Physics Flashcards
(665 cards)
1
Q
Matter
A
Anything that occupies space and has mass.
2
Q
Atoms
A
All matter is composed of fundamental building blocks
3
Q
Mass
A
is the quantity of matter as described by its energy equivalence.
4
Q
Weight
A
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.
5
Q
Mass
A
measured in kilograms
6
Q
Kilo
A
stands for 1000
7
Q
Building blocks of matter
A
atoms and molecules
8
Q
Energy
A
is the ability to do work
9
Q
Potential Energy
A
the ability to do work by virtue of position.
10
Q
Kinetic energy
A
is the energy of motion
11
Q
Chemical energy
A
energy released by a chemical reaction
12
Q
Electrical energy
A
represents the work that can be done when an electron moves through an electron potential difference (voltage).
13
Q
Thermal energy
A
energy of motion at the molecular level
14
Q
Nuclear energy
A
energy that is contained within the nucleus of an atom.
15
Q
Electromagnetic energy
A
x-rays, radio waves, microwaves; and ultraviolet, infrared, and visible light.
16
Q
Mass-Energy (Einstein)
E=mc^2
A
Where E is energy, m is mass, and c is the velocity (speed) of electromagnetic radiation (light) in a vacuum
17
Q
Radiation
A
energy emitted and transferred through space
18
Q
Electromagnetic radiation
A
visible light, a form of electromagnetic energy, is radiated by the sun.
19
Q
Electromagnetic energy
A
usually referred to as electromagnetic radiation or, simply, radiation.
20
Q
Exposed or Irradiated
A
Matter that intercepts radiation and absorbs part or all of it.
21
Q
Ionizing radiation
A
is a special type of radiation that includes x-rays.
22
Q
Ionization
A
is the removal of an electron from an atom
23
Q
Ion pair
A
Two opppositely charged particles
24
Q
1% voltage ripple
A
High frequency generators that higher x-ray quantity and quality
25
100% voltage ripple
Single phase power in which the voltage varies from zero to its maximum value
26
14% ripple
Three-phase, six pulse power whose voltage supplied to the x-ray tube never falls below 86% of peak value.
27
4% voltage ripple
Three phase, 12 pulse power whose voltage supplied to the x-ray tube never falls below 96% of peak value.
28
Abrasion layer
Protective covering of gelatin that encloses an emulsion.
29
Absorbed dose
Energy transferred from ionizing radiation per unit mass of irradiated material; expressed in rad (100 erg/g) or gray (1 J/kg).
30
Absorption blur
Characteristic of a subject that affects subject contrast
31
Absorption
Transfer of energy from an electromagnetic field to matter; removal of x-rays from a beam via the photoelectric effect.
32
Acceleration
Rate of change of velocity over time
33
Acceleration of gravity
constant rate at which objects falling to the Earth accelerate.
34
Acetic acid
chemical used in the stop bath
35
Activator
chemical, usually acetic acid in the fixer and sodium carbonate in the developer, used to neutralize the developer and swell the gelatin.
36
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.
37
Actual focal spot size
Area on the anode target that is exposed to electrons from the tube current.
38
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.
39
Adhesive layer
Protective covering of gelatin that encloses the emulsion
40
Aerial oxidation
Oxidation that occurs when air is introduced into the developer after it is mixed, handled, and stored.
41
Afterflow
phosphorescence in an intensifying screen.
42
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.
43
ALARA
As low as reasonably achievable
44
Algorithm
Computer adapted mathematical calculation applied to raw data during image reconstruction
45
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.
46
Alternating current (AC)
Oscillation of electricity in both directions within a conductor.
47
Amber filter
Filter that transmits light with wavelengths longer than 550 nm, which is above the spectral response of blue sensitive film
48
Ammeter
Device that measures current
49
Ampere (A)
SI unit of electric charge: 1 A = 1 C/s
50
Amplitude
Width of a waveform
51
Anabolism
Process of synthesizing smaller molecules into a larger macromolecule.
52
Anaphase
Third phase of mitosis, during which chromatids repel one another and migrate along the mitotic spindle to opposite sides of the cell.
53
Anatomically programmed radiography (APR)
Technique by which graphics on the console guide the technologist in selection of a desired kVp and mAs.
54
Anode
Positively charged side of an x-ray tube that contains the target.
55
Anthropomorphic
Human characteristics
56
Aperture diaphragm
Simple beam restricting device that attaches a lead-lined metal diaphragm to the head of the x-ray tube.
57
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.
58
Archival quality
Attribute that refers to the fact that the image does not deteriorate with age but remains in its original state.
59
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.
60
Array processor
Part of a computer that handles raw data and performs the mathematical calculations necessary to reconstruct a digital image.
61
Artifact
Unintended optical density on a radiograph or another film type image receptor.
62
Asthenic
Referring to the body habitus of a patient who is small and frail.
63
Atom
Smallest particle of an element that cannot be divided or broken by chemical means.
64
Atomic mass number
Number of protons plus number of neutrons in the nucleus.
65
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.
66
Atomic mass
Relative mass of a specific isotope of an element.
67
Atomic number (Z)
Number of protons in the nucleus.
68
Atrophy
Shrinking of a tissue or organ.
69
Attenuation
Reduction in radiation intensity that results from absorption and scattering.
70
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.
71
Automatic exposure control (AEC)
Feature that determines radiation exposure during radiography in most x-ray imaging systems.
72
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.
73
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.
74
Average gradient
Measure of radiographic contrast
75
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.
76
Axial
perpendicular to the long axis of the body
77
Backscatter radiation
X-rays that have interacted with an object and are deflected backward.
78
Bandpass
Number of times per second that the electron beam can be modulated.
79
Base density
Optical density inherent in the base of the film.
80
Base plus fog
Average density from an unexposed area of the strips.
81
Base
Area that serves as a mechanical support for the active phosphor layer in a radiographic intensifying screen.
82
Beam axis
Central line that represents maximal ultrasound or xray intensity
83
Beam penetrability
Ability of an xray beam to penetrate tissue.
84
Beam restrictor
Device that restricts the size of the xray field to only the anatomical structure of interest.
85
Beam limiting device
Device that provides a means of restricting the size of an x-ray field.
