the object
Fourth generator computed tomographic imaging system
Unit in which the x-ray source rotates but the detector assembly does not.
Fraction
Numeric value expressed by dividing one number by another.
Fractionated
Radiation dose delivered at the same dose in equal portions at regular intervals.
Free radical
Uncharged molecule that contains a single unpaired electron in the valence shell.
Frequency
Number of cycles or wavelengths of a simle harmonic motion per unit time. Expressed in Hertz (Hz). 1 Hz = 1 cycle/s.
Fulcrum
Imaginary pivot point bout which the x-ray tube and the image receptor move.
Full width at half maximum
Width of the profile at half its maximum value.
Full wave rectification
circuit in which the negative half cycle corresponding to the inverse voltage is reversed, so a positive voltage is always directed across the x-ray tube.
Fundamental laws of motion
The three principles of inertia, force, and action/reaction established by Isaac Newton.
Fundamental particles
The three primary constituents of an atom: electrons, photons, and neutrons.
Gantry
Portion of the computed tomographic or magnetic resonance imaging system that accommodates the patient and source or the detector assemblies.
Gelatin
Part of the emulsion that provides mechanical support for the silver halide crystals by holding them uniformly dispersed in place.
Gonadal dose
Exposure to the reproductive organs
Gradient
Slope of the tangent at any point on the characteristic curve.
Gray (Gy)
Special name for the SI unit of absorbed dose and air kerma. 1 Gy = 1 J/kg = 100 rad.
Gray scale
Image display in which intensity is recorded as variations in brightness.
Grid cleanup
Ability of a grid to absorb scatter radiation.
Grid cutoff
Absence of optical density on a radiograph caused by unintended x-ray absorption in a grid.
Grid frequency
Number of grid lines per inch or centimeter.
Grid lines
Series of sections of radiopaque material.
Grid ratio
Ratio of grid height to grid strip separation.
Grid
Device used to reduce the intensity of scatter radiation in the remnant x-ray beam.
Grid controlled tube
X-ray tube designed to be turned on and off very rapidly for situations that require multiple exposures at precise exposure times.
Guanine
Nitrogenous organic base that attaches to a deoxyribose molecule.
Halation
Reflection of screen light transmitted through the emulsion and base.
Half-life
Time required for a quantity of radioactivity to be reduced to half its original value.
Half-value layer (HVL)
Thickness of absorber necessary to reduce an x-ray beam to half its original intensity.
Half wave rectification
Condition in which the voltage is not allowed to swing negatively during the negative half of its cycle.
Hard copy
Permanent image on film or paper, as opposed to an image on a cathode ray tube, a disc, or magnetic tape.
Hard x-ray
X-ray that has high penetrability and therefore is of high quality.
Hardener
A chemical, usually potassium glutaraldehyde alum in the fixer, that is used to stiffen and shrink the emulsion.
Hardware
Visible parts of the computer
Heel effect
Absorption of x-rays in the heel of the target, resulting in reduced x-ray intensity to the anode side of the central axis.
Hertz (Hz)
Unit of frequency; the number of cycles or oscillations that occur each second during simple harmonic motion.
Hexadecimal number system
Number system used by low level applications to represent a set of four bits.
High contrast resolution
Ability to image small objects with high subject contrast; spatial resolution
High voltage generator
One of the three principal parts of an x-ray imaging system; it is always close to the x-ray tube.
Homeostasis
a. State of equilibrium among tissue and organs. b. Ability of the body to return to normal function despite infection and environmental changes.
Hormone
Protein manufactured by various endocrine glands and carried by the blood to regulate body functions such as growth and development.
Horsepower
British unit of power
Hounsfield unit
Scale of computed tomographic numbers used to assess the nature of tissue.
Hypersthenic
Referring to a body habitus of a patient who is large in frame and overweight.
Hythenicpo Retention
Undesirable retention of the fixer in emulsion.
Hypo
Sodium thiosulfate, a fixing agent that removes unexposed and undeveloped silver halide crystals from the emulsion.
Hyposthenic
Referring to a body habitus of a patient who is thin but healthy looking.
Hysteresis
Additional resistance created by the alternate reversal of the magnetic field caused by the alternating current.
