definitions Flashcards
(118 cards)
1
Q
a type of wave that carries energy , not matter from place to place
A
Sound
2
Q
the effects of the medium upon the sound wave
A
acoustic propagation properties
3
Q
the effects of the sound wave upon the biologic tissues
A
biological effects
4
Q
acoustic variables
A
Pressure, density, distance
5
Q
concentration of force within an area, Force/area
Units= Pascals (Pa)
A
Pressure
6
Q
concentration of mass within a volume
Units= Kg/cm^3
A
Density
7
Q
measure of particles in motion
Units=cm, feet, miles
A
Distance
8
Q
particles move in a perpendicular direction (right angle) to the direction of the sound wave
A
Transverse waves
9
Q
particles move in the same direction as the wave
A
Longitudinal wave
10
Q
regions of higher density and pressure
A
compressions
11
Q
regions of lower density and pressure
A
rarefractions
12
Q
inform us of which waves are sound waves
A
acoustic variables
13
Q
describe the features of a particular sound wave
A
acoustic parameters
14
Q
the time required to complete a single cycle
can also be described as the time from the start of a cycle to the start of the next cycle
A
period
15
Q
number of certain events that occur in a particular time duration
A
Frequency
16
Q
waves with frequencies exceeding 20,000Hz (20KHz)
This frequency is so high that the sound is not audible
A
Ultrasound
17
Q
infrasound
A
sound with frequencies less than 20Hz
18
Q
audible sound
A
heard by man, frequencies between 20Hz and 20,000Hz
19
Q
the difference between the average value and the maximum value of an acoustic variable. The variation of an acoustic variable
A
amplitude
20
Q
the concentration of energy in a sound beam
the beams power divided by the beam’s cross-sectional area
A
Intensity
21
Q
the rate that work is performed, or the rate of energy transfer
A
power
22
Q
the length or distance of a single cycle
A
wavelength
23
Q
the rate that sound travels through a medium.
Also called velocity and speed
A
Propagation speed
24
Q
opposites of stiffness
A
compressibility and elasticity
25
same as stiffness
Bulk modulus
26
a collection of cycles that travel together
a pulse
27
the time from the start of a pulse to the end of that pulse
the actual time that the pulse is on
Pulse duration
28
the length or distance that an entire pulse occupies in space
The distance from the start to the end of one pulse
Spatial pulse length
29
the time from the start of one pulse to the start of the next pulse
It includes one pulse duration and one "listening time"
Pulse repetition period
30
the number of pulses created by the system in one second
Pulse repetition frequency
31
the percentage or fraction of time that the system transmits sound
Duty factor
32
the concentration of the power in a beam
intensity
33
a logarithmic scale
a relative scale
a comparison, therefore, two intensities are needed to calculate decibels
Decibels
34
the decrease in intensity, power and amplitude of a sound wave as it travels
This is unrelated to speed
attenuation
35
the amount of attenuation per centimeter
*a way to report attenuation without dealing with distance
attenuation coefficient
36
transmission with a bend
a change in direction as sound transmits from one medium to another
refraction
37
any device that converts one form of energy into another
transducer
38
when PZT is heated above this temperature (approximately 360C degrees or 680F degrees), it loses its piezoelectric properties, ( the PZT is depolarized)
Curie temperature / Currie point
39
the complete destruction of all living microorganisms by means of exposure to heat, chemical
sterilization
40
the application of a chemical agent to reduce or eliminate infectious organisms on an object, such as a transducer
disinfection
41
the piezoelectric crystal, also called the ceramic, PZT, or crystal
1/2 wavelength thick
Active element
42
the range of frequencies
bandwidth
43
a unitless number representing the extent of damping
Quality factor
44
the location where the beam reaches its minimum diameter
Focus or focal point
45
the distance from the transducer face to the focus. also called focal length or near zone length
focal depth
46
the region or zone in between the transducer and the focus
*sound beams converge here
Near zone (Fresnel zone)
47
the region or zone deeper than the focus, beyond the near field
*sound beams diverge here
Far zone (Fraunhofer zone)
48
the region surrounding the focus where the beam is "sort of narrow" and the picture is relatively good
Focal zone
49
V-shaped wave, also called a Huygen's wavelet
Diffraction
50
explains the hourglass shape of an imaging transducer's sound beam
Huygen's principle
51
the ability to image accurately
Resolution
52
the ability to distinguish two structures that are close to each other front to back, parallel to, or along the beams main axis
axial resolution
53
the minimum distance that two structures are separated by side-to-side or perpendicular to the sound beam that produces two distinct echoes
Lateral resolution
54
a collection of active elements in a single transducer
array
55
a single slab of PZT cut into separate pieces called elements
element
56
combination of electronic circuitry, the wire and the element
channel
57
a collection or elements in a line
1. linear switched (sequential) array
2. linear phased array
Linear array
58
a group of ringed elements (bull's eye) with a common center
annular array
59
elements arranged in an arc
1. convex switched (sequential) array
2. convex phased array
convex, curved, or curvilinear array
60
adjustable, or multifocus; achieved electronically
Phased arrays
61
creates electronic patterns. Delays are approximately 10 nanoseconds
beam former
62
phase delays during reception can be applied to the electrical signals from the transducer to the US system.
