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Definition
| In DMS, the ultrasound system and the transducer, which establishes the quantity or level of some parameters |
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Definition
| The material through which sound travels; tissue |
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Term
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Definition
The time required for a wave to complete a single cycle; the time between the start of one cycle to the start of the next cycle
Determined by the sound source only
Cannot be adjusted by the sonographer
Typical values: 0.06-0.5 microseconds (µs) |
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Term
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Definition
The number of events that occur in a specific duration of time, generally, one second
Unit = 1 cycle/second = 1 hertz (Hz)
Determined by sound source
Cannot be changed by sonographer
Typical values: 2-15 MHz
Determines whether a sound is ultrasound (<20 kHz), audible (20 Hz - 20 kHz), or infrasound (<20 Hz) |
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| Parameters/Properties with Inverse (Reciprocal) Relationships |
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Definition
Period and Frequency
Wavelength and Frequency
Density and Speed |
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Definition
Parameters that describe how big/strong a wave is
Amplitude
Power
Intensity |
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Definition
The height of a wave; the difference between the max or min value and average/undisturbed value of an acoustic variable; γ
Determined by sound source
Can be altered by the sonographer by adjusting depth as amplitude decreases as sound propagates through the body
Units are same as acoustic variables: pascals, cm3, particle motion/distance
Typical values: 1-3 million/mega pascals (MPa) |
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Definition
| The difference between max and min values of an acoustic variable; twice the value of the amplitude |
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Definition
The rate of energy transfer
Determined by the sound source
Can by changed by the sonographer by adjusting the depth; decreases as sound propagates through the body
Units = watts (W)
Typical values: 0.004-0.09 watts (4-90 mW) |
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Term
| Parameters/Properties with Direct Relationships |
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Definition
Wavelength and Period
Power and Amplitude: power ∝ amplitude2
Power and Intensity: power ∝ intensity
Intensity and Amplitude: intensity ∝ amplitude2
Stiffness and Propagation Speed |
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Term
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Definition
The concentration of energy in a sound beam; power ÷ beam area (watts/cm2)
Determined by sound source
Can be changed by sonographer via changes to power
Typical values: 0.01-300 W/cm2
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Term
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Definition
The length/distance of a single complete cycle
λ = propagation speed÷ frequency = mm/μs ÷ MHz
Determined by sound source AND medium
Cannot by changed by the sonographer
Typical values: 0.1-0.8 mm (in soft tissue) |
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Term
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Definition
The rate that sound travels through a medium; distance that sound travels in 1 second
C = frequency*λ
Determined by medium
Units = mm/μs
Fastest in solids, slower in liquids, slowest in gases
Related to *stiffness* and density
Lungs < fat < water < soft tissue< bone
Avg for soft tissue = 1.54 mm/μs |
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Term
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Definition
A medium's ability to be moved
AKA bulk modulus |
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Definition
| How closely packed the molecules in a medium are; related to the medium's weight |
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| Propagation Speed by Medium (m/s) |
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Definition
Air = 300
Lungs = 500
Fat = 1450
Water = 1480
Soft Tissue (avg) = 1540
Liver = 1560
Blood = 1560
Muscle = 1600
Tendon = 1700
Metals = 2000-7000
Bone = 3500 |
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