Image detail
Sharpness of small structures on the radiograph
Image intensifier
Electronic vacuum tube that amplifies a fluoroscopic image to reduce patient dose.
Image matrix
Layout of cells in rows and columns.
Image noise
Deterioration of the radiographic image
Image receptor
Medium that transforms the x-ray beam into a visible image; radiographic film or a phosphorescent screen.
Image receptor contrast
Contrast that is inherent in the film and is influenced by processing of the film.
Image forming x-ray
X-ray that exits from the patient and enters the image receptor.
Improper fraction
Fraction in which the quotient is greater than 1.
Indirect effect
Effect of radiation that results from the production of free radicals produced by the interaction of radiation with water.
Induction motor
Electric motor in which the rotor is a series of wire loops but the external magnetic field is supplied by several fixed electromagnets called stators.
Induction
Process of making ferromagnetic material magnetic.
Inertia
Property of matter that resists change in motion or at rest.
Infrared light
Light that consists of photons with wavelengths longer than those of visible light but shorter than those of microwaves.
Infrared radiation
Electromagnetic radiation just lower in the energy than visible light, with a wavelength in the range of 0.7 to 1000 um
Inherent filtration
Filtration of useful x-ray beams provided by the permanently installed components of an x-ray tube housing assembly and the glass window of an x-ray tube.
Initiation time
Time required to start an exposure
input
Process of transferring information into primary memory
Insulator
Material that inhibits the flow of electrons within a conductor or during heat transfer.
Integrate mode
Function of an instrument designed to measure the total accumulated intensity of radiation over time.
Intensification Factor
Ratio of exposure without screens to that with screens to produce the same optical density.
Intensifying screen
Sensitive phosphor that converts x-rays to light to shorten exposure time and reduce patient dose.
Intensity profile
Projection formed by the intensity of radiation detected according to the attenuation pattern.
International System of Units (SI)
Standard system of units based on the meter, the kilogram, and the second; it has been adopted by all countries and is used in all branches of science.
Interphase
Period of growth of the cell between divisions
Interpolation
Estimation of a value between two known values
Interrogation time
Time during which the signal from an image detector is sampled.
Interspace material
Sections of radiolucent material in a grid.
Inverse square law
Law that states that the intensity of radiation at a location is inversely proportional to the square of its distance from the source of radiation.
Inverse voltage
Current that flows from the anode to the cathode
Inverter
High speed switches that convert direct current into a series of square pulses.
Ion chamber
Instrument that detects and measures the radiation intensity in areas outside of protective barriers.
Ion pair
Two oppositely charged particles.
Ion
Atom with too many or too few electrons; an electrically charged particle.
Ionic bond
Bonding that occurs because of an electrostatic force between ions.
Ionization potential
Amount of energy (34 eV) necessary to ionize tissue atoms.
Ionization
Removal of an orbital electron from an atom.
ionized
Referring to an atom that has an extra electron or has had an electron removed.
Ionizing radiation
Radiation capable of ionization
Irradiated
Referring to matter that intercepts radiation and absorbs part or all of it; exposed.
Isobars
Atoms that have the same number of nucleons but different numbers of protons and neutrons.
Isochromatid
Fragment in a chromosome aberration.
Isomers
Atoms that have the same numbers of protons and neutrons but a different nuclear energy state.
Isotones
Atoms that have the same number of neutrons.
Isotopes
Atoms that have the same number of protons but a different number of neutrons.
Isotropic
Equal intensity in all directions; having the same properties in a directions.
Joule (J)
Unit of energy; the work done when a force of 1 N acts on an object along a distance of 1 m.
Kerma
Energy absorbed per unit mass from the initial kinetic energy released in matter of all the electrons liberated by x-rays or gamma rays. Expressed in gray (Gy)
Kilo
Prefix meaning “1000”
Kilogram
Scientific unit of mass that is unrelated to gravitational effects; 1000g
Kilovolt
Electric potential equal to 1000 V.
Kilovolt peak
Measure of the maximum electrical potential across an x-ray tube; expressed in kilovolts.
Kinetic energy
Energy of motion
Latent image center
Sensitivity center that has many silver ions attracted to it.
Latent image
Unobservable image stored in the silver halide emulsion; it is made manifest by processing.
