Intro Flashcards

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1
Q

Refers to imaging in which the energy source is outside the body

A

Transmission imaging

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2
Q

Refers to each point on the image corresponds to information along a straight line trajectory thru the patient

A

Projection imaging

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3
Q

Mammography system in which the xray tube (in some cases the detector) moves in an arc from approximately 7 to 40 degrees around the breast

A

Tomosynthesis

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4
Q

Tomography means

A

Picture (graph)

Slice (tomo)

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5
Q

MRI is approximately _____ times stronger than the earth’s magnetic field

A

10,000 to 60,000 times stronger

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6
Q

Nuclear medicine produces ______ images, because the radioisotopes emit their energy from inside the patient

A

Emission

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7
Q

2D maps of 3D radioisotope distribution and are helpful in evaluation of a large number of disorders

A

Planar nuclear images

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8
Q

Roentgen discovered xray in year

A

1895

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9
Q

Refers to continuous acquisition of a sequence of xray images over time, essentially a real time xray movie of a patient

A

Fluoroscopy

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10
Q

_____ energy xrays are used to reduce conspicuity of the ribs and other bones to permit better visualization of air spaces and soft tissue structures in the thorax

A

High energy xrays

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11
Q

Dark areas (high film optical density) correspond to ____ attenuation

A

Low

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12
Q

Bright areas (low film optical density) correspond to _____ attenuation

A

High

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13
Q

First imaging modality made possible by the computer

A

Computed tomography

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14
Q

Produced by passing xrays thru the body at a large number of angles, by rotating the xray tube around the body

A

CT

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15
Q

Modern CT scanners can acquire _____ mm-thick tomographic images along a ___ cm length of patient in ____ seconds

A

0.50 - 0.62 mm
50 cm
5 seconds

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16
Q

In MRI, proton has a magnetic moment, and when placed in a 1.5 T magnetic field, proton ______ (wobbles) about its axis, and preferentially absorbs radio wave energy at the resonance frequency of about ___ million cycles per second

A

Precesses

64 million

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17
Q

In MRI, Pulse of radio waves is generated by _____ positioned around the patient

A

Antennas/coils

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18
Q

By slightly changing the strength of the magnetic field as a function of position in the patient using magnetic field gradients, the proton resonancr frequency varies as a function of position, since frequency is _______ to magnetic field strength

A

Proportional

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19
Q

An area of MR data collection that allows for analysis of metabolic products in the tissue is _____, whereby a single voxel or multiple voxels may be analyzed using specialized MRI sequences

A

MR spectroscopy

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20
Q

Tomographic counterpart of nuclear medicine planar imaging

A

Single photon emission computed tomography

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21
Q

Positively charged electrons

A

Positrons

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22
Q

Similar to gamma rat emission, except that 2 photons are produced, and they are emitted simultaneously in almost exactly opposite directions

A

Annihilation radiation

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23
Q

Ultilizes rings of detectors that surround the patient, and has special circuitry that is capable of identifying the photon pairs produced during annihilation

A

Positron emission tomography

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24
Q

More sensitive to the presence of radioisotopes than SPECT cameras

A

PET detector system

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25
Q

Contrast in _____ imaging depends upon the tissues ability to concentrate the radioactive material

A

Nuclear imaging

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26
Q

Contrast in ____ imaging is related primarily to the proton density and to relaxation phenomena

A

MRI

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27
Q

Contrast in ______ imaging is largely determined by the acoustic properties of the tissues being imaged, the difference between acoustic impedances

A

Ultrasound

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28
Q

Imaging that shows the amplitude and direction of blood flow by analyzing the frequency shift in the reflected signal and thus motion is the source of contrast

A

Doppler ultrasound

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29
Q

Ability to see small detail

A

Spatial resolution

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30
Q

Size of the smallest object that an imaging system can resolve

A

Limiting spatial resolution

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31
Q

Highest resolution modality

A

Mammography

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32
Q

At 3.5 mHz, the wavelength of sound in soft tissue is about

A

500 um

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33
Q

At 10 Mhz, the wavelength is

A

150 um

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34
Q

Energy that travels thru space or matter

A

Radiation

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35
Q

No mass, unaffected by either electric or magnetic fields, and has a constant speed in a given medium. It does not require matter to propagate

