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Phys Agents > Ultrasound > Flashcards

Ultrasound Flashcards

1
Q

What is frequency in US?

A

Number of vibrations/second

One million vibrations per second = 1 MegaHertz or 1 MHz

Use 1 to 3 in treatment

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2
Q

What is inside an US? What does it do?

A

Piezoelectric Crystals

Compressed mechanically, produce voltage

If voltage is passed through the crystal, it will compress or expand

US Trans contain such a crystal ,when plugged in, voltage causes the crystal to compress and expand

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3
Q

How is energy transmitted to tissue?

A

Sound energy is transmitted by vibration of molecules in the transducer via a medium (gel or water)

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4
Q

When is 1 MHz used?

A

Used for targets deeper than 2 cm (Up to 5 cm (2.5 inches) deep)

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5
Q

When is 3 MHz used?

A

Used for targets 1 to 2 cm deep

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6
Q

What are the two mode for ultrasound?

A

Continuous wave mode
Delivered w/o interruption

Pulsed wave mode
Interrupted by periods of no ultrasound wave transmission
Involves Duty Cycle

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7
Q

What is duty cycle?

A

Duty cycle is expressed as a percentage of sound wave transmission over time

Ex: time on/time on + time off

Duty cycle= On time/Total time

10 ms/20 ms = 50% duty cycle

(10ms/10ms+10ms)

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8
Q

What is wave intensity?

A

Intensity = amount of energy delievered to tissue and is measured in watts/cm2

Also known as the amplitude of the wave

Different areas of the crystal vibrate at different rates and therefore intensity is not uniform in the beam due to how is attached

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9
Q

Spatial Peak Intensity

A

Power of the beam at its greatest, located at center of soundhead

ERA = Effective Radiating Area; Sound is actually delivered in ERA

Size of sound head is slightly larger than ERA.

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10
Q

Spatial Average Intensity

A

Expression of the average power of the entire beam.

What you are actually putting on your patient

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11
Q

Beam Non-Uniformity Ratio

A

Ratio of spatial peak intensity/spatial average intensity

Smaller is better (and more expensive)

More even the energy disruption

Determined by the quality of the crystal and how transducer is structured

Ratios of 6:1 and less are acceptable ratios

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12
Q

Which of these two is a bad BNR?

A

The left! Bad Ratio, very high concentration in one spot

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13
Q

ERA – Effective Radiating Area

A

Actual cross sectional area of the US beam coming out of the US head

Treatment area should be maximum of about 2x the ERA (10 cm2)

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14
Q

Acoustic Impedance

A

Sound travels different through different mediums

Low impedance allows good transmission and little absorption

Blood and fluids have low impedance, bone has high impedance

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15
Q

Reflection and Refraction

A

If there is heterogeneity in tissue, reflection and refraction of sound waves will occur

Example: Boundary of muscle and bone will lead to significant reflection and refraction

Waves can interact with other waves due to reflection

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16
Q

What is a standing wave?

A

Sum and increase the energy at the interface.

Standing waves can be minimized by continuous movement of the sound head

Can be used to show sensitivity in stress fractures

17
Q

Attenuation

A

Refers to a decrease in sound energy as it travels through tissue

Can be reflected, refracted, or absorbed

18
Q

Physiologic Effects of Ultrasound

A

Thermal
Non Thermal

19
Q

Thermal Effects from US

A

Sound energy from US is absorbed by tissue causes friction at the molecular level which will produce heat

Pain modulation

Vasodilation

Decrease muscle tone

Decrease tissue viscosity

Known as a deep heating modality

Continuous mode for thermal effects

3 MHz heats up superficial quickly (5 min) while 1 MHz is longer more tissues (10 minutes)

Maximum of 4 degrees to increase extensibility

20
Q

Non Thermal Effects from US

A
  • Delivery of energy wihtout a significant rise in tissue temperature, typically requires a pulsed mode operation with a duty cycle equal to or less than 50%
  • Microstreaming or acoustic streaming
  • Cavitation
  • Unstable cavitation
21
Q

What is microstreaming?

A

Ions undergo small magnitude movement

Suggested that this alters permeability of cell membrane thereby facilitating cellular processes and promoting healing and growth

Gunk can be disrupted around other membrane and allow for tissue healing to occur as now things aren’t in the way

Limited research in support that it works

22
Q

What is cavitation?

A

Small gas bubbles that MIGHT be present in tissue fluid MAY undergo compression and expansion

Be very skeptical

23
Q

What is Unstable cavitation

A

Violent implosion and explosion of gas bubbles in tissue causing tissue destruction

May happen at high levels of US with no healing

Would never see in clinic

24
Q

US and Effect on Tissue Healing

A

Evidence is still lacking :/

25
Q

When you perform Thermal US on a patient do they receive both thermal and non thermal effects?

A

Yes

26
Q

Indications for US

A
  • Promotion of local tissue mobility (small or deep tissue)
  • Temporary pain relief (less pain signals going through)
  • Promotion of tissue healing
    • Thermal effects for vasodialation
    • Non-thermal effects for acute injuries, wounds, fractures
27
Q

Contraindications for US

A
  • Neither continuous nor pulsed US
    • Pregnancy (Low back or abdomen)
    • Cancer
    • Over electronic devices
    • Actively bleeding tissues or untreated hemorrhaging disorder
    • Deep Vein Thrombosis
    • Recent radiated tissues
    • myosisits ossificans
    • eyes
    • Anteriro neck/carotid sinus
    • reproductive organs
    • tissues with TB
  • Continuous
    • Cognitive impairment
    • infected tissues
    • Acute or exacerbation of chronic injury
    • Impaired circulation
    • Impaired sensation
    • Heat sensitive skin
    • Over implants containing cement or plastic components
28
Q

How large of an area should you do US on?

A

2x size of ERA

29
Q

What intensity is a good starting point for US

A

1.5

30
Q

How do you determine how long to US?

A

Time is based on how much time it will take for tissues to heat up

  • Factors:
    • Frequency
    • Tendon vs muscle
31
Q

How fast should you move the US head?

A

Slow, 4 cm/sec (approximately 1.5 inches

32
Q

Phonophoresis

A

Physically drive medication into tissue

No evidence to back this

33
Q

Precautions for US

A
  • Pulsed or continuous
    • Spinal cord or superficial peripheral nerves
    • Regenerating nerves
    • Active epiphysis (growing adolescents)
    • Fragile skin
  • Pulsed
    • Cement or plastic implants
    • impaired sensation
    • Impaired congition
    • Impaired circulation
    • heat sensitivity
    • infected tissues with drainage
    • Regenerating nerves
    • Acute or exacerbation of chronic injury

Phys Agents (10 decks)

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