Latent period
Period after the prodromal stage of the acute radiation syndrome during which no sign of radiation sickness is apparent.
Lateral decentering
Improper positioning of the grid that results in cuttoff.
Latitude
Range of x-ray exposure over which a radiograph is acceptable
Law of conservation of energy
Principle that states that energy may be transformed from one form to another but cannot be created or destroyed; the total amount of energy is constant.
Law of conservation of matter
Principle that states that matter can be neither created nor destroyed.
Law of inertia
Principle that states that a body will remain at rest or will continue to move with a constant velocity in a straight line unless acted on by an external force.
LD 50/60
Dose of radiation expected to cause death within 60 days to 50% of those exposed.
Leakage radiation
Secondary radiation emitted through the tube housing
Limiting resolution
Spatial frequency at a modulation transfer function equal to 0.1.
Line focus principle
Design incorporated into x-ray tube targets to allow a large area for heating while a small focal spot is maintained.
Line focus
Projection of an inclined line onto a surface, resulting in a smaller size.
Line pair
One bar and its interspace of equal width.
Line energy transfer (LET)
Measure of the rate at which energy is transferred from ionizing radiation to soft tissue. Expressed in kiloelectron volts per micrometer of soft tissue.
Linear tomography
Imaging modality in which the x-ray tube is mechanically attached to the image receptor and moves in one direction as the image receptor moves in the opposite direction.
Linear, nonthreshold
Referring to the dose-response relationship that intersects the dose axis at or below zero.
Linear, threshold
Referring to the dose-response relationship that intercepts the dose axis at a value greater than zero
Log relative exposure (LRE)
change in optical density over each exposure interval.
Long gray scale
Low contrast radiograph that has many shades of gray
Look-up table
Matrix of data that manipulates the values of gray levels, converting an image input value to a different output value.
Low contrast resolution
Ability to image objects with similar subject contrast
Luminescence
Emission of visible light
Lymphocyte
White blood cell that plays an active role in providing immunity for the body by producing antibodies; it is the most radio sensitive blood cell.
Lysosome
Cell that contains enzymes capable of digesting cellular fragments.
Magnetic dipole moment
Vector with a magnitude equal to the product of the current that flows in a loop and the area of the current loop.
Magnetic dipole
Current that flows in an infinitesimally small loop.
Magnetic domain
An accumulation of many atomic magnents with their dipoles aligned.
Magnetic domain
An accumulation of many atomic magnets with their dipoles aligned.
Magnetic permeability
Property of a material that causes it to attract the imaginary lines of the magnetic field.
Magnetic Susceptibility
The ease with which a substance can be magnetized.
Magnetism
The polarization of a material.
Magnetite
The magnetic oxide of iron.
Magnetization
Relative magnetic flux density in a materia compared with that in a vacuum.
Magnification
Condition in which the images on the radiograph are larger than the object they represent.
Magnitude
Number that represents a quantity.
Main-chain scission
Breakage of the long chain macromolecule that divides the long, single molecule into smaller ones.
Mainframe computer
A fast, medium-to- large-capacity system that has multiple microprocessors.
Manifest image
The observable image that is formed when when the latent image undergoes proper chemical processing.
Man-made radiation
X-rays and artificially produced radionuclides used for nuclear medicine.
Mass density
Quantity of matter per unit volume.
Mass
A quantity of matter; expressed in kilograms.
Mass energy equivalence
Energy equals mass multiplied by the square of the speed of light.
Matrix
Rows and columns of pixels displayed on a digital image.
Matter
Anything that occupies space and has form or shape.
Maximum permissible dose
Dose of occupational radiation that would be expected to produce no significant radiation effects. An old expression. Replaced by Dose Limit.
Mean lethal dose
Constant related to the radio sensitivity of a cell.
Mean marrow dose
Average radiation dose to the entire active bone marrow.
Mean Survival Time
Average time between exposure and death.
Mechanical energy
Ability of an object to do work.
Meiosis
Process of germ cell division that reduces the chromosomes in each daughter cell to half the number of chromosomes in the parent cell.
Metabolism
Anabolism and catabolism
Metaphase
Phase of cell division during which the chromosomes are divisible.
Metol
Secondary constituent used in the chemical composition of developing agents.
