SPI 2 Flashcards
1
Q
Absorption
A
Process where sound energy is dissipated in a medium
Heat
2
Q
Acoustic
A
Having to do with sound
3
Q
Acoustic impedance
A
Resistance to sound as it propagates through a medium
4
Q
Acoustic variables
A
Effects on the sound beam caused by the medium
Pressure, density, distance
5
Q
Amplitude
A
Strength of the compression wave; maximum variation of an acoustic variable
6
Q
Attenuation
A
Weakening of sound as it propagates through a medium
7
Q
Attenuation coefficient
A
Attenuation occurring with each centimeter that sound travels
8
Q
Bandwidth
A
Range of frequencies found in pulse Ultrasound
9
Q
Compression
A
Region of high pressure or density in a compression wave
10
Q
Continuous wave
A
A nonpulsed wave in which cycles repeat indefinitely
11
Q
Cycle
A
One complete variation in pressure or other acoustic variable
12
Q
Decibel
A
A unit used to compare the ratio of intensities or amplitudes of two sound waves or two points along the wave
13
Q
Density
A
Concentration of mass weight or matter per unit volume
14
Q
Duty factor
A
Fraction of time that pulse Ultrasound is on
15
Q
Frequency
A
Number of cycles in a wave occurring in one second
16
Q
Half value layer
A
Thickness of tissue required to reduce the intensity of the sound beam by one-half
Aka- depth of penetration
17
Q
Harmonic frequency
A
Echoes twice the frequency transmitted into the body that reflect back to the transducer, which improves image quality
18
Q
Impedance
A
Determines how much of an incident sound wave is reflected back from the first medium and how much is transmitted into the second medium
19
Q
Incident angle
A
Direction and of incident beam with respect to the media boundary
20
Q
Intensity
A
Rate at which energy transmits over a specific area
21
Q
Oblique incidence
A
Incident Ultrasound traveling at an oblique angle to the media boundary
22
Q
Period
A
Time to complete one cycle
23
Q
Pressure
A
Concentration of force
24
Q
Propagation speed
A
Speed at which a wave moves through a medium
25
Pulse
Collection of a number of cycles that travel together
26
Pulse duration
Portion of time from the beginning to the end of a pulse
Sonography 2-3 cycles
Doppler 5-30 cycles
27
Pulse repetition frequency
Number of pulses per second
28
Pulse repetition period
Time between the beginning of one cycle and the beginning of the next cycle
29
Q factor
For short pulses the Q factor is equal to the number of cycles in a pulse; the lower the Q factor the better the image quality
30
Rarefraction
Regions of low pressure or density in a compression wave
31
Rayleigh's scatter
Occurs when the reflector is much smaller than the wavelength of the sound beam
32
Reflection
Redirection (return) of a portion of the sound beam back to the transducer
33
Refraction
Change in direction of the sound wave after passing from one minute to another
34
Scattering
Redirection of sound in several directions on encountering a rough surface (non speculate reflection)
35
Spatial pulse length
Distance over which a pulse occurs
36
Speckle
Multiple echoes received at the same time generating interference in the sound wave, resulting in a grainy appearance of the US
37
Specular reflections
They compromise the boundaries of organs and reflect sound in only one direction. Angle dependent
38
Stiffness
Resistance of a material to compression
39
Temporal
Relating to time
40
Wavelength
Distance of one cycle
41
Sound categories
Infra - below 20Hz (below human hearing)
Audible- above 20Hz and below 20,000Hz (human hearing)
Ultrasound- over 20,000 Hz (above human hearing)
42
Sound waves carry?
Energy
43
Sound waves have areas of?
Compression (high pressure) and rarefraction (low pressure)
44
Frequency is proportional to?
Image quality and attenuation
45
Frequency is inversely proportional to
Wavelength, period and depth
46
Period is proportional to?
Wavelength
47
Period is inversely related to
Frequency
48
Propagation speed is proportional to
Stiffness in a medium
49
Propagation speed is inversely related to?
Density of a medium
50
Dense structures or pathology do what to propagation speed?
Decrease
51
Stiff structures do what to propagation speed?
Increase
| Bone
52
Propagation speed of soft tissue
1.54 mm/ms
53
Wavelength is proportional to?
Period and depth
54
Wavelength is inversely related to?
Frequency
55
Amplitude
Sound strength
56
Amplitude is proportional to
Power
57
Amplitude does what through tissue?