86
Becquerrel (Bq)
Special name for the SI units of radioactivity. One becquerel is equal to disintegration per second.
87
Beta particle
Ionizing radiation with characteristics of an electron; emitted from the nucleus of a radioactive atom.
88
Binary number system
Number system with only two digits, 0 and 1.
89
Bipolar
Magnet that has two poles
90
Bit depth
Number of bits used to reproduce image gray levels (eg., 8 bits=2^8=256 gray levels)
91
Bit
smallest unit of measure in computer storage capacity
92
Body habitus
General size and shape of a patient
93
Brachytherapy
Radiation oncology in which the source of tradition is on or in the body.
94
Bremsstrahlung x-ray
X-rays that results from interaction of the projectile electron with a target nucleus; braking radiation.
95
Brightness gain
Ability of the image intensifier to increase the illumination level of the image.
96
Bucky factor
Ratio of incident radiation to transmitted radiation through a grid; ratio of patient dose with and without a grid.
97
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.
98
Buffer
Acetate added to the fixer to maintain a constant pH
99
Buffering agent
Alkali compound in the developer that enhances the action of the developing agent by controlling the concentration of hydrogen ions.
100
Byte
Group of eight bits; represents one character or digit.
101
Calipers
Instrument with two bent or curved legs used for measuring the thickness of a solid.
102
Calorie
Energy necessary to raise the temperature of 1 g of water by 1 celcius
103
C-arm fluoroscope
Portable device for fluoroscopy. The opposite ends of the C-shaped support arm hold the image intensifier and the xray tube.
104
Cassette
Rigid holder the contains the film and screens.
105
Cassette loaded spot film
conventional method of capturing images with image intensified fluoroscopes.
106
Catabolism
process that creates energy for a cell by breaking down molecular nutrients that are brought to and diffused through the cell membrane.
107
Cathode ray tube
Electron beam tube designed for a two dimensional display of signals
108
Cathode rays
Stream of electrons
109
Cathode
negative side of the x-ray tube; contains the filament and the focusing cup
110
Cell cloning
Process by which normal cells produce a visible colony in a short time.
111
Cell cycle time
Average time from one mitosis to another
112
Cell theory
Principle that all plants and animals contain cells as their basic functional units.
113
Cell
Basic unit of all living matter.
114
Central Axis x ray beam
X-ray beam composed of x-rays that travel along the center of the useful x-ray beam.
115
Central processing unit
Processing hardware in large computers
116
Central ray
Center of the xray beam that interacts with the image receptor
117
Centrifugal force
force that keeps an electron in orbit
118
Characteristic Curve
Graph of optical density versus log relative response; H&D curve.
119
Characteristic x-ray
X-ray released as a result of the photoelectric effect; its discrete energies are determined by the respective electron biding energy.
120
Charge coupled device
Solid state device that converts visible light photons to electrons.
121
Chemical Energy
Energy released by a chemical reaction
122
chemical fog
Artifact produced by chemical contamination of the developer
123
Chemical symbol
Alphabetic abbreviation for an element.
124
Chip
Tiny piece of semiconductor material
125
Classical scattering
Scattering of x-rays with no loss of energy. Also called coherent, Rayleigh, or thompson scattering.
126
Clearing agent
A chemical, usually ammonium thiosulfate, that is added to the fixer to remove undeveloped silver bromine from the emulsion.
127
Collimation
Restriction of the useful x-ray beam to reduce patient size and shape.
128
Commutator
Device that acts like a switch, converting an alternating current generator to a direct current generator.
129
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.
130
Compression device
Device that maintains close screen film contact when the cassette is closed and latched.
131
Compression
The act of flattening soft tissue to improve optical density.
132
Compton effect
Scattering of x-rays that results in ionization and loss of energy.
133
Compton scattering
Interaction between an x-ray and a loosely bound outer-shell electron that results in ionization and x-ray scattering.
134
Computed Radiography
Radiographic technique that uses a photostimulable phosphor as the image receptor and an area beam.
135
Computed tomography
Creation of a cross sectional tomographic section of the body with a rotating fan beam, a detector array, and computed reconstruction.
136
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.
137
Computer aided detection
Use of a highly complex pattern recognition
138
Conduction
Transfer of heat by molecular agitation
139
Conductor
Material that allows heat or electric current to flow
140
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.
141
Cone
Circular metal tube that attaches to x-ray tube housing to limit the beam size and shape.
142
Cones and Cylinders
Modifications of the aperture diaphragm.
143
Connective tissue
Tissue that binds tissue and organs together
144
Contrast Agent
Compound used as an aid for imaging internal organs with x-rays.
145
Contrast improvement factor
Ratio of radiographic contrast with a grid to that without a grid.
146
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.
147
Contrast medium
Agent that enhances differences between anatomical structures.
148
Contrast resolution
Ability to distinguish between and to image similar tissues.
149
Contrast
Degree of difference between the light and dark areas of a radiograph.
150
Convection
Transfer of heat by the movement of hot matter to a colder place.
151
Conversion efficiency
Rate at which x-ray energy is transformed into light in an intensifying screen.
152
Conversion factor
Ratio of illumination intensity at the output phosphor to radiation intensity incident on the input phosphor.
153
Coolidge tube
Type of vacuum tube is use today that allows x-ray intensity and energy to be selected separately and accurately.
154
Cosmic rays
Particulate and electromagnetic radiation emitted by the sun and the stars.
155
Coulomb
SI unit of electric charge
156
Coupling
Joining of magnetic fields produced by the primary and secondary coils.
157
Covalent bond
Chemical union between atoms formed by sharing one or more pairs of electrons.
158
Covering power
The more efficient use of silver in an emulsion to produce the same optical density per unit exposure.
159
Crookes tube
Forerunner of modern fluorescent, neon, and x-ray tubes.
160
Crossed grid
Grid on which lead strips run parallel to the long and short axes.
161
Crossover rack
Device in an automatic processor that transports film from one tank to the next.
162
Cytoplasm
Protoplasm that exists outside the cell's nucleus
163
Cytosineose
Nitrogenous organic base that attaches to a deoxyribose molecule.
164
Decimal system
System of numbers based on multiples of ten
165
Densitometer
Instrument that measures the optical density of exposed film.
166
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.
167
Detail
Degree of sharpness of structural lines on a radiograph.