Microcalcifications
Calcific deposits that appear as small grains of varying sizes on the x-ray film
Microcomputer
Personal computer or electronic organizer
Microcontroller
Tiny computer installed in an appliance.
Microfocus tube
Tube that has a very small focal sot and that is specifically designed for imaging very small microcalcifications at relatively short source to image distances
Milliampere (mA)
Measure of x-ray tube current.
Milliampere second (mAs)
Product of exposure time and x-ray tube current; measure of the total number of electrons.
Mitochondrion
Structure that digests macromolecules to produce energy for the cell.
Mitosis
process of somatic cell division wherein a parent cell divides to form two daughter cells identical to the parent cell.
Modem
Device that converts digital information into analog information.
Modulation transfer function
Mathematical procedure for measuring resolution
Modulation
Changing of the magnitude of a video signal; the magnitude is directly proportional to the light intensity received by the television camera tube.
Molecule
Group of atoms of various elements held together by chemical forces; the smallest unit of a compound that can exist by itself and retain all its chemical properties.
Molybdenum
Target material for x-ray tube s that is used in mammography.
Momentum
Product of the mass of an object and its velocity.
Monoenergetic
Beam that contains x-rays or gama rays that all have the same energy.
Monosaccharide
A sugar
Motherboard
Main circuit board in a system unit.
Motion blur
Blurring of the image that results from movement of the patient or the x-ray tube during exposure.
Moving grid
Grid that moves while the x-ray exposure is being made.
National Council on Radiation Protection and Measurement
Organization that continuously reviews recommended dose limits.
Natural environmental radiation
Naturally occurring ionizing radiation, including cosmic rays, terrestrial radiation, and internally deposited radionuclides.
Natural magnet
Magnet that gets its magnetism from the Earth
Nervous tissue
Tissue that consists of neurons and serves as the avenue through which electrical impulses are transmitted throughout the body for control and response.
Neuron
Cell of the the nervous system that has long, thin extensions from the cell to distant parts of the body.
Neutron
Uncharged elementary particle, with a mass slightly greater than that of the proton, that is found in the nucleus of every atom heavier than hydrogen.
Newton (N)
Unit of force in the SI system; 1 N =0.22 lb.
Node
One of many stations or terminals of a computer network.
Noise
a. Grainy or uneven appearance of an image caused by an insufficient number of primary x-rays. b. uniform signal produced by scattered x-rays.
Nonionizing radiation
Radiation for which the mechanism of action in tissue does not directly ionize atomic or molecular systems through a single interaction.
Nonlinear, nonthreshold
Referring to varied responses that are produced from varied doses, with any dose expected to produce a response.
Nonlinear, threshold
Referring to varied responses that are produced from varied doses, with a particular level below which there is no response.
Nonstochastic effects
Biologic effects of ionizing radiation that demonstrate the existence of a threshold. Severity of biologic damage increases with increased dose.
North pole
Magnetic pole that has a positive electrostatic charge.
Nuclear Energy
Energy contained within the nucleus of an atom.
Nucleolus
Rounded structure that often is attached to the nuclear membrane and controls the passage of molecules, especially RNA, from the nucleus to the cytoplasm.
Nucleon
A proton or a neutron.
Nucleotide
Unit formed from a nitrogenous base, a five carbon sugar molecule, and a phosphate molecule.
Nucleus
a. Center of a living cell; spherical mass of protoplasm that contains the the genetic material (DNA) that is stored in its molecular structure. b. Center of an atom that contains neutrons and protons.
Nuclide
General term that refers to all known isotopes, both stable and unstable, of chemical elements.
Object plane
Plane in which the anatomical structures that are to be imaged lie.
Object to image receptor distance
Distance from the image receptor to the object that is to be imaged.
Occupational dose
Dose received by an individual in a restricted area during the course of employment in which the individual’s assigned duties involve exposure to radiation.
Occupational exposure
Radiation exposure received by radiation workers.
Off focus radiation
X-rays produced in the anode but not at the focal spot.
Off level grid
Artifact produced by an improperly positioned radiographic tube not by an improperly positioned grid.
Oocytes
Primordial follicles that grow to encapsulate oogonia.
Opaque
Surface that does not allow the passage of light.
Open filament
Condition that results when the filament becomes thinner and breaks.
