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Modalities > Therapeutic US > Flashcards

Therapeutic US Flashcards

1
Q

What is principle #1 of US wave transmission?

A
  • in wave motion, the particles stay close to the same spot, while the energy of the wave travels through the medium.
  • each particle vibrates back and forth in close to the same spot, when affected by the wave.
  • Ex: each metal ball says in the same position in the line of balls but swings back and forth when it is influenced by the wave
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2
Q

What is clinical correlation #1 of US wave transmission?

A
  • The particle of affected tissue vibrate back and forth and these vibrations (thermal effect of US) produce heat.
  • produces cavitation (non thermal effect of US)
  • gas bubbles shrink and expand
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3
Q

What it cavitation?

A

The tiny micron sized air bubbles formed by the vibration of the sound wave

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4
Q

What is stable cavitation?

A
  • occurs with the ebb and flow along with small changes in the bubble radius
  • contributes to increased cell permeability
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5
Q

What is unstable cavitation?

A
  • can occur if the air bubbles become too large and pop
  • similar to “tiny hand grenades going off in the body’s tissue”
  • causes tissue damage
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6
Q

How do achieve beneficial therapeutic effects and not damaging one?

A
  • dependent on how the treatment parameters are set

- treatment parameters affect the size and stability of the tiny air bubbles

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7
Q

How does intensity affect cavitation?

A
  • increase in intensity = particles swing further and further apart with each swing causing tiny bubbles to get bigger and bigger and finally pop (tissue damage)
  • not enough intensity does not cause a therapeutic effect
  • in human tissue intensity affects how far the tissue particles vibrate back and forth.
  • as particles vibrate there is a spot when the particles are close together (compression) and when they are far apart (rarefaction).
  • ex: how far the metal ball swings as it moves back and forth
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8
Q

How does frequency affect cavitation?

A
  • in human tissue frequency is the # of waves passing through a particular spot in a given second.
  • low frequency = each wave more time to displace the tissue particles before the next wave–> gives bubbles longer time to get big enough to pop
  • if constant intensity- low frequency = unstable cavitation; high frequency = stable cavitation
  • high frequency required for fragile tissues
  • ex. frequency is # of waves that pass down the row of metal balls in a given time.
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9
Q

What is principle #2 of US wave transmission?

A
  • as any wave travels through a medium, some of the wave’s energy is used up or absorbed by the movement of the particles in the medium.
  • more energy absorbed by the medium = less distance the wave can travel before running out of energy
  • Ex: metal ball too heavy the wave won’t travel down the whole row of balls
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10
Q

What is clinical correlation #2 of US wave transmission?

A
  • with US, factors that increase the rate of absorption will decrease the depth that the US will penetrate into the tissue
  • quick absorption = decreased penetration
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11
Q

How does frequency affect US depth of penetration?

A
  • high frequency of US = shallow depth (3 MHz- 1-3cm)
  • low freqency of US = deeper penetration (1 MHz- 3-5cm)
  • high frequency sound waves vibrate faster, expend energy sooner and over a shorter distance than low frequency
  • ex: fast the metal balls swing back and forth the more resistance is created and the more energy gets absorbed
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12
Q

How does tissue type affect US depth of penetration?

A
  • tissues with particles that are heavier and harder to compress absorb more energy
  • tissues with particles that are lighter and compress more easily absorb less energy
  • Bone, ligaments, joint capsules, and tendons absorb more energy and greater heating effects and shallower penetration (use 3 MHz)
  • Blood and muscles will have less heating effect but deeper penetration (use 1 MHz)
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13
Q

What is principle #3 of US wave transmission?

A

-when a wave travels from one medium to another medium with a much different density, some of the wave energy may be reflected back into the original medium or the path of the wave may be bent or refracted

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14
Q

What is the clinical correlation #3 of US wave transmission?

A

-with US waves, traveling from air to human tissue or from muscles to bones can be problematic

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15
Q

What is important about the air tissue interface?

A
  • air to tissue- need coupling medium (no bubbles) to transmit US waves due to the difference in densities; reflection might be sufficient to damage the sound head.
  • Always keep sound head in contact with the coupling medium and the body when sound waves being transmitted.
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16
Q

What is important about the muscle (or other tissue) interface?

A

-muscle (or other tissue) interface- will heat up more quickly due to significant reflection (25%) so lower intensity required and important to keep sound head moving to avoid unstable caviation

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17
Q

What is important about the skin/muscle/blood interface?

A

-reflection and refraction at the skin/muscle/blood interface are insignificant due to similar densities and similar acoustic properties

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18
Q

What is principle #4 of US wave transmission?

A

-the wave energy of US is propagated through the tissue in a roughly cylindrical beam, with some divergence as the beam progresses through the tissue

19
Q

What is clinical correlation #4 of US wave transmission?

A
  • lower frequencies result in a more divergent beam than higher frequencies.
  • smaller sound head result in a more divergent beam than larger sound heads
  • there is an uneven distribution of the US energy in the bean with the highest level of US energy concentration in the middle 1/3 of the beam.
20
Q

What does BNR stand for and what does it mean?

A
  • Beam nonuniformity ratio
  • Measures the ratio between the highest peaks of energy concentration and the average energy concentration in the US beam.
  • ratio 15:1 means hottest spot in the beam are receiving 15x more US energy; this could result in tissue damage
  • BNR of 6:1 or lower is considered acceptable.
  • lower BNR = more expensive US machine
21
Q

What are the indications for US?