168
Detective quantum efficiency
Percentage of x-rays absorbed by the image receptor.
169
Detector array
Group of detectors and the interspace material used to separate them; the image receptor in computed tomography.
170
Developing agent
A chemical, usually phenidone, hydroquinone, or Metol that reduces exposed silver ions to atomic silver.
171
Developing
Stage of processing during which the latent image is converted to a manifest image.
172
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.
173
Diaphragm
Device that restricts an x-ray beam to a fixed size.
174
DICOM
Digital Imging and Communications in Medicine---Standard that enables imaging systems from different manufacturers to communicate.
175
Differential absorption
Different degrees of absorption in different tissues that result in image contrast and formation of the xray image.
176
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.
177
Diode
Vacuum tube with two electrodes--a cathode and an anode.
178
Dipolar
Referring to a molecule with areas of opposing electric charge.
179
Direct current
flow of electricity in only one direction within a conductor.
180
Direct effect
Effect of radiation that occurs when ionizing radiation interacts directly with a particularly radiosensitive molecule.
181
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.
182
Direct exposure film
film used without intensifying screens.
183
Distortion
Unequal magnification of different portions of the same object.
184
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.
185
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.
186
Dose Limit
Maximum permissible occupational radiation dose.
187
Dose
Amount of radiant energy absorbed by an irradiated object.
188
Dosimeter
Instrument that detects and measures exposure to ionizing radiation.
189
Dosimetry
The practice of measuring the intensity of radiation.
190
Double contrast examination
Examination of the colon that uses air and barium for contrast.
191
Double emulsion film
Radiographic film that has an emulsion coating on both sides of the base and a layer of supercoat over each emulsion.
192
Double helix
configuration of DNA that is shaped like a ladder twisted about an imaginary axis like a spring.
193
Dynamic range
Range of values that can be displayed by an imaging system; shades of gray.
194
Eddy current
Current that opposes the magnetic field that induced it, creating a loss of transformer efficiency
195
Edge enhancement
Accentuation of the interface between different tissues.
196
Edge response function
Mathematical expression of the ability of the computed tomographic scanner to reproduce a high contrast edge with accuracy.
197
Effective atomic number
Weighted average atomic number for the different elements of a material.
198
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.
199
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.
200
Effective focal spot size
Area projected onto the patient and the image receptor.
201
Electric current
Flow of electrons
202
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.
203
Electrical energy
Work that can be done when an electron or an electronic charge moves through an electric potential.
204
Electricity
form of energy created by the activity of electrons and other subatomic particles in motion.
205
Electrification
Process of adding or removing electrons from a substance.
206
Electrifiation
Process of adding or removing electrons from a substance.
207
Electrified object
Object that has too few or too many electrons.
208
Electrode
Electrical terminal or connector.
209
Electromagnet
Coil or wire wrapped around an iron core that intensifies the magnetic field.
210
Electromagnetic energy
Type of energy in x-rays, radio waves, microwaves, and visible light.
211
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).
212
Electromagnetic spectrum
Continuum of electromagnetic energy.
213
Electromotive force
Electric potential; measured in volts.
214
Electron binding energy
Strength of attachment of an electron to the nucleus.
215
Electron optics
Engineering aspects of maintaining proper electron to the nucleus
216
Electron spin
Momentum of a particle of an atom in a fixed pattern.
217
Electron volt
Unit of energy equal to that which an electron acquires from a potential difference of 1 V.
218
Electron
Elementary particle with one negative charge. Electrons surround the positively charged nucleus and determine the chemical properties of the atom.
219
Electrostatics
Study of fixed or stationary electric charge.
220
Element
Atoms that have the same atomic number and the same chemical properties. Substance that cannot be reduced further without changing its chemical properties.
221
Elemental mass
Characteristic mass of an element, determined by the relative abundance of isotopes and their respective atomic masses.
222
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.
223
Emulsion
Material with which x-rays or light photons from screens interact and transfer information.
224
Endoplasmic reticulum
Channel or series of channels that allows the nucleus to communicate with the cytoplasm.
225
Energy levels
Orbits around the nucleus that contain a designated number of electrons.
226
Energy subtraction
technique that uses the two x-ray beams alternately to provide a subtraction image that results from differences in photoelectric interaction.
227
Energy
Ability to do work; measured in joules.
228
Entrance roller
Roller that grips the film to begin its trip through the processor.
229
Entrance skin exposure
X-ray exposure to the skin; expressed in milliroentgen
230
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.
231
Epithelium
Covering tissue that lines all exposed surfaces of the body, both exterior and interior.
232
Erg (joule)
Unit of energy and work
233
Excitation
Addition of energy to a system achieved by raising the energy of electrons with the use of x-rays.
234
Exit radiation
x-rays that remain after the beam exits through the patient.
235
Exposed matter
Matter that intercepts radiation and absorbs part or all of it; irradiated matter.
236
Exposure factors
Factors that influence and determine the quantity and quality of x-radiation to which the patient is exposed.
237
Exposure linearity
Ability of a radiographic unit to produce a constant radiation output for various combinations of mA and exposure time.
238
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).
239
Extinction time
Time required to end an exposure
240
Extrafocal radiation, off focus radiation
Electrons that bounce off the focal spot and land on other areas of the target.
241
Extrapolation
Estimation of a value beyond the range of known vaues
242
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.
243
Fan beam
X-ray beam pattern used in computed tomography and digital radiography; projected as a slit.
244
Feed tray
The start of the transport system, where the film to be processed is inserted into the automatic processor in the darkroom.
245
Ferromagnetic material
Material that is strongly attracted by a magnet and that usually can be permanently magnetized by exposure to a magnetic field.
246
Field of view
Image matrix size provided by digital x-ray imaging systems.
247
Field
Interactions among different energies, forces, or masses that cannot be seen but can be described mathematically.
248
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.
249
Filament
Part of the cathode that emits electrons, resulting in a tube current.
250
File
Collection of data or information that is treated as a unit by the computer.
251
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.
252
Film graininess
Distribution of silver halide grains in an emulsion.
253
Filtered back projection
Process by which an image acquired during computed tomography and stored in computer memory is reconstructed.
254
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.
255
First generation computed tomographic scanner
Finely collimated x-ray beam, single detector assembly that translates across the patient and rotates between successive translations.