Operating console
Console that allows the radiologic technologist to control the x-ray tube current and voltage so that the useful x-ray beam is of proper quantity and quality.
Operating system
Series of instructions that organizes the course of data through the computer to solve a particular problem.
Optical density
Degree of blackening of a radiograph.
Optical disc
Removable disc that uses laser technology to write and read data.
Ordered pairs
Notation for coordinates in which the first number of the pair represents a distance along the x-axis and the second number indicates a distance up the y-axis.
Organ system
Combination of tissues and organs that forms an overall integrated organization.
Organic molecule
Molecule that is life supporting and contains carbon.
Organs
Collection of tissues of similar structure and function.
Origin
Point at which two axes meet on a graph.
Orthochromatic
Referring to blue or green sensitive film; usually exposed with rare Earth screen.
Outcome analysis
Image interpretation that involves reconciling the patient’s ultimate disease condition with the radiologist’s diagnosis.
Output
Process of transferring the results of a computation from primary memory to storage or to the user.
Overcoat
Protective covering of gelatin that encloses the emulsion.
Overexposed
Referring to a radiograph that is too dark because too much x-radiation reached the image receptor.
Oxidation
Reaction that reduces an electron
Oxygen enhancement ratio
Ratio of the dose necessary to produce a given effect under anoxic conditions to the dose necessary to produce the same effect under aerobic conditions.
Pair production
Interaction between the x-ray and the nuclear electric field that causes the x-ray to disappear and that causes two electrons–one positive and one negative–to take its place.
Panchromatic
Referring to film that is sensitive to the entire visible light spectrum.
Parallel circuit
Circuit that contains elements that bridge conductors rather than lie in a line along a conductor.
Parallel grid
Simple grid in which all lead grid strips are parallel.
Paramagnetic
Referring to materials slightly attracted to a magnet and loosely influenced by an external magnetic field.
Parenchymal
Referring to part of the organ that contains tissues representative of that particular organ.
Partial volume effect
Distortion of signal intensity from a tissue because it extends partially into an adjacent slice thickness.
Particle accelerator
An atom “smasher.” Cyclotron. Linear Accelerator.
Particulate radiation
Radiation distinct from x-rays and gamma rays; examples include alpha particles, electrons, neutrons, and protons.
Penetrability
Ability of an x-ray to penetrate tissue; range in tissue; x-ray quality.
Penetrometer
Aluminum step wedge
Penumbra
Image blur that results from the size of the focal spot; geometric unsharpness.
Permanent magnent
Magnet whose magnetism is induced artificially
Phantom
Device that simulates some parameters of the human body for evaluation of imaging system performance.
Phenidone
Secondary constituent in the chemical composition of developing agents.
Phosphor
Active layer of the radiographic intensifying screen closest to the radiographic film.
Phosphorescence
Emission of visible light during and after stimulation
Photoconductor
Material that conducts electrons when illuminated.
Photoconductor
Material that conducts electrons when illuminated.
Photodiode
Solid state device that converts light into an electric current.
Photodisintegration
Process by which very high energy x-rays can escape interaction with electrons and the nuclear electric field and can be absorbed directly by the nucleus.
Photoelectric effect
Absorption of an x-ray by ionization
photoelectron
Electron that has been removed during the process of photelectric absorption.
Photoemission
Electron emission after light stimulation.
Photographic effect
formation of the latent image.
Photometer
Instrument that measures light intensity.
Photomultiplier tube
Electron tube that converts visible light into an electrical signal.
Photon
Electromagnetic radiation that has neither mass nor electric charge but interacts with matter as though it is a particle; x-rays and gamma rays.
Photospot camera
Camera that exposes only one frame when active, receiving its image from the output phosphor of the image intenbsifier tube.
Photostimulation
Emission of visible light after excitation by laser light.
Photothermographic
Printing process by which film is exposed to light, thereby forming a latent image that is made visible by heat.
Phototimer
Device that allows automatic exposure control.
Pixel
Picture element; the cell of a digital image matrix.
Planck’s constant
Fundamental physical constant that relates the energy of radiation to its frequency.
Planetary rollers
Rollers positioned outside the master roller and guide shoes.
Pluripotential stem cell
Stem cell that has the ability to develop into several differnt types of mature cells.
