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PT Interventions II > Ultrasound & Lasers > Flashcards

Ultrasound & Lasers Flashcards

1
Q

Ultrasound

A
  • Electrical energy is converted into sound energy
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2
Q

What is the sound head?

A
  • Size ranges from 2cm2 to 10 cm2 (5cm2 is most common)

- Sound head contains a crystal

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3
Q

What is ERA?

A
  • Effective radiating area

- Indicates size of transducer that is producing the vibration

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4
Q

What does the sound head crystal do?

A
  • Expands and contracts as electrical energy passes through it to create mechanical sound energy.
  • Expansion/contraction of the crystal results in compression/decompression of the tissue
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5
Q

Beam Non-Uniformity Ratio

A
  • Phenomenon where some parts of the crystal may release more energy then other areas.
  • Causes sound head to have areas of hot spots and cold spots
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6
Q

What is frequency?

A
  • Measured as number of cycles/second; unit is Hz
  • 1 HZ = 1 cycle/second
    Therapeutic ultrasound frequency = 0.75-3 MHz
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7
Q

Is frequency directly or inversely related to the shape of the wave?

A

Directly related

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8
Q

Is the frequency directly or inversely related to the depth of penetration into the tissue?

A
  • Inversely related.

- Means as frequency goes up, tissue depth decreases.

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9
Q

What is propagation?

A
  • How long it takes for energy to move from one place to another
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10
Q

T/F: Ultrasound propagates faster through less dense tissues than dense tissues.

A

False - the denser the tissue the faster the energy propagates.
- Occurs because the molecules are closer together in denser tissues and are therefore transmitted quicker.

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11
Q

Is ultrasound energy absorbed more in less dense or highly dense tissues?

A
  • More energy is absorbed in more dense tissues because the molecules are tightly packed
  • Results in decreased penetration in denser tissues
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12
Q

When frequency is higher what happens to the tissue penetration?

A
  • As frequency increases penetration decreases because high frequency molecules have to vibrate faster to overcome friction.
  • High frequency = short wavelengths = less penetration
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13
Q

When frequency is lower what happens to the tissue penetration?

A
  • Lower frequencies result in larger wavelengths. Larger wavelengths require less energy or vibration to overcome friction. Therefore tissue penetration increases.
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14
Q

What frequency treats superficial tissues?

A
  • 3 MHz
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15
Q

What frequency treats tissues up to 2-5cm deep?

A
  • 1 MHz
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16
Q

What is attenuation?

A
  • Concept where the beam losses energy as it passes through the tissue.
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17
Q

What occurs when ultrasound energy reflects off of bone?

A
  • Causes the energy to be redirected to surrounding tissues like the muscle, ligaments, tendons, joint capsules
  • Results in pain
    Too much of this can results in bone burning/damage
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18
Q

T/F: Ultrasound beams are more likely to be reflected when the surface skin is dry, thick and callused.

A

True

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19
Q

What is intensity?

A
  • How much energy is contained in the ultrasound beam

- Measured in W/cm2

20
Q

Spatial Power Equation

A 
SP = Intensity (Watts)/Sound head ERA (cm2)
SP= W/cm2
21
Q

Describe Spatial Average Temporal Peak Intensity

A
  • the highest amount of intensity delivered within the ERA during one pulse.
22
Q

Pulsed intensity

A
  • Intensity is periodically interrupted (not on all the time)
  • Can be 25%, 50%, 75%, etc.
  • % indicates how much time the intensity is ON
23
Q

Spatial Average Intensity Equation

A

SAI = Spatial Power (W/cm2) x Time (%)

24
Q

Calculate the spatial average intensity if the spatial power is 2 W/cm2 and the time is 50%

A

SAI = 2W/cm2 x 0.50 = 1W/cm2

25
Q

T/F: If the pulsed time is 75% that means the pulse is on 25% of time.

A

False - pulse is on 75% of the time and off 25%

26
Q

What changes does thermal ultrasound cause in the body?

A
  • Reduce muscle spasms/guarding
  • Change perception of pain
  • Increase nerve conduction velocity
  • Increase blood flow
  • Increase enzymatic activity
27
Q

What needs to occur during ultrasound for scar treatment to be effective?