256
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.
257
Fixing
Stage of processing during which the silver halide not exposed to radiation is dissolved and removed from the emulsion.
258
Fluorescence
Emission of visible light only during stimulation
259
Fluorescent screen
Cycle in a television picture tube whereby the electron beam creates the television optical signal and then immediately fades.
260
Fluoroscope
Device used to image moving anatomical structures with x-rays
261
Fluoroscopy
Imaging modality that provides a continuous image of the motion of internal structures while the x-ray tube is energized. Real time imaging.
262
Flux gain
Ratio of the number of light photons at the output phosphor to the number of x-rays at the input phosphor.
263
Focal spot
Region of the anode target in to produce x-rays.which electrons interact
264
Focal spot blur
Blurred region on the radiograph over which the technologist has little control.
265
Focused grid
Radiographic grid constructed so that the grid strips converge on an imaginary line.
266
Focusing cup
Metal shroud that surrounds the filament
267
Fog density
Development of silver grain that contains no useful information.
268
Fog
Unintended optical density on a radiograph that reduces contrast through light or chemical contamination.
269
Force
That which changes the motion of an object; a push or a pull. Expressed in newtons (N).
270
Foreshortening
Reduction in image size; related to the angle of inclination of the object
271
Fourth generator computed tomographic imaging system
Unit in which the x-ray source rotates but the detector assembly does not.
272
Fraction
Numeric value expressed by dividing one number by another.
273
Fractionated
Radiation dose delivered at the same dose in equal portions at regular intervals.
274
Free radical
Uncharged molecule that contains a single unpaired electron in the valence shell.
275
Frequency
Number of cycles or wavelengths of a simle harmonic motion per unit time. Expressed in Hertz (Hz). 1 Hz = 1 cycle/s.
276
Fulcrum
Imaginary pivot point bout which the x-ray tube and the image receptor move.
277
Full width at half maximum
Width of the profile at half its maximum value.
278
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.
279
Fundamental laws of motion
The three principles of inertia, force, and action/reaction established by Isaac Newton.
280
Fundamental particles
The three primary constituents of an atom: electrons, photons, and neutrons.
281
Gantry
Portion of the computed tomographic or magnetic resonance imaging system that accommodates the patient and source or the detector assemblies.
282
Gelatin
Part of the emulsion that provides mechanical support for the silver halide crystals by holding them uniformly dispersed in place.
283
Gonadal dose
Exposure to the reproductive organs
284
Gradient
Slope of the tangent at any point on the characteristic curve.
285
Gray (Gy)
Special name for the SI unit of absorbed dose and air kerma. 1 Gy = 1 J/kg = 100 rad.
286
Gray scale
Image display in which intensity is recorded as variations in brightness.
287
Grid cleanup
Ability of a grid to absorb scatter radiation.
288
Grid cutoff
Absence of optical density on a radiograph caused by unintended x-ray absorption in a grid.
289
Grid frequency
Number of grid lines per inch or centimeter.
290
Grid lines
Series of sections of radiopaque material.
291
Grid ratio
Ratio of grid height to grid strip separation.
292
Grid
Device used to reduce the intensity of scatter radiation in the remnant x-ray beam.
293
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.
294
Guanine
Nitrogenous organic base that attaches to a deoxyribose molecule.
295
Halation
Reflection of screen light transmitted through the emulsion and base.
296
Half-life
Time required for a quantity of radioactivity to be reduced to half its original value.
297
Half-value layer (HVL)
Thickness of absorber necessary to reduce an x-ray beam to half its original intensity.
298
Half wave rectification
Condition in which the voltage is not allowed to swing negatively during the negative half of its cycle.
299
Hard copy
Permanent image on film or paper, as opposed to an image on a cathode ray tube, a disc, or magnetic tape.
300
Hard x-ray
X-ray that has high penetrability and therefore is of high quality.
301
Hardener
A chemical, usually potassium glutaraldehyde alum in the fixer, that is used to stiffen and shrink the emulsion.
302
Hardware
Visible parts of the computer
303
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.
304
Hertz (Hz)
Unit of frequency; the number of cycles or oscillations that occur each second during simple harmonic motion.
305
Hexadecimal number system
Number system used by low level applications to represent a set of four bits.
306
High contrast resolution
Ability to image small objects with high subject contrast; spatial resolution
307
High voltage generator
One of the three principal parts of an x-ray imaging system; it is always close to the x-ray tube.
308
Homeostasis
a. State of equilibrium among tissue and organs. b. Ability of the body to return to normal function despite infection and environmental changes.
309
Hormone
Protein manufactured by various endocrine glands and carried by the blood to regulate body functions such as growth and development.
310
Horsepower
British unit of power
311
Hounsfield unit
Scale of computed tomographic numbers used to assess the nature of tissue.
312
Hypersthenic
Referring to a body habitus of a patient who is large in frame and overweight.
313
Hythenicpo Retention
Undesirable retention of the fixer in emulsion.
314
Hypo
Sodium thiosulfate, a fixing agent that removes unexposed and undeveloped silver halide crystals from the emulsion.
315
Hyposthenic
Referring to a body habitus of a patient who is thin but healthy looking.
316
Hysteresis
Additional resistance created by the alternate reversal of the magnetic field caused by the alternating current.
317
Image detail
Sharpness of small structures on the radiograph
318
Image intensifier
Electronic vacuum tube that amplifies a fluoroscopic image to reduce patient dose.
319
Image matrix
Layout of cells in rows and columns.
320
Image noise
Deterioration of the radiographic image
321
Image receptor
Medium that transforms the x-ray beam into a visible image; radiographic film or a phosphorescent screen.
322
Image receptor contrast
Contrast that is inherent in the film and is influenced by processing of the film.
323
Image forming x-ray
X-ray that exits from the patient and enters the image receptor.
324
Improper fraction
Fraction in which the quotient is greater than 1.
325
Indirect effect
Effect of radiation that results from the production of free radicals produced by the interaction of radiation with water.
326
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.
327
Induction
Process of making ferromagnetic material magnetic.
328
Inertia
Property of matter that resists change in motion or at rest.
329
Infrared light
Light that consists of photons with wavelengths longer than those of visible light but shorter than those of microwaves.
