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Modalities > Lecture 4 > Flashcards

Lecture 4 Flashcards

1
Q

What is Therapeutic Ultrasound?

A

it is a deep-penetrating agent that produces changes in tissue through thermal & non-thermal (mechanical) mechanisms

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2
Q

What type of heat transfer is U/S?

A

conversion transfer

  • converting one form of energy into another
  • sound wave will oscillate tissue and produce heat
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3
Q

What is the Piezoelectric Effect?

A
  • Electric charge travelling through a piezoelectric crystal

- high frequency alternating current is introduced to the crystal causing it to expand & contract producing a sound wave

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4
Q

What does acoustic energy rely on for transmission

A

-acoustical energy relies on molecular collision for transmission

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5
Q

How does a P-wave (primary) work?

A

compressional wave - molecules collide & bend forward & elastically rebound - travels through the material in the direction of the release

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6
Q

How does a S-wave (secondary) work?

A

sliding & rebounding against rigid material - in liquid a shear wave doesn’t transmit but in bone it does

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7
Q

How do Longitudinal Waves work?

A
  • displacement of particles occurs parallel to the direction of the sound
  • combination of rarefaction & compression
  • capable of passing through liquids & solids (doesn’t pass through gas well)
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8
Q

How do Transverse (shear) Waves work?

A
  • Perpendicular to the direction of the sound waves
  • common in solids
  • occur when ultrasound hits a bone
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9
Q

What are Standing Waves?

A
  • occurs when U/S travelling through tissues of various impedance
  • when reflected wave meets incoming incident wave
  • increases intensity of the energy creating areas of high & low pressure
  • can be avoided by keeping the sound head moving
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10
Q

How does the Frequency of U/S work?

A
  • measured in cycles per second (Hz)
  • size & shape of crystal determines the frequency
  • divergence vs. collimating
  • the lower the frequency (1mHz) the greater the divergence (3mHz)
  • frequency determines depth of penetration
  • frequency also determines the rate of absorption
  • w/a higher frequency you will get a greater rate of absorption
  • superficial
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11
Q

What are the types of U/S?

A

Continuous & Pulsed

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12
Q

What is Continuous U/S?

A
  • continuous waves which come out a constant speed & within an equal distance
  • generates thermal effects as well as mechanical effects
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13
Q

What Pulsed U/S?

A

Bursts of waves (interrupted at various rates)

-Generates non-thermal effects only

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14
Q

What does the Duty Cycle of U/S consist of?

A

it is the duration of how long the pulse is on

i. e.
- pulsed ratio
- on for 1 off for 5

10% = 1/10 (on for 1, off for 9)

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15
Q

What is Propagation?

A
  • velocity at which the vibration is propagated through the conduction medium is directly related to the density
  • denser materials will have a higher velocity of transmission
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16
Q

EXAM Q: Define Half-Value, Half Layer Rate

A

depth at which 50% of the ultrasonic energy has been absorbed by the tissue

17
Q

EXAM Q: What is Half Value Distance?

A
  • 3MHz sound head = effects occur at 1.5cm (.8 to 3cm according to starkey)
  • 1MHz sound head = effects occur 5cm
18
Q

What is Effective Radiating Area (ERA)?

A
  • the area of the U/S head that produces mechanical waves, normally measured in cm2
  • measured 5mm from the faces of the sound head, the ERA represents all areas producing more than 5% of the max. power output of the transducer
  • always lesser area that the actual size of the transducers face
19
Q

What materials can you use as Coupling Agents?

A
  • Gel
  • Petroleum based creams
  • water based lotions
  • immersion in water -1/4 inch to 1/2 inch from treatment area
  • temperature of coupling agent
  • phonophoresis
20
Q

How could you use cold for adhesive capsulitis (frozen shoulder)?

A

Want to reduce pain so you can take them through full ROM

21
Q

What is acoustic spectrum

A

Acoustic energy requires a medium for transmission of energy

Transmitted by mechanical waves that deform the medium

22
Q

Any hard substance when compressed that lets off a current is _____ in nature

A

piezoelectric

23
Q

What is acoustic energy?

A

Mechanical wave in which energy is transmitted by the vibrations of the molecules of the biological medium through which the wave is traveling

24
Q

ultrasound cannot pass through the skin dry - to get passed the skins barrier ultrasound requires a ____

A

medium

25
Q

What is more specific in whats its targeting 3mhz or 1mhz

A

3mhz

26
Q

What penetrates deeper 1mhz or 3mhz

A

1mhz

27
Q

general rule of thumb is always use ____ frequency possible to accomplish depth of penetration

A

general rule of thumb is always use highest frequency possible to accomplish depth of penetration

Modalities (10 decks)

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