A
  1. well defined localized tissue problem
  2. Tissue repair (low intensity pulsed)
  3. Heat and stretch (higher intensity continuous)
  4. Efficient use of time
  5. accessibility of target tissue
  6. is it practical?
  7. if applying medications, iontophoresis may be preferable
22
Q

What are the contras for US?

A
  1. not over a pacemaker
  2. not under the ribs, directly aimed at the heart
  3. Not over carotid sinus (might change heart rate or affect baroreceptors)
  4. Not over cervical ganglia (might change HR or affect baroreceptors)
  5. Not over spinal cord after a lamenectomy
  6. Not over the eyse
  7. Not over gonad
  8. Not over low back or abdomen during pregnancy
  9. Thrombus, DVT
  10. All the general contras for heat (except for non-thermal application)
23
Q

What are the precaution for US?

A
  1. Keep sound head moving and in contact with tissues and coupling medium whenever intensity is greater than zero.
  2. Patient complaints of pain are an indication that the periosteum may be overheating. Decrease intensity, stop treatment, or move the transducer more quickly.
  3. If treating tissues around metal or plastic implants, use very low intensity only. (metal reflects, plastic absorbs)
24
Q

What is the coupling agent for indirect US?

A

water

25
Q

How do you perform underwater US?

A
  • use continuous US
  • will not heat tissues for 0-1.5” deep because heat absorption by water
  • will heat tissues 1.5”-3” deep
  • Pt will not report skin warmth under water
  • keep sound head moving 1.5” away from body area and increase intensity by 50%
26
Q

What should the size of treatment area be when using US?

A

-Should not be greater than 2-3 times the ERA (effective radiating area) which is slightly smaller than the sound head.

27
Q

How long does it take to reach therapeutic heating with US?

A

to reach 40 C it takes 5-15 minutes if treatment is focused in area 2X sound head

28
Q

What does it take to increase tissue close to bone 4-6 C?

A

1 MHz and 1 w/cm^2

29
Q

Where are thermal effects of US most effective?

A
  1. tissues 3” or less deep
  2. tissues near the bone
  3. tissues with high protein content such as ligaments, tendons, joint capsules, etc.
    Thermal effects are not as effective for larger deeper muscles such as quads, glutes, gastrocs–> diathermy may be more effective
30
Q

What does steroid use do to US effectiveness?

A

steroids may lessen effectiveness of US

31
Q

What are the advantages of US over other heating modalities?

A
  1. greater depth (except for diathermy)
  2. better control of dosage
  3. constant dose throughout treatment
  4. can be morespecific about area treated
32
Q

What are the disadvantages of US over other heating modalities?

A
  1. there are additional contraindications

2. pt must be attended throughout treatment

33
Q

How is intensity of US documented?

A
  • w/cm^2
  • it is the average power distributed over the ERA of the transducer
  • make sure display shows w/cm^2 and not just W
34
Q

Describe the US transducer.

A
  • has a crystal that contracts and expands due to the applied alternating current
  • crystal is housed in the tansducer = the sound head
  • be careful to not drop the sound head and must have contact with coupling medium when US turned on
35
Q

Is pt position with US important?

A

Yes!

36
Q

What is the technique for US?

A
  • slow overlapping circles or linear to distribute the max intensity evenly, parallel to tissue surface
  • adjust to contours
  • “point towards the target”
37
Q

What is pulsed US?

A
  • discontinuous flow of sound wave energy
  • the percent of on time of actual US output is duty factor
  • duty factor = pulse duration divided by the pulse period ex: output on for 1 msec and off for 1 msec, pulse duration is 1 and pulse period is 2 (1+1)–>results in a 50% duty cycle
38
Q

What is continuous US?

A
  • uninterrupted flow of sound wave energy.

- has a duty cycle of 100%

39
Q

Why choose pulsed or continuous US?

A

-will determine the type of thermal and non-thermal effects on the tissues

40
Q

What are the thermal physiological effects of US?

A

Comes from CONTINUOUS US

  1. decrease pain (can get with pulsed too)
  2. increase metabolic rate
  3. increase blood flow and increase immune response
  4. increase extensibility and decrease viscosity of soft tissue
41
Q

What are the non-thermal physiological effects of US?

A

comes from continuous OR pulsed

  1. increase cell membrane or capillary wall permeability (allows ions such as calcium to diffuse into cells; enhances inflammatory response to help with tissue repair)
  2. increased capillary density and increase blood flow
  3. increase protein synthesis
  4. increase wound contraction
  5. increase cellular activity
  6. decrease pain
42
Q

What is an example, low intensity pulsed (non-thermal) treatment protocol?

A

Why? tissue healing, promote cellular activity, acute condition
Intensity: 1.0 (or lower) - 2.5 w/cm2, 20% duty cycle
Recognize that intensities at the higher part of the range will provide a small amount of thermal effects
Frequency: depends on target tissue depth
Time: 5 min per 5cm2 treatment area for soft tissue injuries
2 min per ERA for chronic ulcers

43
Q

What is an example of medium to high intensity continuous treatment protocol?

A

Why? chronic conditions that restrict movement
Intenisty: 0.8 - 1.5 w/cm2
Frequency: depends on target tissue depth
Time: duration and size of are both important; 5 minutes per 5 cm2 ex: 10 min for 10 cm2
-may consider up to 15 minutes if necessary for size of area
Follow treatment with stretch

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