330
Infrared radiation
Electromagnetic radiation just lower in the energy than visible light, with a wavelength in the range of 0.7 to 1000 um
331
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.
332
Initiation time
Time required to start an exposure
333
input
Process of transferring information into primary memory
334
Insulator
Material that inhibits the flow of electrons within a conductor or during heat transfer.
335
Integrate mode
Function of an instrument designed to measure the total accumulated intensity of radiation over time.
336
Intensification Factor
Ratio of exposure without screens to that with screens to produce the same optical density.
337
Intensifying screen
Sensitive phosphor that converts x-rays to light to shorten exposure time and reduce patient dose.
338
Intensity profile
Projection formed by the intensity of radiation detected according to the attenuation pattern.
339
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.
340
Interphase
Period of growth of the cell between divisions
341
Interpolation
Estimation of a value between two known values
342
Interrogation time
Time during which the signal from an image detector is sampled.
343
Interspace material
Sections of radiolucent material in a grid.
344
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.
345
Inverse voltage
Current that flows from the anode to the cathode
346
Inverter
High speed switches that convert direct current into a series of square pulses.
347
Ion chamber
Instrument that detects and measures the radiation intensity in areas outside of protective barriers.
348
Ion pair
Two oppositely charged particles.
349
Ion
Atom with too many or too few electrons; an electrically charged particle.
350
Ionic bond
Bonding that occurs because of an electrostatic force between ions.
351
Ionization potential
Amount of energy (34 eV) necessary to ionize tissue atoms.
352
Ionization
Removal of an orbital electron from an atom.
353
ionized
Referring to an atom that has an extra electron or has had an electron removed.
354
Ionizing radiation
Radiation capable of ionization
355
Irradiated
Referring to matter that intercepts radiation and absorbs part or all of it; exposed.
356
Isobars
Atoms that have the same number of nucleons but different numbers of protons and neutrons.
357
Isochromatid
Fragment in a chromosome aberration.
358
Isomers
Atoms that have the same numbers of protons and neutrons but a different nuclear energy state.
359
Isotones
Atoms that have the same number of neutrons.
360
Isotopes
Atoms that have the same number of protons but a different number of neutrons.
361
Isotropic
Equal intensity in all directions; having the same properties in a directions.
362
Joule (J)
Unit of energy; the work done when a force of 1 N acts on an object along a distance of 1 m.
363
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)
364
Kilo
Prefix meaning "1000"
365
Kilogram
Scientific unit of mass that is unrelated to gravitational effects; 1000g
366
Kilovolt
Electric potential equal to 1000 V.
367
Kilovolt peak
Measure of the maximum electrical potential across an x-ray tube; expressed in kilovolts.
368
Kinetic energy
Energy of motion
369
Latent image center
Sensitivity center that has many silver ions attracted to it.
370
Latent image
Unobservable image stored in the silver halide emulsion; it is made manifest by processing.
371
Latent period
Period after the prodromal stage of the acute radiation syndrome during which no sign of radiation sickness is apparent.
372
Lateral decentering
Improper positioning of the grid that results in cuttoff.
373
Latitude
Range of x-ray exposure over which a radiograph is acceptable
374
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.
375
Law of conservation of matter
Principle that states that matter can be neither created nor destroyed.
376
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.
377
LD 50/60
Dose of radiation expected to cause death within 60 days to 50% of those exposed.
378
Leakage radiation
Secondary radiation emitted through the tube housing
379
Limiting resolution
Spatial frequency at a modulation transfer function equal to 0.1.
380
Line focus principle
Design incorporated into x-ray tube targets to allow a large area for heating while a small focal spot is maintained.
381
Line focus
Projection of an inclined line onto a surface, resulting in a smaller size.
382
Line pair
One bar and its interspace of equal width.
383
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.
384
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.
385
Linear, nonthreshold
Referring to the dose-response relationship that intersects the dose axis at or below zero.
386
Linear, threshold
Referring to the dose-response relationship that intercepts the dose axis at a value greater than zero
387
Log relative exposure (LRE)
change in optical density over each exposure interval.
388
Long gray scale
Low contrast radiograph that has many shades of gray
389
Look-up table
Matrix of data that manipulates the values of gray levels, converting an image input value to a different output value.
390
Low contrast resolution
Ability to image objects with similar subject contrast
391
Luminescence
Emission of visible light
392
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.
393
Lysosome
Cell that contains enzymes capable of digesting cellular fragments.
394
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.
395
Magnetic dipole
Current that flows in an infinitesimally small loop.
396
Magnetic domain
An accumulation of many atomic magnents with their dipoles aligned.
397
Magnetic domain
An accumulation of many atomic magnets with their dipoles aligned.
398
Magnetic permeability
Property of a material that causes it to attract the imaginary lines of the magnetic field.
399
Magnetic Susceptibility
The ease with which a substance can be magnetized.
400
Magnetism
The polarization of a material.
401
Magnetite
The magnetic oxide of iron.
402
Magnetization
Relative magnetic flux density in a materia compared with that in a vacuum.
403
Magnification
Condition in which the images on the radiograph are larger than the object they represent.
404
Magnitude
Number that represents a quantity.
405
Main-chain scission
Breakage of the long chain macromolecule that divides the long, single molecule into smaller ones.
406
Mainframe computer
A fast, medium-to- large-capacity system that has multiple microprocessors.
407
Manifest image
The observable image that is formed when when the latent image undergoes proper chemical processing.
408
Man-made radiation
X-rays and artificially produced radionuclides used for nuclear medicine.
409
Mass density
Quantity of matter per unit volume.
410
Mass
A quantity of matter; expressed in kilograms.
411
Mass energy equivalence
Energy equals mass multiplied by the square of the speed of light.
412
Matrix
Rows and columns of pixels displayed on a digital image.
413
Matter
Anything that occupies space and has form or shape.
414
Maximum permissible dose
Dose of occupational radiation that would be expected to produce no significant radiation effects. An old expression. Replaced by Dose Limit.
415
Mean lethal dose
Constant related to the radio sensitivity of a cell.
416
Mean marrow dose
Average radiation dose to the entire active bone marrow.
417
Mean Survival Time
Average time between exposure and death.
418
Mechanical energy
Ability of an object to do work.