Decreases
58
Intensity is proportional to
Power and amplitude of the wave squared
59
Intensity is inversely related to
Beam area
60
Power
Rate at which energy is transmitted into the body
61
Power is proportional to
Intensity
62
Pulse Ultrasound
A few pulses of Ultrasound followed by a longer pause of no ultrasound
Two components: transmitting and receiving
63
Bandwidth relationships
Inversely related to SPL and Q factor
64
Duty factor relationships
Directly related to PRF and pulse duration
| Inversely related to PRP
65
Pulse duration relationships
Directly related to duty factor and number of cycles in pulse
Inversely related to PRF
66
PRF relationships
Proportional to duty factor
| Inversely related PRP and imaging depth
67
PRP relationships
Proportional to imaging depth
| Inversely related to PRF
68
Spatial pulse length relationships
Directly related to wavelength and number of cycles per pulse
Inversely related to frequency
69
Sound travels through tissues at different speeds depending on?
Density and stiffness of a medium
70
Sound travels faster in media that is denser than air because of
reduced compressibility
71
Normal incidence
Allows reflection of sound beam.
72
Oblique incidence
When incident sound beam strikes another boundary at any angle other than 90 degrees
73
What must take place for reflection to occur?
A difference in acoustic impedance between two structures and striking the boundary at a perpendicular angle
74
Harmonics frequency improves
Spatial and contrast resolution
75
Harmonics frequency decreases
Axial resolution
76
Harmonics frequency sound beams are
Narrower with lower side lobes increasing lateral resolution
77
Increasing depth does what to harmonics frequency?
Increases harmonic signals
78
Tissue harmonics created when?
During transmission
79
Contrast harmonics are created
During receiving
80
What must take place for refraction to occur?
Oblique incidence and a change in velocity or propagation speed between two media
81
Absorption
Conversion of sound to heat
82
Reflection
Redirection of sound beam back to transducer
83
Scattering
Redirection of sound in multiple directions
84
Attenuation relationship
Proportional to frequency and depth
85
Attenuation coefficient relationship
Proportional to frequency and depth
86
Density relationship
Proportional to impedance and propagation speed
87
Half value layer relationship
Inversely related to frequency
88
Impedance relationship
Proportional to density and propagation speed of the medium
89
Divergence
Widening of sound beam in the far field
90
Aperture
Size of transducer element
91
Apodization
Excitation of elements in an array to reduce grading lobes
92
Array
Collection of active elements connected to individual electronic currents in one transducer assembly
93
Axial resolution
Ability to distinguish two structures along a path parallel to the sound beam
94
Channels
Multiple transducer elements with individual wiring and system electronics
95
Constructive interference
Occurs when two waves in phase with each other create a new wave with amplitude greater than the original two waves;in phase
96
Convex array
Curved linear transducer containing multiple piezoelectric elements
97
Curie point
Temp to which a material is raised while in the presence of a strong electrical field, to yield piezoelectric properties.
98
What happens when temperature exceeds Curie point?
Crystal properties will be lost
99
Damping
Material attached to rear of transducer element reduce ringing
100
Destructive interference
Occurs when two waves out of phase with each other create a new wave with amplitude less than the two original waves
101
Diffraction
Deviation in the direction of the sound wave that is not a result of reflection, scattering, or refraction
102
Dynamic aperture
Aperture that increases as the focal length increases; minimizes change in the width of the sound beam
103
Element
Piezoelectric element of the transducer assembly
104
Elevational resolution
Detail resolution located perpendicular to the scan plane; it is equal to the section thickness and is the source of slice thickness artifact
105
Far zone
Region of the sound beam in which the diameter increases as the distance from the transducer increases
106
Focal length
Distance from a focused transducer to the center of the focal zone; distance from a focused transducer to the spatial peak intensity
107
Focal point
Concentration of the sound beam into a smaller area
108
Focal zone
Area at region of focus
109
Fraunhofer
Far zone
110
Fresnel
Near zone
111
Grating lobes
Additional weak beams emitted from a multi element transducer that propagate in directions different from the primary beam
112
Huygens principle
All points on a wave front or at a source are point sources for the production of spherical secondary wavelets
113
Interference
Occurs when two waves interact or overlap resulting in the creation of a new wave
114
Lateral resolution
Ability to distinguish two structures lying perpendicular to sound path
115
Matching layer
Material attached to front face of the transducer element to reduce reflections at the transducer surface
116
Near zone
Region of beam between the transducer and focal point which decreases in size as it approaches the focus
117
Operating frequency
Natural frequency of the transducer
118
Operation frequency is determined by
Propagation speed and thickness of element in pulse Ultrasound and by the electrical frequency in continuous wave
119
Phased
Multiple focal zones, beam steering and beam focusing
Applies voltage pulse to all elements in the assembly as a group, but with minor time differences.
120
Sequenced array
Operated by applying voltage pulses to a group of elements in succession
121
Side lobes
Additional weak beams traveling from a single element transducer in directions different from the beam
122
Subdicing
Dividing each element into small pieces to reduce grading lobes