Pocket ionization chamber (Pocket dosimeter)
Personnel radiation monitoring device.
Point lesion
Any change that results in impairment or loss of function at the point of a single chemical bond.
Point mutation
Molecular lesion caused by the change or loss of a base that destroys the triplet code and may not be reversible.
Polarity
Existence of opposing negative and positive charges.
Pole
Magnetically charged end of a material.
Polyenergetic
Referring to radiation, such as x-rays with a spectrum of energies.
Polysaccharide
Large carbohydrate that includes starches and glycogen.
Positive beam limiting (PBL)
Feature of radiographic collimators that automatically adjusts the radiation field to the size of the image receptor.
Potassium bromide
Compound used as a restrainer in the developer.
Potassium iodide
Compound used as a restrainer in the developer
Potential energy
Ability to do work by virtue of position
Power
Time rate at which work (w) is done. 1 W = 1 J/s.
Precursor cell
An immature cell.
Predetector collimator
Collimator that restricts the x-ray beam viewed by the detector array.
Prepatient collimator
Collimator that consists of several sections so that a nearly parallel x-ray beam results.
Prereading voltmeter
A kVp meter that registers even though an exposure is not being made and no current is flowing within the circuit; this allows the voltage to be monitored before an exposure.
Preservative
Chemical additive, usually sodium sulfide, which maintains the chemical balance of the developer and fixer.
Preventive maintenance
Planned program of parts replacement at regular intervals.
Primary coil
The first coildd through which the varying current in an electromagnet is passed.
Primary protective barrier
Any wall to which the useful beam can be directed.
Processing
Chemical treatment of the emulsion of a radiographic film to change a latent image to a manifest image.
Processor
Electronic circuitry that does the actual computations and the memory that supports it.
Prodromal period
First stage of the acute radiation syndrom; occurs within hours after radiation exposure.
Prone
Having the front or ventral surface downward. Lying flat or prostrate.
Proper fraction
Fraction in which the quotient is less than 1.
Prophase
Phase of cell division during which the nucleus and the chromosomes enlarge and the DNA begins to take structural form.
Proportion
The relation of one part to another.
Proportional counter
Sensitive instrument that is used primarily as stationary laboratory instrument for the assay of small quantities of radioactivity.
Protective coating
Layer of the radiographic intensifying screen closest to the radiographic film.
Protective housing
Lead lined metal container into which the x-ray tube is fitted.
Protein synthesis
Metabolic production of proteins
Proton
Elementary particle with a positive electric charge equal to that of an electron and a ass approximately equal to that of a neutron. It is located within the nucleus of an atom.
Protracted dose
Dose of radiation that is delivered continuously bu at a lower dose rate.
Pulse mode/rate mode
Instruments designed to detect the p resence of radiation.
Quality assurance
All panned and systematic actions necessary to provide adequate confidence that a facility, system, or administrative component will perform safely and satisfactorily in service to a patient. It includes scheduling, preparation, and promptness in examination or treatment, reporting of results, and quality control.
Quality Control
All actions necessary to control and verify the performance of equipment; part of quality assurance.
Quantum mottle
Radiographic noise produced by the random interaction of x-rays with an intensifying screen. This effect is more noticeable when very high rare Earth systems are used at a high kVP.
Quantum theory
Theory in the physics of matter smaller than an atom and of electromagnetic radiation.
Quantum
An x-ray photon
Rad (radiation absorbed dose)
Special unit for absorbed dose and air kerma. 1 rad =100 erg/g= 0.01 Gy.
Radiation (thermal)
Transfer of heat by the emission of infrared electromagnetic radiation.
Radiation biology
Branch of biology that is concerned with the effects of ionizing radiation on living systems.
Radiation exposure
X-ray quantity or intensity; measured in roentgens.
Radiation fog
Artifact caused by unintentional exposure to radiation.
Radiation hormesis
Theory that suggest that very low radiation doses may be beneficial.
Radiation quality
Relative penetrability of an x-ray beam determined by its average energy; usually measured by half value layer or kilovolt peak.
Radiation quantity
Intensity of radiation; usually measured in milliroentgen
Radiation safety officer
That individual physician, medical physicist, or technologist assigned to develop and implement the radiation safety program.