419
Meiosis
Process of germ cell division that reduces the chromosomes in each daughter cell to half the number of chromosomes in the parent cell.
420
Metabolism
Anabolism and catabolism
421
Metaphase
Phase of cell division during which the chromosomes are divisible.
422
Metol
Secondary constituent used in the chemical composition of developing agents.
423
Microcalcifications
Calcific deposits that appear as small grains of varying sizes on the x-ray film
424
Microcomputer
Personal computer or electronic organizer
425
Microcontroller
Tiny computer installed in an appliance.
426
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
427
Milliampere (mA)
Measure of x-ray tube current.
428
Milliampere second (mAs)
Product of exposure time and x-ray tube current; measure of the total number of electrons.
429
Mitochondrion
Structure that digests macromolecules to produce energy for the cell.
430
Mitosis
process of somatic cell division wherein a parent cell divides to form two daughter cells identical to the parent cell.
431
Modem
Device that converts digital information into analog information.
432
Modulation transfer function
Mathematical procedure for measuring resolution
433
Modulation
Changing of the magnitude of a video signal; the magnitude is directly proportional to the light intensity received by the television camera tube.
434
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.
435
Molybdenum
Target material for x-ray tube s that is used in mammography.
436
Momentum
Product of the mass of an object and its velocity.
437
Monoenergetic
Beam that contains x-rays or gama rays that all have the same energy.
438
Monosaccharide
A sugar
439
Motherboard
Main circuit board in a system unit.
440
Motion blur
Blurring of the image that results from movement of the patient or the x-ray tube during exposure.
441
Moving grid
Grid that moves while the x-ray exposure is being made.
442
National Council on Radiation Protection and Measurement
Organization that continuously reviews recommended dose limits.
443
Natural environmental radiation
Naturally occurring ionizing radiation, including cosmic rays, terrestrial radiation, and internally deposited radionuclides.
444
Natural magnet
Magnet that gets its magnetism from the Earth
445
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.
446
Neuron
Cell of the the nervous system that has long, thin extensions from the cell to distant parts of the body.
447
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.
448
Newton (N)
Unit of force in the SI system; 1 N =0.22 lb.
449
Node
One of many stations or terminals of a computer network.
450
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.
451
Nonionizing radiation
Radiation for which the mechanism of action in tissue does not directly ionize atomic or molecular systems through a single interaction.
452
Nonlinear, nonthreshold
Referring to varied responses that are produced from varied doses, with any dose expected to produce a response.
453
Nonlinear, threshold
Referring to varied responses that are produced from varied doses, with a particular level below which there is no response.
454
Nonstochastic effects
Biologic effects of ionizing radiation that demonstrate the existence of a threshold. Severity of biologic damage increases with increased dose.
455
North pole
Magnetic pole that has a positive electrostatic charge.
456
Nuclear Energy
Energy contained within the nucleus of an atom.
457
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.
458
Nucleon
A proton or a neutron.
459
Nucleotide
Unit formed from a nitrogenous base, a five carbon sugar molecule, and a phosphate molecule.
460
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.
461
Nuclide
General term that refers to all known isotopes, both stable and unstable, of chemical elements.
462
Object plane
Plane in which the anatomical structures that are to be imaged lie.
463
Object to image receptor distance
Distance from the image receptor to the object that is to be imaged.
464
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.
465
Occupational exposure
Radiation exposure received by radiation workers.
466
Off focus radiation
X-rays produced in the anode but not at the focal spot.
467
Off level grid
Artifact produced by an improperly positioned radiographic tube not by an improperly positioned grid.
468
Oocytes
Primordial follicles that grow to encapsulate oogonia.
469
Opaque
Surface that does not allow the passage of light.
470
Open filament
Condition that results when the filament becomes thinner and breaks.
471
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.
472
Operating system
Series of instructions that organizes the course of data through the computer to solve a particular problem.
473
Optical density
Degree of blackening of a radiograph.
474
Optical disc
Removable disc that uses laser technology to write and read data.
475
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.
476
Organ system
Combination of tissues and organs that forms an overall integrated organization.
477
Organic molecule
Molecule that is life supporting and contains carbon.
478
Organs
Collection of tissues of similar structure and function.
479
Origin
Point at which two axes meet on a graph.
480
Orthochromatic
Referring to blue or green sensitive film; usually exposed with rare Earth screen.
481
Outcome analysis
Image interpretation that involves reconciling the patient's ultimate disease condition with the radiologist's diagnosis.
482
Output
Process of transferring the results of a computation from primary memory to storage or to the user.
483
Overcoat
Protective covering of gelatin that encloses the emulsion.
484
Overexposed
Referring to a radiograph that is too dark because too much x-radiation reached the image receptor.
485
Oxidation
Reaction that reduces an electron
486
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.
487
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.
488
Panchromatic
Referring to film that is sensitive to the entire visible light spectrum.
489
Parallel circuit
Circuit that contains elements that bridge conductors rather than lie in a line along a conductor.
490
Parallel grid
Simple grid in which all lead grid strips are parallel.
491
Paramagnetic
Referring to materials slightly attracted to a magnet and loosely influenced by an external magnetic field.
492
Parenchymal
Referring to part of the organ that contains tissues representative of that particular organ.
493
Partial volume effect
Distortion of signal intensity from a tissue because it extends partially into an adjacent slice thickness.
494
Particle accelerator
An atom "smasher." Cyclotron. Linear Accelerator.
495
Particulate radiation
Radiation distinct from x-rays and gamma rays; examples include alpha particles, electrons, neutrons, and protons.
496
Penetrability
Ability of an x-ray to penetrate tissue; range in tissue; x-ray quality.
497
Penetrometer
Aluminum step wedge
498
Penumbra
Image blur that results from the size of the focal spot; geometric unsharpness.
499
Permanent magnent
Magnet whose magnetism is induced artificially
500
Phantom
Device that simulates some parameters of the human body for evaluation of imaging system performance.
501
Phenidone
Secondary constituent in the chemical composition of developing agents.
502
Phosphor
Active layer of the radiographic intensifying screen closest to the radiographic film.
503
Phosphorescence
Emission of visible light during and after stimulation
504
Photoconductor
Material that conducts electrons when illuminated.
505
Photoconductor
Material that conducts electrons when illuminated.