A
  • 4 degree temperature change
28
Q

What physiological changes in the body does non-thermal ultrasound cause?

A
  • Increase cell membrane permeability
  • Increase histamine release (results in increased blood vessel permeability and inflammatory response)
  • Increase macrophage activity
  • Enhance wound contraction (closing)
29
Q

Ultrasound Contraindications

A
  • Not to eyes, genitals, or heart
  • Do not do over low back or abdomen during pregnancy
  • Not over pacemaker
  • Not over tumors or other abnormal growths
  • Not over infection/abscess
  • Not over ischemic (low blood flow) areas
  • Not over areas with reduced sensation
  • Not on someone w/ current DVT or PE
  • Not over growth plates in children
30
Q

Ultrasound Precautions

A
  • Careful over fracture or joint replacement hardware

- Careful if person has infection (concern of transmission to other patients)

31
Q

What should ultrasound be used for?

A
  • Pain relief
  • Muscle relaxation
  • Increase muscle’s ability to stretch
  • Break up scar tissue
  • Increase blood flow (not in acute stages)
  • Possible wound healing
32
Q

Why does ultrasound head have to be in contact with liquid medium at all times once the ultrasound begins?

A
  • Sound head crystal cannot transmit energy waves through the air; energy therefore becomes trapped and increases within the crystal causing it to break
33
Q

How quickly should the sound head be moved on the skin?

A
  • 4cm/sec
34
Q

Ultrasound Application Types

A
  • Traditional w/ gel
  • Immersion - sound head and tissue underwater
  • Bladder - balloon/glove used; gel applied to both sides
  • Phonophoresis - ultrasound enhances delivery of medication that is applied on the skin into the tissue
35
Q

How deep does 1 MHz ultrasound heat penetrate?

A

3-5 cm

Heats deeper tissues

36
Q

How deep does 3 MHz ultrasound heat penetrate?

A

1-2 cm

Heats superficial tissues

37
Q

What is the desired temperature change of the tissue when using ultrasound?

A
  • 2 degrees F

- 4 degrees F for scar tissue

38
Q

Why is it important to have ultrasound applied at a 90 degree angle to the tissue being treated?

A

Increases chance of greatest amount of ABSORPTION and least amount of reflection

39
Q 
How fast should the sound head be moved during an ultrasound session?
A. 2 cm/sec
B. 3 cm/sec
C. 4 cm/sec
D. > 4 cm/sec
A

C. 4cm/sec

40
Q

Should pulsed or continuous ultrasound be used on acute stage injuries?

A
  • Pulsed only
41
Q

Should 1 MHz or 3 MHz ultrasound be used to treat patellar tendonitis and why?

A
  • 3 MHz because the patellar tendon is a more superficial tissue
42
Q

Is ultrasound created through the piezoelectric or reverse piezoelectric effect?

A
  • Reverse piezoelectric effect

- States electrical energy is converted into mechanical energy (sound in the case of ultrasound).

43
Q

Which BNR ratio for ultrasound would be the least likely to create “hot spots”?
A. 2:1
B. 4:1
C. 6:1

A

A. 2:1 - the lower the ratio, the more uniform the heat output is across the ultrasound sound head.

A high ratio indicates some areas of the sound head will put out more heat than other areas creating “hot spots”.

44
Q 
If an ultrasound head has a BNR ratio of 7:1, how fast do you need to move the sound head to prevent hot spots in the tissue?
A. 2cm/sec
B. 3cm/sec
C. 4cm/sec
D. >4cm/sec
A

D. >4cm/sec to reduce chance of some tissue areas developing hot spots.

45
Q

For a patient w/ patellar tendonitis what would be the goal of using pulsed ultrasound?

A
  • Increase healing of the tissue
46
Q

What is ultrasound cavitation?

A
  • Expansion and compression of gas filled bubbles due to pressure changes
  • Used in non-thermal ultrasound
47
Q

T/F: Ultrasound cavitation cannot potentially damage the tissues.

A

False, it can cause damage.

PT Interventions II (4 decks)

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