A

Electromagnetic radiation

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36
Q

Interaction of EM radiation can occur by

A

Scattering
Absorption
Transformation

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37
Q

EM radiation is commonly characterized by

A

Wavelength, frequency, energy per photon

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38
Q

Emitted by the nuclei of radioactive atoms

A

Gamma rays

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39
Q

Produced outside the nuclei of atoms. Used in radiography, fluoroscopy and CT

A

Xrays

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40
Q

Produced when xrays or gamma rays interact with various scintillators in the detectors used in several imaging modalities and is also used to display images

A

Visible light

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41
Q

There are two correct ways pf describing EM radiation, as ____ and as discrete particle-like packers or quanta of energy called ______

A

Waves and photon

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42
Q

“Billiard-ball” type of collision between an xray photon and an orbital electron during a _______ scattering event

A

Compton

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43
Q

Xrays photon’s energy is completely absorbed by, and results in the ejection of an orbital electron (a photoelectron), in the _______ effect

A

Photoelectric effect

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44
Q

Intensity of the wave

A

Amplitude

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45
Q

Distance between any two identical points on adjacent cycles

A

Wavelength

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46
Q

Time required to complete one cycle of a wave

A

Period

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47
Q

Number of periods that occur per second is the

A

Frequency

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48
Q

Temporal shift of one wave with respect to the other

A

Phase

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49
Q

Because the speed of EM radiation is constant in a given medium, its frequency and wavelength are ______ proportional

A

Inversely

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50
Q

Wavelengths of xrays and gamma rays are typically measured in fractions of

A

Nanometers

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51
Q

Frequency is expressed in

A

Hertz (Hz)

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52
Q

Planck’s constant represents the

A

Energy of a photon

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53
Q

Energies of photons are commonly expressed in

A

Electron volts

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54
Q

Defined as the energy acquired by an electron as it traverses an electrical potential difference (voltage) of one volt in a vacuum

A

One electron volt

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55
Q

An atom or molecule that has lost or gained one or more electrons has a net electrical charge and is called

A

Ion

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56
Q

Photons of higher frequency than the far UV region of the spectrum (wavelengths greater than 200nm) have sufficient energy per photon to remove bound electrons from atomic shells, thereby producing ionized atoms and molecules. Radiation in this portion of the spectrum is called

A

Ionizing radiation

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57
Q

Minimum energies necessary to remove an electron

A

Ionization energy

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58
Q

Electrons emitted by the nuclei of radioactive atoms are referred to as

A

Beta particles

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59
Q

Negatively charge beta-minus particles or

A

Negatrons

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60
Q

Positively charge electrons, referred to as

A

Beta-plus particles or positrons

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61
Q

An uncharged nuclear particle that has a mass slightly greater than that of a proton. They are released by nuclear fission and are used for radionuclide production

A

Neutrons

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62
Q

Consists of 2 protons and 2 neutrons, it has +2 charge and is identical to the nucleus of a helium atom

A

Alpha particle

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63
Q

Emitted by many high atomic number radioactive elements such as uranium, thorium and radium

A

Alpha particles

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64
Q

The smallest division of an element in which the chemical identity of the element is maintained

A

Atom

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65
Q

The outer electron shell of an atom called _______, Determines the chemical properties of the element

A

Valence shell

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66
Q

Energy required to remove an orbital electron completely from the atom is called its

A

Orbital binding energy

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67
Q

Emissions from transitions exceeding ____ eV are called characteristic or fluorescent xray

A

100

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68
Q

An electron cascade does not always result in the production of a characteristic xray or xrays. A competing process that predominates in low Z elements is

A

Auger electron emision

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69
Q

The probability that the electron transition will result in the emission of a characteristic xray is called

A

Fluorescent yield

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70
Q

Number of protons in nucleus

A

Atomic number (Z)

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71
Q

Total number of protons and neutrons within the nucleus is the

A

Mass number (A)