506
Photodiode
Solid state device that converts light into an electric current.
507
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.
508
Photoelectric effect
Absorption of an x-ray by ionization
509
photoelectron
Electron that has been removed during the process of photelectric absorption.
510
Photoemission
Electron emission after light stimulation.
511
Photographic effect
formation of the latent image.
512
Photometer
Instrument that measures light intensity.
513
Photomultiplier tube
Electron tube that converts visible light into an electrical signal.
514
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.
515
Photospot camera
Camera that exposes only one frame when active, receiving its image from the output phosphor of the image intenbsifier tube.
516
Photostimulation
Emission of visible light after excitation by laser light.
517
Photothermographic
Printing process by which film is exposed to light, thereby forming a latent image that is made visible by heat.
518
Phototimer
Device that allows automatic exposure control.
519
Pixel
Picture element; the cell of a digital image matrix.
520
Planck's constant
Fundamental physical constant that relates the energy of radiation to its frequency.
521
Planetary rollers
Rollers positioned outside the master roller and guide shoes.
522
Pluripotential stem cell
Stem cell that has the ability to develop into several differnt types of mature cells.
523
Pocket ionization chamber (Pocket dosimeter)
Personnel radiation monitoring device.
524
Point lesion
Any change that results in impairment or loss of function at the point of a single chemical bond.
525
Point mutation
Molecular lesion caused by the change or loss of a base that destroys the triplet code and may not be reversible.
526
Polarity
Existence of opposing negative and positive charges.
527
Pole
Magnetically charged end of a material.
528
Polyenergetic
Referring to radiation, such as x-rays with a spectrum of energies.
529
Polysaccharide
Large carbohydrate that includes starches and glycogen.
530
Positive beam limiting (PBL)
Feature of radiographic collimators that automatically adjusts the radiation field to the size of the image receptor.
531
Potassium bromide
Compound used as a restrainer in the developer.
532
Potassium iodide
Compound used as a restrainer in the developer
533
Potential energy
Ability to do work by virtue of position
534
Power
Time rate at which work (w) is done. 1 W = 1 J/s.
535
Precursor cell
An immature cell.
536
Predetector collimator
Collimator that restricts the x-ray beam viewed by the detector array.
537
Prepatient collimator
Collimator that consists of several sections so that a nearly parallel x-ray beam results.
538
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.
539
Preservative
Chemical additive, usually sodium sulfide, which maintains the chemical balance of the developer and fixer.
540
Preventive maintenance
Planned program of parts replacement at regular intervals.
541
Primary coil
The first coildd through which the varying current in an electromagnet is passed.
542
Primary protective barrier
Any wall to which the useful beam can be directed.
543
Processing
Chemical treatment of the emulsion of a radiographic film to change a latent image to a manifest image.
544
Processor
Electronic circuitry that does the actual computations and the memory that supports it.
545
Prodromal period
First stage of the acute radiation syndrom; occurs within hours after radiation exposure.
546
Prone
Having the front or ventral surface downward. Lying flat or prostrate.
547
Proper fraction
Fraction in which the quotient is less than 1.
548
Prophase
Phase of cell division during which the nucleus and the chromosomes enlarge and the DNA begins to take structural form.
549
Proportion
The relation of one part to another.
550
Proportional counter
Sensitive instrument that is used primarily as stationary laboratory instrument for the assay of small quantities of radioactivity.
551
Protective coating
Layer of the radiographic intensifying screen closest to the radiographic film.
552
Protective housing
Lead lined metal container into which the x-ray tube is fitted.
553
Protein synthesis
Metabolic production of proteins
554
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.
555
Protracted dose
Dose of radiation that is delivered continuously bu at a lower dose rate.
556
Pulse mode/rate mode
Instruments designed to detect the p resence of radiation.
557
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.
558
Quality Control
All actions necessary to control and verify the performance of equipment; part of quality assurance.
559
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.
560
Quantum theory
Theory in the physics of matter smaller than an atom and of electromagnetic radiation.
561
Quantum
An x-ray photon
562
Rad (radiation absorbed dose)
Special unit for absorbed dose and air kerma. 1 rad =100 erg/g= 0.01 Gy.
563
Radiation (thermal)
Transfer of heat by the emission of infrared electromagnetic radiation.
564
Radiation biology
Branch of biology that is concerned with the effects of ionizing radiation on living systems.
565
Radiation exposure
X-ray quantity or intensity; measured in roentgens.
566
Radiation fog
Artifact caused by unintentional exposure to radiation.
567
Radiation hormesis
Theory that suggest that very low radiation doses may be beneficial.
568
Radiation quality
Relative penetrability of an x-ray beam determined by its average energy; usually measured by half value layer or kilovolt peak.
569
Radiation quantity
Intensity of radiation; usually measured in milliroentgen
570
Radiation safety officer
That individual physician, medical physicist, or technologist assigned to develop and implement the radiation safety program.
571
Radiation standards
Recommendations, rules, and regulations regarding permissible concentrations, as well as safe handling techniques, transportation, and industrial control of radioactive material.
572
Radiation weighting factor
Factor used for radiation protection that accounts for differences in biologic effectiveness between different radiations Formerly called quality factor.
573
Radiation
Energy emitted and transferred through matter.
574
Radioactive decay
Naturally occurring process whereby an unstable atomic nucleus relieves its instaility through the emission of one or more energetic particles.
575
Rad (radiation absorbed dose)
Special unit for absorbed dose and air kerma. 1 rad =100 erg/g= 0.01 Gy.
576
Radiation (thermal)
Transfer of heat by the emission of infrared electromagnetic radiation.
577
Radiation biology
Branch of biology that is concerned with the effects of ionizing radiation on living systems.
578
Radiation exposure
X-ray quantity or intensity; measured in roentgens.
579
Radiation fog
Artifact caused by unintentional exposure to radiation.
580
Radiation hormesis
Theory that suggest that very low radiation doses may be beneficial.
581
Radiation quality
Relative penetrability of an x-ray beam determined by its average energy; usually measured by half value layer or kilovolt peak.
582
Radiation quantity
Intensity of radiation; usually measured in milliroentgen
583
Radiation safety officer
That individual physician, medical physicist, or technologist assigned to develop and implement the radiation safety program.