Radiation standards
Recommendations, rules, and regulations regarding permissible concentrations, as well as safe handling techniques, transportation, and industrial control of radioactive material.
Radiation weighting factor
Factor used for radiation protection that accounts for differences in biologic effectiveness between different radiations Formerly called quality factor.
Radiation
Energy emitted and transferred through matter.
Radioactive decay
Naturally occurring process whereby an unstable atomic nucleus relieves its instaility through the emission of one or more energetic particles.
Rad (radiation absorbed dose)
Special unit for absorbed dose and air kerma. 1 rad =100 erg/g= 0.01 Gy.
Radiation (thermal)
Transfer of heat by the emission of infrared electromagnetic radiation.
Radiation biology
Branch of biology that is concerned with the effects of ionizing radiation on living systems.
Radiation exposure
X-ray quantity or intensity; measured in roentgens.
Radiation fog
Artifact caused by unintentional exposure to radiation.
Radiation hormesis
Theory that suggest that very low radiation doses may be beneficial.
Radiation quality
Relative penetrability of an x-ray beam determined by its average energy; usually measured by half value layer or kilovolt peak.
Radiation quantity
Intensity of radiation; usually measured in milliroentgen
Radiation safety officer
That individual physician, medical physicist, or technologist assigned to develop and implement the radiation safety program.
Radiation standards
Recommendations, rules, and regulations regarding permissible concentrations, as well as safe handling techniques, transportation, and industrial control of radioactive material.
Radiation weighting factor
Factor used for radiation protection that accounts for differences in biologic effectiveness between different radiations Formerly called quality factor.
Radiation
Energy emitted and transferred through matter.
Radioactive decay
Naturally occurring process whereby an unstable atomic nucleus relieves its instability through the emission of one or more energetic particles.
Radioactive disintegration
Process by which the nucleus spontaneously emits particles and energy and transforms itself into another atom to reach stability.
Radioactive half life
Time required for a radioisotope to decay to half its original activity.
Radioactivity
Rate of decay or disintegration of radioactive material. Expressed in curie or becquerel.
Radiolysis of water
Dissociation of water into other molecular products as a result of irradiation.
Radiographer
Radiologic technologist who deals specifically with x-ray imaging.
Radiographic contrast
Combined result of image receptor contrast and subject contrast.
Radiographic intensifying screen
Device that converts the energy of the x-ray beam into visible light to increase the brightness of an x-ray image.
Radiographic noise
Undesirable fluctuation in the optical density of the image.
Radiographic technique chart
Guide that describes standard methods for consistently producing high quality images.
Radiographic technique
Combination of settings selected on the control panel of the x-ray imaging system to produce a quality image on the radiograph.
Radiography
Imaging modality that uses x-ray film and usually an x-ray tube mounted from the ceiling on a track that allows the tube to be moved in any direction; provides fixed images.
Radioisotopes
Radioactive atoms that have the same number of protons. They are changed into a different atomic species by disintegration of the nucleus accompanied by the emission of ionizing radiation.
Radiological Society of North America (RSNA)
Scientific society of radiologists and medical physicists.
Radiolucent
Referring to a tissue or material that transmits x-rays and appears dark on a radiograph.
Radiolysis of water
Dissociation of water into other molecular products as a result of irradiation.
Radiolucent
Referring to a tissue or material that transmits x-rays and appears bright on a radiograph.
Radionuclides
Any nucleus that emits radiation.
Radiopaque
Referring to a tissue or material that absorbs x-rays and appears bright on a radiograph.
Radiosensitivity
Relative susceptibility of cells, tissues, and organs to the harmful action of ionizing radiation.
Radon
Colorless, odorless, naturally occurring radioactive gas that decays via alpha emission and has a half life of 3.8.
Random access memory (RAM)
Data that can be stored or accessed at random from anywhere in main memory in approximately equal amounts of time, regardless of where they are located.
Rare Earth Element
Element that is a transitional metal found in low abundance in nature.
Rare Earth screen
Radiographic intensifying screen made from rare Earth elements, which make it more useful for radiographic imaging.
Raster Pattern
Pattern produced on the screen of a televsion picture tube by the movement of an electron beam or on film by a laser scan.