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72
Q

Excited states that exist longer than 10-12 s are referred to as

A

Metastable or isomeric states

73
Q

Species of atoms characterized by the number of protns and neutrons and the energy content of the atomic nuclei are called

A

Nuclides

74
Q

Number of protons

A

Isotopes

75
Q

Same atomic mass number

A

Isobars

76
Q

Same number of neutrons

A

Isotones

77
Q

Different nuclear energy states

A

Isomer

78
Q

EM radiation emitted from the nucleus as the excited state transitions to a lower (more stable) energy state is called

A

Gamma ray

79
Q

An alternative form of de-excitation is______, in which the de-excitation energy is completely transferred to an orbital electron

A

Internal conversion

80
Q

Energy required to separate an atom into its constituent parts is the

A

Atomic binding energy

81
Q

Sum of the orbital electron binding energy and the nuclear binding energy

A

Atomic binding energy

82
Q

The energy necessary to disassociate a nucleus into its constituent parts and is the result of the strong forces acting between the nucleons

A

Nuclear binding energy

83
Q

The binding energy can be calculated by subtracting the mass of the atom from the total mass of its constituent protons, neutrons and electrons; this mass difference is called the

A

Mass defect

84
Q

During nuclear _______, a nucleus with a large atomic mass splits into two usually unequal parts called fission fragments, each with an average binding energy per nucleon greater than that pf the original nucleus

A

Fission fragments

85
Q

Examples of heavy charged particles

A

Alpha particles and protons

86
Q

Examples of lighter charged particles

A

Electrons and positrons

87
Q

Particles of ionizing radiation include charged particles and uncharged particles such as

A

Charged particles such as Alpha particles, protons, beta particles, positrons, energetic extranuclear electrons

And uncharged particles such as neutrons

88
Q

Refer to coulombic forces exerted on charged particles when they pass in proximity to the electric field generated by the atom’s electron and protons

A

Interactional or collisional losses

89
Q

Energetic charged particles interact with matter by electrical forces and lose kinetic energy via

A

Excitation, ionization and radiative losses

90
Q

Transfer of some of the incident particles energy to electrons in the absorbing material, promotung them to electron orbits farther from the nucleus

A

Excitation

91
Q

In _______, the energy transferred to an electron does not exceed its binding energy

A

Excitation

92
Q

If the transferred energy exceeds the binding energy of the electron, ________ occurs, whereby the electron is ejected electron and the positively charged atom

A

Ionization

93
Q

An ion pair consists of

A

Ejected electron and positively charged atom

94
Q

Ejected electrons posses sufficient energy to produce further ionizations called secondary ionization. These electrons are called

A

Delta rays

95
Q

70% of the energy deposition of energetic electrons in soft tissue occurs via

A

Ionization

96
Q

Average number of primary and secondary ion pairs produced per unit length of the charged particle’s path is called ________ expressed in ion pairs

A

Specific ionization

97
Q

As the alpha particle slows, the specific ionization increases to a maximum called, ______ beyond which it decreases rapidly as the alpha particle acquires electrons and becomes electrically neutral, thus losing its capacity for further ionization

A

Bragg peaks

98
Q

Electrons follow tortuous paths in matter as the result of multiple scattering events caused by ______

A

Coulombic deflections (repulsion and/or attraction

99
Q

Electron particle track follows a

A

Tortuous path due to coulombic deflections

100
Q

Charged particles follow a ______

A

Linear ionization track

101
Q

Distance the particle travels

A

Path length

102
Q

Defined as the depth of penetration of the particle in matter

A

Range

103
Q

The path length of the _______ almost always exceeds its range

A

Electron

104
Q

The path length and range of ______ is nearly equal

A

Charged particles

105
Q

Measure of the average amount of energy deposited locally (near the incident particle track) in the absorber per unit path length

A

Linear energy transfer

106
Q

Reflects all energy losses that occurs before an ion pair is produced

A

Specific ionization

107
Q

Linear energy transfer of a charged particle is proportional to the square of the charge and _______ proportional to the particle kinetic energy

A

Inversely proportional

108
Q

Alpha particles and protons have high/low LET radiation

A

High

109
Q

Low LET radiation includes

A

Energetic electrons and ionizing electromagnetic radiation (gamma rays and xrays)