584
Radiation standards
Recommendations, rules, and regulations regarding permissible concentrations, as well as safe handling techniques, transportation, and industrial control of radioactive material.
585
Radiation weighting factor
Factor used for radiation protection that accounts for differences in biologic effectiveness between different radiations Formerly called quality factor.
586
Radiation
Energy emitted and transferred through matter.
587
Radioactive decay
Naturally occurring process whereby an unstable atomic nucleus relieves its instability through the emission of one or more energetic particles.
588
Radioactive disintegration
Process by which the nucleus spontaneously emits particles and energy and transforms itself into another atom to reach stability.
589
Radioactive half life
Time required for a radioisotope to decay to half its original activity.
590
Radioactivity
Rate of decay or disintegration of radioactive material. Expressed in curie or becquerel.
591
Radiolysis of water
Dissociation of water into other molecular products as a result of irradiation.
592
Radiographer
Radiologic technologist who deals specifically with x-ray imaging.
593
Radiographic contrast
Combined result of image receptor contrast and subject contrast.
594
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.
595
Radiographic noise
Undesirable fluctuation in the optical density of the image.
596
Radiographic technique chart
Guide that describes standard methods for consistently producing high quality images.
597
Radiographic technique
Combination of settings selected on the control panel of the x-ray imaging system to produce a quality image on the radiograph.
598
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.
599
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.
600
Radiological Society of North America (RSNA)
Scientific society of radiologists and medical physicists.
601
Radiolucent
Referring to a tissue or material that transmits x-rays and appears dark on a radiograph.
602
Radiolysis of water
Dissociation of water into other molecular products as a result of irradiation.
603
Radiolucent
Referring to a tissue or material that transmits x-rays and appears bright on a radiograph.
604
Radionuclides
Any nucleus that emits radiation.
605
Radiopaque
Referring to a tissue or material that absorbs x-rays and appears bright on a radiograph.
606
Radiosensitivity
Relative susceptibility of cells, tissues, and organs to the harmful action of ionizing radiation.
607
Radon
Colorless, odorless, naturally occurring radioactive gas that decays via alpha emission and has a half life of 3.8.
608
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.
609
Rare Earth Element
Element that is a transitional metal found in low abundance in nature.
610
Rare Earth screen
Radiographic intensifying screen made from rare Earth elements, which make it more useful for radiographic imaging.
611
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.
612
Ratio
Mathematical relationship between similar quantities
613
Read only memory
Data storage device that contains information supplied by the manufacturer that cannot be written on or erased.
614
Real time
Display for which the image is continuously renewed, often to view anatomical motion, in fluoroscopy and ultrasound.
615
Reciprocity law
Principle that states that optical density on a radiograph is proportional only to the total energy imparted to the radiographic film.
616
Reconstruction time
Time needed for the compujter to present a digital image after an examination has been completed.
617
Reconstruction
creation of an image from data.
618
Recorded detail
Degree of sharpness of structural lines on a radiograph.
619
Recovery
Repair and repopulation.
620
Rectification
Process of converting alternating current to direct current.
621
Rectifier
Electronic device that allows current flow in only one direction.
622
Red filter
Filter that transmits light only above 600 nm; it is used with both green and blue senstive film
623
Reducing agent
chemical responsible for reduction.
624
Reduction
Process by which an electron is given up by a chemical to neutralize a positive ion.
625
Reflection
Return or reentry of an x-ray.
626
Reflection
Return or reentry of an x-ray.
627
Refective layer
Layer of the intensifying screen that intercepts light headed in other directions and redirects it to the film.
628
Refraction
Deviation of course that occurs when photons of visible light traveling in straight lines pass from one transparent medium to another.
629
Region of interest (ROI)
Area of an anatomical structure on a reconstructed digital image as defined by the operator using a cursor.
630
Relative age-response relationship
Increased incidence of a disease proportional to its natural incidence.
631
Relative age response relationship
Increased incidence of a disease proportional to its natural incidence.
632
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.
633
Relative risk
Estimation of late radiation effects in large populations without precise knowledge of their radiation dose.
634
Relay
Electrical device based on electromagnetic induction that serves as a switch.
635
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.
636
Remnant radiation
X-rays that ass through the patient and interact with the image receptor.
637
Replenishment
Replacement of developer and of fixer in the automatic processing of film.
638
Resistance
Opposition to a force.
639
Resolution
Measure of the ability of a system to image two separate objects and visually distinguish one from the other.
640
Restrainer
Compound that restricts the action of the developing agent to only irradiated silver halide crystals.
641
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.
642
Ribosomes
the site of protein synthesis
643
right hand rule
Rule by which the direction of magnetic field lines can be determined.
644
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.
645
Rotor
Rotating part of an electromagnetic induction motor that is located inside the glass envelope.
646
Secondary protective barrier
Barrier designed to shield an area from secondary radiation.
647
Sagittal plane
Any anterior posterior plane parallel to the long axis of the body.
648
Saturation current
filament current that has risen to its maximum value because all available electrons have been used.
649
Scalar
referring to a quantity or a measurement that has only magnitude.
650
Scatter Radiation
X-rays scattered back in the direction of the incident x-ray beam.
651
Scintillation detector
Instrument used in the detector arrays of many computed tomographic scanners.
652
Screen lag
The phosphorescence in an intensifying screen.
653
Screen speed
Relative number used to identify the efficiency of conversion of x-rays into usable light.
654
Screen film
The most commonly used film; used with intensifying screens.
655
Secondary coil
coil in which induced current in an electromagnet flows
656
Secondary electron
Electron ejected from the outer shell of an atom
657
Secondary memory
Data stored on tape drives, diskettes, and hard disc drives.
658
Secondary protective barrier
Barrier designed to shield an area from secondary radation.
659
Secondary radiation
leakage and scatter reaction
660
Zonography
Thick slice tomography with a tomographic angle of less than 10 degrees`
661
Y-axis
Vertical line of a graph
662
x-ray
Penetrating, ionizing electromagnetic radiation that has a wavelength much shorter than that of visible light.
663
x-ray tube rating charts
Charts that guide the technologist in the use of xray tubes.
664
x-ray quantity
Output intensity of an x-ray imaging system; measured in roentgens (r).
665
x-ray quality
Penetrability of an x-ray beam.