Ratio
Mathematical relationship between similar quantities
Read only memory
Data storage device that contains information supplied by the manufacturer that cannot be written on or erased.
Real time
Display for which the image is continuously renewed, often to view anatomical motion, in fluoroscopy and ultrasound.
Reciprocity law
Principle that states that optical density on a radiograph is proportional only to the total energy imparted to the radiographic film.
Reconstruction time
Time needed for the compujter to present a digital image after an examination has been completed.
Reconstruction
creation of an image from data.
Recorded detail
Degree of sharpness of structural lines on a radiograph.
Recovery
Repair and repopulation.
Rectification
Process of converting alternating current to direct current.
Rectifier
Electronic device that allows current flow in only one direction.
Red filter
Filter that transmits light only above 600 nm; it is used with both green and blue senstive film
Reducing agent
chemical responsible for reduction.
Reduction
Process by which an electron is given up by a chemical to neutralize a positive ion.
Reflection
Return or reentry of an x-ray.
Reflection
Return or reentry of an x-ray.
Refective layer
Layer of the intensifying screen that intercepts light headed in other directions and redirects it to the film.
Refraction
Deviation of course that occurs when photons of visible light traveling in straight lines pass from one transparent medium to another.
Region of interest (ROI)
Area of an anatomical structure on a reconstructed digital image as defined by the operator using a cursor.
Relative age-response relationship
Increased incidence of a disease proportional to its natural incidence.
Relative age response relationship
Increased incidence of a disease proportional to its natural incidence.
Relative biologic effectiveness (RBE)
Ratio of the dose of standard radiation necessary to produce a given effect to the dose of test radiation needed for the same effect.
Relative risk
Estimation of late radiation effects in large populations without precise knowledge of their radiation dose.
Relay
Electrical device based on electromagnetic induction that serves as a switch.
Rem (radiation equivalent man)
Special unit for dose equivalent and effective dose. It has been replaced by the sievert (sv) in the SI system. 1 rem =0.01Sv.
Remnant radiation
X-rays that ass through the patient and interact with the image receptor.
Replenishment
Replacement of developer and of fixer in the automatic processing of film.
Resistance
Opposition to a force.
Resolution
Measure of the ability of a system to image two separate objects and visually distinguish one from the other.
Restrainer
Compound that restricts the action of the developing agent to only irradiated silver halide crystals.
Ribonucleic acid (RNA)
Molecules that are involved in the growth and development of a cell through a number of small, spherical cytoplasmic organelles that attach to the endoplasmic reticulum.
Ribosomes
the site of protein synthesis
right hand rule
Rule by which the direction of magnetic field lines can be determined.
Rotating anode
Anode used in general purpose x-ray tubes because the tubes must be capable of producing high intensity x-ray beams in a short time.
Rotor
Rotating part of an electromagnetic induction motor that is located inside the glass envelope.
Secondary protective barrier
Barrier designed to shield an area from secondary radiation.
Sagittal plane
Any anterior posterior plane parallel to the long axis of the body.
Saturation current
filament current that has risen to its maximum value because all available electrons have been used.
Scalar
referring to a quantity or a measurement that has only magnitude.
Scatter Radiation
X-rays scattered back in the direction of the incident x-ray beam.
Scintillation detector
Instrument used in the detector arrays of many computed tomographic scanners.
Screen lag
The phosphorescence in an intensifying screen.
Screen speed
Relative number used to identify the efficiency of conversion of x-rays into usable light.
Screen film
The most commonly used film; used with intensifying screens.
Secondary coil
coil in which induced current in an electromagnet flows
Secondary electron
Electron ejected from the outer shell of an atom
Secondary memory
Data stored on tape drives, diskettes, and hard disc drives.
Secondary protective barrier
Barrier designed to shield an area from secondary radation.
Secondary radiation
leakage and scatter reaction
Zonography
Thick slice tomography with a tomographic angle of less than 10 degrees`
Y-axis
Vertical line of a graph
x-ray
Penetrating, ionizing electromagnetic radiation that has a wavelength much shorter than that of visible light.
x-ray tube rating charts
Charts that guide the technologist in the use of xray tubes.
x-ray quantity
Output intensity of an x-ray imaging system; measured in roentgens (r).
x-ray quality
Penetrability of an x-ray beam.