110
Q

Interaction that deflects a particle or photon from its original trajectory

A

Scattering

111
Q

A scattering event in which the total kinetic energy of the colliding particles is unchanged is called

A

Elastic

112
Q

When scattering occurs with a loss of kinetic energy, the interaction is said to be

A

Inelastic

113
Q

Radiation emission accompanying electron deceleration

A

Braking radiation or bremsstrahlung

114
Q

Total bremsstrahlung emission per atom is ________ to Z2, where Z is the atomic number of the absorber and _______ proportional to the squatr of the mass of the incident particle that i Z2/M2

A

Proportional to Z2

Inversely proportional to square of mass

115
Q

Responsible for the majority of the xrays produced by xray tubes

A

Radiative energy loss

116
Q

These particles cannot cause excitation and ionization via coulombic interactions but can interact with atomic nuclei, sometimes liberating charged particles or nuclear fragments that can directly cause excitation and ionization

A

Neutrons

117
Q

Xray and gamma ray major interactions with matter include

A

Rayleigh scattering
Compton scattering
Photoelectric absorption
Pair production

118
Q

In _____ scattering, the incident photon interacts with and excites the total atom

A

Rayleigh

119
Q

This interaction occurs mainly with very low energy xrays such as those used in mammography

A

Rayleigh scattering

120
Q

In this interaction, electrons are not ejected and thus, ionization does not occur

A

Rayleigh

121
Q

Also referred to as coherent or classical scattering

A

Rayleigh

122
Q

Also called inelastic or nonclassical scattering, it is the predominant interaction of xray and gamma ray photons in the diagnostic energy range with soft tissue

A

Compton scattering

123
Q

Results in the ionization of the at and a division of the incident photon’s energy between the scattered photon and the ejected electron

A

Compton scattering

124
Q

In _______ effect, all of the incident photon energy is transferred to an electron, which is ejected from the atom

A

Photoelectric

125
Q

Primary mode of interaction of diagnostic xrays with image receptors, radiographic contrast materials and radiation shielding, all of which have much higher atomic numbers than soft tissue

A

Photoelectric absorption

126
Q

In ______, an xray or gamma ray interacts with the electric field of the nucleus of an atom. The photon’s energy is transformed into an electron-positron pair

A

Pair production

127
Q

Removal of photons from a beam of xrays or gamma rays as it passes thru matter

A

Attenuation

128
Q

At low photon energies (less than 26 keV), the ________ effect dominates the attenuation processes in soft tissue

A

Photoelectric

129
Q

The fraction of photons removed from a monoenergetic beam of xrays or gamma rays per unit thickness of material is called

A

Linear attenuation coefficient

130
Q

The probability of interaction is proportional to the

A

Number of atoms per volume

131
Q

Defined as thickness of material required to reduce the intensity of an xray or gamma ray beam to one half of its initial value

A

Half value layer

132
Q

Thickness of material that is necessary to reduce the intensity of the beam to a tenth of its initial value. It is often used in xray room shielding design calculations

A

Tenth-value layer

133
Q

Xray beams in radiology are _______, meaning that they are composed of a spectrum of xray energies

A

Polyenergetic

134
Q

It is a way of characterizing the penetrability of the xray beam

A

Half value layer

135
Q

An estimate of the penetration power of the xray beam, expressed as the energy of a monoenergetic beam that would exhibit the same “effective” penetrability

A

Effective energy

136
Q

Shift of xray spectrum to higher effective energies as the beam transverses matter is called

A

Beam hardening

137
Q

Number of photons or particles passing thru a unit cross-sectional area is referred to as the

A

Fluence

138
Q

The fluence rate is called the _____. It is useful in situations in which the photon beam is on for extended periods of time such as in fluoroscopy

A

Flux

139
Q

Amount of energy passing through a unit cross-sectional area is referred to as the

A

Energy fluence

140
Q

It is an acronym for kinetic energy released in matter

A

Kerma

141
Q

SI unit for Kerma

A

Joule per kilogram

Gray (Gy)

142
Q

Mass attenuation coefficient multiplied by the fraction of the energy pf the interacting photons that is transferred to charged particles as kinetic energy

A

Mass energy transfer coefficient

143
Q

Energy imparted by ionizing radiation per unit mass of irradiated material

A

Absorbed dose

144
Q

Kerma is defined using ______ coefficient, whereas dose is defined using ______ coefficient

A

Mass energy transfer-kerma

Mass energy absorption-dose

145
Q

Amount of electrical charge (Q) produced by ionizing electromagnetic radiation per mass is called

A

Exposure

146
Q

Total amount of energy deposited in matter.

