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Physical Agents > Ultrasound > Flashcards

Ultrasound Flashcards

1
Q

What is US?

A

mechanical energy consisting of high frequency vibrations

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2
Q

An increase in frequency leads to a higher rate of absorption, therefore _ the depth of penetration.

A

Decreasing

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3
Q

How does US work?

A

reverse piezoelectric effect

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4
Q

What is the basis of the piezoelectric effect?

A

electrical energy (AC current) applied to lead zirconate titanate crystal in sound head which is converted to mechanical energy

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5
Q

What are the parameters of US?

A

frequency, intensity, duty cycle, ERA, BMR

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6
Q

What can happen with the US beam as its applied?

A

absorption, refraction, reflection

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7
Q

How do you minimize reflection of the sound energy?

A

deliver perpendicular to treatment surface

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8
Q

How does refraction occur?

A

as the beam travels from one medium to the other

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9
Q

What is spatial peak?

A

the maximum amplitude of the beam

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10
Q

What is spatial average?

A

the avg amplitude of the beam

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11
Q

What is BNR?

A

ratio of highest intensity in the field relative to the avg

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12
Q

What determines BNR?

A

Material used for piezoelectric transducer

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13
Q

What ratios do most machines have? and what is the best?

A

2:1 and 8:1, lower the better

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14
Q

What is attenuation?

A

the decrease in energy due to absorption, reflection, or refraction

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15
Q

Tissues with more attenuation will show what?

A

greater temperature rise

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16
Q

Attenuation values are higher for tissues with a higher what?

A

collagen content

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17
Q

What increase also increases attenuation?

A

frequency

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18
Q

How are attenuation and penetration related?

A

inversely

19
Q

What are the highest attenuations at 1 MHz?

A

bone, cartilage, tendon

20
Q

What are the types of effects US has?

A

mechanical and thermal

21
Q

What are the mechanical benefits of US?

A
  1. cavitation, microstreaming, acoustic streaming - movement of tissues at the cellular level
  2. increased intracellular Ca2+
  3. Promotes cell function
22
Q

What are the ways mechanical effects of US promote cell function?

A

a. mast cell degranulation
b. increased macrophage responsiveness
c. synthesis of fibroblasts
d. proteoglycan synthesis in chondrocytes
e. some evidence in fracture healing

23
Q

What are the thermal effects of US?

A

at 100% duty cycle:
@1C - increases metabolism and healing (13% for every 1 deg increase)
@2-3C - decreases pain and muscle spasm
@4+ - increases extensibility of collagen and scars, decreases joint stiffness

24
Q

What is the required for the effects at 4C to occur?

A

a 40-45C temp for at least 5 minutes

25
Q

What is the duty cycle?

A

time on/total time - reduced thermal effects as the time off allows heat to dissipate

26
Q

What is continuous duty cycle?

A

100%

27
Q

What effects occur at 100% duty cycle?

A

mechanical and thermal

28
Q

What are pulsed duty cycle?

A

anything under 100%

29
Q

What are the common options on US machines for pulsed duty cycle?

A

20 and 50%

30
Q

What effects occur at 50%?

A

Mostly mechical but some thermal

31
Q

What effects occur at 20%?

A

Mechanical only

32
Q

What are the frequency options and what are their MOAs?

A

1MHz for up to 5 cm, 3MHz for 1-2 cm

33
Q

What intensity should you use to increase temperature at a 1MHz frequency?

A

1.5 to 2.0 W/cm^2

34
Q

What intensity should you use to increase temperature at a 3MHz frequency?

A

0.5 W/cm^2

35
Q

What intensity should be selected for mechanical effects?

A

0.5 to 1.0 W/cm^2

36
Q

How soon should warmth be felt?

A

2-3 minutes

37
Q

What is the speed and shape of the motions of an US?

A

slow circles in a 1 cm/sec

38
Q

What is the size of the treatment area for US?

A

2-3x ERA (size of US head)

39
Q

What is the common duration of US?

A

5-10 minutes

40
Q

How soon should improvements be recognized?

A

2-3 treatments

41
Q

What are indications of US?

A

soft tissue shortening, pain control, dermal ulcers, tendon and ligament injuries, resorption of calcium deposits, bone Fx, CTS, Phonophoresis

42
Q

What are the precautions for US?

A

acute inflammation, epiphyseal plates, Fxs, breast implants

43
Q

What are the contraindications for US?

A

malignancy, pregnancy, CNS tissue, joint cement, plastic, pacemaker, thrombophlebitis, eyes and reproductive organs

Physical Agents (5 decks)

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