This provides focusing at many depths during reception
Dynamic receive focusing
63
the production of a motion picture
Real time imaging
64
the ability to accurately locate moving structures at any particular instant in time
Temporal resolution
65
communicates with all of the individual components of the ultrasound system
organizes and times their functions, so as to operate as a single integrated systems
Master synchronizer
66
converts electrical into acoustic energy during transmission and acoustic into electrical during reception
transducer
67
Controls the electrical signals sent to the active elements for sound pulse generation
determines the pulse repetition period, PRF, and pulse amplitude
creates the firing pattern for phased array systems
(called the beam former)
Pulser
68
the electronics associated with processing the electronic signal production by the transducer during reception and producing a picture on a display device
Reciever
69
the device associated with the presentation of processed data for interpretation
>>monitor, audio speakers, a paper record
Display
70
any number of devices and "media" that are used to permanently archive the US data
>>computer memory, hard drive, (NAS, network attached storage)
Storage
71
increases the strength o f all electronic signals in the receiver prior to further processing
Amplification
72
used to create image of uniform brigthness from top to bottom
compensation
73
reducing the total number of signals, from the smallest to the largest
compression
74
changes the signal's form to one more suitable for display
demodulation
75
Displays low level echoes only when they are clinically meaningful. Very low level echoes are not always important.; eliminates Low-level noise in our images
Reject
76
also called "micro-bubbles"
have different acoustic fingerprint than blood or tissue,
create strong reflections
contrast agents
77
affects brightness by adjusting the strength of the sound waves sent to the body from the transducer. affects patient exposure
output power
78
affects the brightness by changing the amplification of the electronic signals after returning to the receiver
Receiver gain
79
creates ultrasound scans from sound reflections at twice the transmitted frequency
harmonic imaging
80
the frequency of the transmitted sound wave
fundamental frequency
81
twice the transmitted frequency also called the second harmonic
harmonic frequency
82
changes the data format from penetrations (spokes) to horizontal lines of a display . Made gray scale displays possible
Scan converters
83
a microprocessor digitizes images. This converts the image into numbers which are stored in memory. The numbers can be processed and then retranslated for display as an image
Digital scan converter
84
the smallest element of a digital picture
pixel
85
the more pixel per inch, the more detail in the image, spatial or detail resolution
Pixel density
86
the smallest amount of digital storage
Bit
87
a group of bits,
| a series of zeroes and ones
binary number
88
a group of 8 bits, 2__________ equal a word
byte
89
manipulating the data before storage in the scan converter, it carrot be reversed or "undone"
preprocessing
90
related to the ability of humans to see the gray scale differences in anatomic structures. Lowers the high level echoes and boosts the low level echoes.
log compression
91
manipulating the data after it has been stored in the scan converter memory but prior to display . increases versatility of the display process.
can be undone
Postprocessing
92
images can be improved by filling in gaps between lines
| is pre-processing
Fill-in interpolation
93
Scan lines are steered by the transducer in different directions or views, so structures are interrogated by multiple pulses from several different angles
Spatial compounding
94
a form of electronic receive focusing
dynamic aperture
95
creates an element of realism to a 3-D or 4-D image
rendering
96
the ratio of the largest to the smallest signal strength that each component processes, the number of choices indicated the number of gray shades on an image
Dynamic range
97
Picture Archiving and Communications System
PACS
98
Digital Imaging and Communications in Medicine
Provides standards or guidelines for imaging networks
DICOM
99
Network storage devices
high storage capacity disc drives, economical, used in PACS systems
NAS (Network Attached Storage)
100
the movement of a fluid from one location to another
flow
101
Fluid moving at a constant speed or velocity
steady flow
102
blood moves with a variable velocity
pulsatile and phasic flows
103
flow streamlines are layered, aligned and parallel
plug or parabolic patterns
laminar flow
104
chaotic flow in many directions and speeds
turbulent flow
105
a unitless number indicating whether flow is laminar or turbulent
Reynold's number
106
Blood flows when the total fluid energy at one location differs from the total fluid energy at another location
energy gradient
107
Motion energy, associated with an objects speed and mass
Kinetic energy
108
a form of potential or stored energy that has the ability to perform work
Pressure energy
109
the conversion of other forms of energy into heat
friction
110
describes the thickness of a fluid
viscosity
111
relates to the tendency of a fluid to resist changes in its velocity
inertia
112
a narrowing or irregularity in a lumen
stenosis
113
equals the weight of blood pressing on the vessel from heart level to the point of measurement
hydrostatic pressure
114
a change or variation in the frequency of sound as a result of motion between the sound source and the receiver (a moving interface)
Doppler shift
or
Doppler frequency
115
extracts the Doppler frequency from the transducer frequency and is preformed by a demodulator.
Demodulation
116
magnitude only
speed
117
magnitude and direction
velocity
118
the Doppler frequency at which aliasing occurs, equal to half the PRF
Nyquist frequency