Product of dose and the mass over which the energy is imparted.

A

Imparted energy

147
Q

Product of absorbed dose and radiation weighing factor is the

A

Equivalent dose

148
Q

Traditional unit for both dose equivalent and the equivalent dose is the

A

Rem

149
Q

A sievert is equal to ____ rem

A

100

150
Q

Amount of ionization per mass of air due to xrays and gamma rays

A

Exposure

151
Q

Amount of energy imparted by radiation per mass

A

Absorbed dose

152
Q

Kinetic energy transfered to charged particles per unit mass

A

Kerma

153
Q

Kinetic energy transferred to charged particles per unit mass of air

A

Air kerma

154
Q

Total radiation energy imparted to matter

A

Imparted energy

155
Q

A measure of absorbed dose weighted for the biological effectiveness of the type of radiation (relative to low LET photons and electrons) to produce stochastic health effects in humans

A

Equivalent dose

156
Q

A measure of dose equivalent, weighted for the biological sensitivity of the exposed tissues and organs (relative to whole body exposure) to stochastic health effects in humans

A

Effective dose equivalent

157
Q

A measure of equivalent dose, weighted for the biological sensitivity of the exposed tissues and organs (relative to whole body exposure) to stochastic health effects in humans

A

Effective dose

158
Q

Describes the level of detail that can be seen on an image

A

Spatial resolution

159
Q

Most basic measure of the resolution properties of an imaging system

A

Point spread function

160
Q

An imaging system with the same PSF at all locations in the field of view is called

A

Stationary or shift invariant

161
Q

PSFs that vary depending on the position in the field of view is called

A

Nonstationary

162
Q

Describes the extent of blurring that is introduced by an imaging system

A

Point spread function

163
Q

This is particularly useful when the spatial distribution characteristics of glare or scatter phenomenon are the subject of interest

A

Edge spread function

164
Q

An integral calculus procedure that accurately describes mathematically what the blurring process does physically. It is also an important mathematical component of image reconstruction

A

Convolution

165
Q

An algorithm that decomposes a spatial or time domain signal into a series of sine waves that when summed, replicate that signal

A

Fourier transform

166
Q

Once a spatial domain signal is fourier transformed, the resulting data are considered to be in the

A

Frequency domain

167
Q

Sets the upper bound on the spatial frequency that can be detected for a digital detector system with detector pitch

A

Nyquist frequency

168
Q

Ability to detect very subtle changes in gray scale and distinguish them from the noise in the image

A

Contrast resolution

169
Q

Relates more to anatomical structures that produce small changes in signal intensity (image grayscale)

A

Contrast resolutiom

170
Q

Relates to how close one gets tl the truth

A

Accuracy

171
Q

Description of the variation, scatter or reproducibility in a measurement

A

Precision

172
Q

In medical imaging, it has to do with amount of noise in the image

A

Precision

173
Q

Observed darkness

A

Optical density

174
Q

Electronic noise can be from

A

Thermal noise, shot noise

175
Q

Any number of particles or objects than can be counted such as electrons, xray photons, optical photons or even brush strokes on impressionist paintings

A

Quanta

176
Q

Uncorrelated noise is called

A

White noise

177
Q

An object size-independent measure of the signal level in the presence of noise

A

Contrast to noise ratio

178
Q

One of the most meaningful metrics that describes the conspicuity of an object— how well it be seen by the typical observer

A

Signal-to-noise ratio

179
Q

Describes the overall frequency-dependent SNR performance of the system

A

Detective quantum efficiency