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DPT 6120 > US > Flashcards

US Flashcards

1
Q

What is Ultrasound?

A

Form of mechanical energy consisting of high frequency vibrations >20,000 Hz.

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2
Q

What happens if you increase the frequency on US?

A

The higher the frequency , the higher the rate of US absorption (faster heating ) therefore the less depth of penetration

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3
Q

How does the US work?

A

works on reverse piezoelectric effect, the electrical energy (AC current) is applied to lead zirconate titanate crystal in sound head which is converted to mechanical energy.

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4
Q

What are the US parameters?

A

Intensity, Frequency, Duty Cycle, Effective radiating area (ERA)-cm^2, and Beam non- uniformity ration (BNR)

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5
Q

Which are some characteristics of the beam?

A

The beam may be absorbed (in tissues), reflected or refracted.

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6
Q

When does reflection occur?

A

Reflection is less if the sound energy is delivered perpendicular to treatment surface or interface

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7
Q

When does Refraction occur?

A

Occurs as the beam travels from one medium to the another (sound waves changing direction while still penetrating into deeper tissues)

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8
Q

What is the Spatial Peak?

A

The highest amplitude in the beam (the sound waves penetrating into the tissues)

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9
Q

What is the Spatial Average?

A

the average amplitude of the beam

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10
Q

What is the BNR?

A

The ratio of the highest intensity in the field (spatial peak) to the average intensity indicated on the machine ( spatial average) - its determined by the material used for piexoelectric inducer, Most machines have ratios between 3:1 and 8:1, we want the lowest ratio

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11
Q

What is the Attenuation coefficient?

A

Attenuation is the decrease in energy due to absorption, reflection, and refraction. (absorption accounts for 1/2 of attenuation.

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12
Q

Tissues with more attenuation will show a ____ temperature rise.

A

Greater

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13
Q

Attenuation values are higher for tissues with a ______ collagen content.

A

Higher

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14
Q

Attenuation increases as _______ of US increases.

A

Frequency

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15
Q

Attenuation coefficient is ______ related to penetration.

A

Inversely

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16
Q

What are the mechanical effects of US?

A
  • Cavitation, micro-streaming, acoustic streaming
  • Increased intracellular calcium
  • Promotes cell function
17
Q

How does US promote cell function?

A
  • Mast cell degranulation and histamine
  • Increased macrophage responsiveness
  • Synthesis in Fibroblasts
  • Proteoglycan synthesis in chondrocytes
  • Fracture healing= some evidence for promotion of fracture healing
18
Q

What are some of the thermal effects associated with TTR? 1 deg C

A

Increases metabolism and healing (roughly 13% increase in metabolism for every 1 deg C raise- or up to 2-3 fold increase for 10 deg C rise

19
Q

What are some of the thermal effects associated with TTR? 2-3 Deg C

A

Decreases pain and muscle spasm

20
Q

What are some of the thermal effects associated with TTR? 4 deg C or greater

A

Increases extensibility of collagen and scars, and decreases joint stiffness, a 40-45 degree centigrade temperature is required for at least 5 mins

21
Q

What is duty cycle?

A

Time on: time on+ time off; reduced thermal effects as the time off allows heat to dissipate during pulsed US at lower freq.

22
Q

What is continuous sound waves (thermal)?

A

100% Duty cycle; both thermal and mechanical effects

23
Q

What is Pulsed Sound Waves?

A

anything <100%

24
Q

What % duty cycles do most machines allow?

A

20% and 50%

25
Q

What happens during 20% duty cycle?

A

Mechanical effects only

26
Q

What happens during 50% duty cycle?

A

some thermal effects, but doesn’t have much use clinically

27
Q

When should you use a 1 MHz frequency?

A

tissues up to 5 cm deep

28
Q

When should you use a 3 MHz frequency?

A

tissues 1-2 cm deep

29
Q

What is intensity?

A

How much energy you are wanting to put into the tisuses

30
Q

With 1 MHz what intensity should you use?

A

1.5 to 2.0 W/cm^2

31
Q

With 3 MHZ what intensity should you use?

A

0.5 W/cm^2

32
Q

What intensity should you use if there is non- thermal effects desired?

A

Intensities of about 0.5 to 1.0 W/cm^2 have been shown to be beneficial

33
Q

What speed should you use the transducer head at?

A

Slow circles, move the head about 1 cm/sec, every circle overlaps last one by 1/2

34
Q

What should the size of the treatment area be?

A

Area covered should be about 2-3 times the size of the ERA in 5-10 mins

35
Q

When should you see the improvement with US?

A

should be detectable within 2-3 treatments, sometimes longer for more chronic problems

36
Q

What are the indications for US?

A
  • Soft tissue shortening
  • Pain control
  • Dermal Ulcers
  • Tendon and Ligament injuries
  • Resorption of calcium deposits
  • Bone fractures
  • carpal tunnel syndrome
  • Phonophoresis
  • Patient Values- talk to PT about past experiences
37
Q

What are the contraindications for US?

A
  • Malignancy
  • Pregnancy
  • CNS tissues
  • joint cement
  • Plastic
  • Pacemaker
  • Thrombophlebitis
  • Eyes and reproductive organs
38
Q

What are the Precautions with US?

A
  • Acute inflammation
  • Epiphyseal plates
  • Fractures
  • Breast Implants

DPT 6120 (5 decks)

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