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24 Cards in this Set
- Front
- Back
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Sound Propagation
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Longitudinal wave
Transverse Wave Standing Wave |
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Attenuation
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How mucha energy is lost as it goes into the body tissue
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Acoustic Impedance
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The resistance of a medium to the flow of energy
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What is the main propagation of ultrasound in soft tissues
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the longitudinal or compressional wave
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What is the order of the waves as they enter the body
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Longitudinal
When the waves hit the bones and bounce back Standing wave |
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Shear wave
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occurs when the pressure wave reaches the bone
-does not produce a significant heating in the tissue |
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True or false, ultrasound transducers are exchangeable between units
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False. Pg 128
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What happens if the sound head isnt moved consistently
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energy summates and results in a standing wave
Will heat the bone! |
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wave travel depends on
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the closeness of the molecules
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what is the relationship between the density of molecules and the impedences
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The more dense the molecules, the greater the impedance and Reflection
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Which elements in the body have the highest and lowest impedance values and acoustic absorption
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Highest= bone
Lowest= fluid |
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how does the dispersement of tissue molecules affect absorption
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the more dispersed the molecules, the less the amt of absorption
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Attentuation
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a decrease in the intensity of the energy which is due to either absorption of the energy by the tissue or due to a scattering of the sound wave from reflection or refraction
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Factors to be considered with ultrasound
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Area to be treated-volume/depth/acuity
Frequency Duty Cycle Duration Intensity Goals of Treatment |
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The goals of treatment refers to
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Stage of healing
Pain Mechanism of injury |
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What is the most significant factor in determining tissue response
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Intensity
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Pulsed ultrasound is AKA
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duty cycle
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Most commonly used duty cycle
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20% (on 20 sec, off 80)
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1 MHz penetrates to a depth of
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5-7 cm
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3 MHz penetrates to a depth of
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1-2 cm
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Non thermal
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Used for Healing
use low intensity and pulsed mode delivery Facilitates healing of tissue |
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Thermal effects of US
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increased metabolic rate
Decreased pain and muscle spasm Alteration of N. Conduction velocity Increased circulation Increased soft tissue extensibility |
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what is the window of opportunity for stretching after applying US
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5-10 min
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Non Thermal/ Mechanical Effects of US
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Cavitation
Acoustic Streaming Micro Massage |
