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Ther 205: Modalities > Midterm: Lecture 3 > Flashcards

Midterm: Lecture 3 Flashcards

1
Q

Positive pressure wave

A

Compression

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2
Q

Negative pressure wave

A

Rarefraction

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3
Q

Waves have 2 modes

A

longitudinal- same direction as compression/ decompression and shear- happen in solids (hits bone and travels along periosteum

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4
Q

Acoustic impedance

A

relative resistance of the medium to the wave energy.

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5
Q

What is the relationship between absorption and penetration

A

inverse relationship. The more it absorbs the less it penetrates

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6
Q

If the wave is held (keep head stationary) a stationary wave could form

A

standing wave

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7
Q

Crystal in head of ultrasound head:

A

contracts which causes molecules in tissue to compress and decompress

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8
Q

How to ensure you dont get a shearing wave

A

Move head at all times
Change settings so don’t hit done
Keep ultrasound flat

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9
Q

Frequency

A

number of cycles per second

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10
Q

Therapeutic US is in the range

A

1-3 MHz

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11
Q

Intensity

A

Magnitude of force in a sound wave, expressed in Watts/ cm2

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12
Q

Cavitation

A

effect of small gas bubbles growing and then contracting in harmony with the sound wave.

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13
Q

Non-thermal effects

A

vibration, effects cell membrane, stable cavitation.

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14
Q

acoustic streaming

A

movement of these gas bubbles

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15
Q

Cell Membrane Effects

A

increased permeability which allows various ions and chemicals to diffuse into cell

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16
Q

Absorptive levels

A

blood and air low

bone high

17
Q

How large can area be treated by US

A

no more than 2x bigger than the head

18
Q

Why is gel used?

A

to decrease resistance or prevent standing wave

19
Q

Contraindications

A 
Abnormal growths
Tissue receiving radiation therapy
Low back or abdomen of a pregnant female
Epiphyseal plates of children
Pacemaker
20
Q

Standard heating times

A

8-10 mins

Ther 205: Modalities (13 decks)

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