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Physical Agents > Ultrasound Quiz > Flashcards

Ultrasound Quiz Flashcards

1
Q

Most common diagnoses for which ultrasound is used

A

back
shoulder
knee
neck pain

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2
Q

what is ultrasound

A

high frequency mechanical waves delivering acoustic energy

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3
Q

why is an aqueous conducting gel needed?

A

ultrasonic energy can be dissipated more quickly in denser substances because they offer more resistance to molecular motion

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4
Q

when the wave is absorbed, what is the kinetic energy transformed into?

A

thermal energy

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5
Q

what is the angle of reflection dependent upon

A

the angle of incidence at the interface between tissues of differing densities

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6
Q

ultrasonic energy is more rapidly attenuated and converted to thermal energy in which tissues?

A

more dense tissues
tendons and ligaments
muscle

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7
Q

Attenuation of ultrasound beam in various tissues

A

Blood: 3%
Fat: 13%
Muscle: 24%
Blood Vessel: 32%
Skin: 39%
Tendon: 59%
Cartilage: 68%
Bone: 96%

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8
Q

KEY POINT! #1

A
  • More dense connective tissues, such as ligaments and tendons absorb US better than less dense tissues such as fat and muscle
  • Thus, US is more effective at heating more dense tissues than less dense tissues
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9
Q

where is the generator located and what is its key component?

A
  • It is located in the “big box”
  • Key Component: electrical oscillator that generates the high frequency alternating current that matches the intensity and frequency parameters of the applicator’s piezoelectric crystal
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10
Q

What is the US applicator composed of?

A
  • piezoelectric crystal
  • sound head
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11
Q

what is the reverse piezoelectric effect?

A
  • piezoelectric crystal is transversely compressed and expanded by sending an alternating electrical current through it
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12
Q

what is the area of the crystal that moves called?

A

effective radiating area

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13
Q

what is the range of frequencies?

A

0.75- 3.3 MHz
Lesser frequencies penetrate deeper
(3.3 means it is absorbing it 3.3 times faster)

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14
Q

what frequency is used to treat superficial structures such as exposed tendons and ligaments?

A

3 MHz

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15
Q

what frequency is used to treat deeper structures such as most muscles and fascia?

A

1 MHz

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16
Q

What is the depth of US penetration dependent on?

A

frequency

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17
Q

depth is inversely proportional to what

A

frequency

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18
Q

Spacial Average Intensity =

A

power (watts)/ ERA (crystal’s size in cm)

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19
Q

what is generally recommended regarding US intensity

A

use the lowest intensity possible to achieve the desired effect

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20
Q

is there a recommended dosage?

A

no

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21
Q

total energy =

A

intensity x sound head area x time = Joules (Watt/second)

22
Q

when keeping time and intensity the same, the bigger the sound head area…..

A

the bigger the dosage

23
Q

when utilizing pulsed US, what is reduced?

A

total energy level delivered

24
Q

Temporal (time) Average Intensity

A
  • used to describe lesser level of energy in pulsed US
25
Q

pulse duration

A

time that energy is flowing

26
Q

pulse period

A

combined time of energy flow and lack of flow

27
Q

What is the degree to which the total energy level is reduced dependent on?

A

duty cycle

28
Q

duty cycle equation

A

pulse duration/pulse period x 100

29
Q

What is BNR

A

how the non-uniformity of the crystal is addressed

30
Q

BNR equation

A

ratio between the spatial peak intensity and the spatial average intensity

31
Q

KEY POINT! #2

A

to minimize the chance of patient discomfort from hot spots, look for devices with low BNR
(but these are typically more expensive)

32
Q

in order to have a significant heating effect, what should the treatment area be?

A

2 x the ERA
- the bigger you go, the less heat you get

33
Q

KEY POINT #3

A
  • Apply US over too large of an area is the biggest mistake made by clinicians when using US
  • Area treated with US should not be larger than 4x ERA
  • More often than not, the ERA is less than the size of the sound head
34
Q

vigorous heating is defined as:

A

an increase of 7 degrees

35
Q

using 1 MHz, how long does it take to heat skeletal muscle to 6 degrees?

A

11 minutes

36
Q

KEY POINT #4

A
  • US units usually differ in the ERA of their applicators and may differ in other ways that affect efficiency of the treatment
  • Thus, no two US units can be considered to deliver the same treatment efficiency
  • The clinician must readjust the treatment protocols based upon the specific input and applicator being used
  • In this manner, each application of US represents a unique or individualized event
37
Q

when using US with a cotreatment, how long does the clinician have before the treated area cool?

A

4 to 5 mins

38
Q

can you determine the reponse a patient will have to US?

A

no - it varies a ton

39
Q

3 Important principles that should guide the application of US:

A
  1. The radiating waves of US must be kept perpendicular to the skin surface, thus the applicator must remain in contract with the skin surface
  2. A coupling medium must be used between the US applicator and the skin
  3. The applicator faceplate must be continually moved during the treatment
40
Q

3 different coupling mediums

A
  1. viscous aqueous gel
  2. water immersion
  3. gel pads
41
Q

two processes that produce nontermal effects

A

cavitation
acoustic streaming

42
Q

what is cavitation

A
  • cycles of compression and rarefactions of US exert forces on the cell membranes and tissue fluids, resulting in the formation and accumulation of thousands of gas bubbles under the influence of Bjerknes forces
  • formation of bubbles is called cavitation
43
Q

stable cavitation

A

cyclical expansion and contraction of gas bubbles in response to the acoustic cycles of compressions and rarefactions

44
Q

nonstable cavitation

A
  • may occur from an accumulation of large volume of gas bubbles that collapse
  • collapse is thought to be a cause for tissue damage
45
Q

what is acoustic streaming

A

the forward movement of fluid created by the force of energy of US waves
- no physiologic effects

46
Q

Key point #5 i think

A
  • a critical evaluation of the literature on US must consider the treatment dosage and size of the area treated, even if described
  • far too often, these parameters are poorly described or not described at all
  • this makes critical analysis of the literature challenging
47
Q

3 conditions that have been studied for using US for pain

A

myofascial pain syndrome
back pain
nonspecific shoulder disfunction

48
Q

what is phonophoresis

A

application of US to enhance the absorption of topical agents through the skin

49
Q

low intensity pulsed ultrasound

A
  • delivery of pulsed, medium frequency US at much lower intensity
  • delivers via a stationary applicator
  • primary use: bone fractures that show difficulty in healing and in speeding repair and bone tendon junctions
50
Q

low intensity therapeutic ultrasound

A
  • soft tissue healing
  • very low intensity pulsed US administered over 1 to 4 hr period using one or two stationary transducers (called SAM ultrasound applicators)
51
Q

non contact low frequency US

A
  • aerosolization of saline water with ow frequency US to cleanse and debride tissue
    MIST therapy

Physical Agents (11 decks)

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