PT1 EPAs > UNIT 2: Week 4 > Flashcards

UNIT 2: Week 4 Flashcards

Ultrasound (74 cards)

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1
Q

What is therapeutic ultrasound?

A
  • the delivery of high frequency inaudible mechanical energy (sound waves) to tissues using a transducer
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2
Q

Meaning of frequency in ultrasound

A
  • how often mechanical vibration is delivered to tissues via transducer
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3
Q

Most common frequencies for ultrasound

A

1 or 3 MHz

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4
Q

How does ultrasound work to deliver energy?

A
  • causes molecules to move (vibrate) within tissue
  • mechanical compression and rarefactions in the direction of the travel of wave
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5
Q

What is needed to transmit ultrasound energy?

A
  • coupling mechanisms, cant go through air
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6
Q

Different coupling agents

A
  • gel
  • water
  • oil
  • cream
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7
Q

Which types of tissues absorb more ultrasound energy?

A
  • dense tissues such as skin, fascia, fibrotic tissue, large nerve axons, tendons, joint capsule, ligament and periosteum (bone), cartilage
  • greater potential to heat
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8
Q

Which types of tissues absorb less ultrasound energy?

A
  • loose connective tissue, fat and muscle, nerve
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9
Q

What do low density tissues do with ultrasound energy?

A
  • do not absorb it, they transmit it
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10
Q

What are the ways in which ultrasound interacts with tissues?

A
  • oscillation of cells
  • deformation of cells
  • rotation of cells
  • expansion and contraction of gas bubbles in tissue fluid (cavitation)
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11
Q

What is Acoustic streaming?

A
  • movement of fluid around cells
  • facilitates movement of Ca2+ and K+ and other ions into and out of cells
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12
Q

What is stable cavitation?

A
  • creates microstreaming (small movements of fluid around the gas bubble)
  • exerts mechanical forces on surrounding cells which rotate and twist
  • facilitates movement of Ca2+ and K+ and other ions into and out of cells
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13
Q

What is unstable cavitation?

A
  • gas bubble implodes causing release of free radicals, pressure and pain
  • dont want this
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14
Q

Factors affecting ultrasound absorption

A
  1. Frequency of ultrasound (MHz)
  2. density of tissue
  3. Temp of tissue
  4. Technique
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15
Q

What does higher frequency mean for absorption?

A
  • more energy is absorbed superficially
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16
Q

At which depth is most of the energy absorbed with 3 MHz frequency?

A

1-2 cm

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17
Q

At which depth is most of the energy absorbed with 1 MHz frequency?

A

3-5 cm

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18
Q

How can we choose our frequency based on depth of tissues?

A
  • use 3 MHz when treating tissues up to 1.5 cm deep
  • use 1 MHz when treating tissues deeper than 1.5 cm
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19
Q

What happens when ultrasound energy is delivered to tissue?

A

Energy is…
- reflected
- refracted
- transmitted
- absorbed

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20
Q

Why is it important to use a coupling agent such as gel?

A
  • 99% of incident wave is reflected from metal to air but gel transmits energy through
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21
Q

How must we hold the ultrasound to ensure proper application?

A
  • perpendicular to tissues
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22
Q

What happens if we don’t hold the ultrasound perpendicular to tissues?

A
  • energy reflects and refracts (bends)
  • less energy delivered to target tissue
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23
Q

What does effective transmission of energy to tissues depend on?

A
  1. Continuity btwn crystal and metal plate
  2. Continuity btwn metal plate and tissue
  3. Coupling agent used btwn metal plata and tissue (need low acoustic impedence)
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24
Q

What is another important principle in applying ultrasound properly?

A
  • keep ultrasound head moving to avoid standing waves
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25
What are standing waves?
- when incident waves and reflected waves coincide and cause overheating, pain or tissue damage
26
How does temp of tissue affect ultrasound penetration?
- cooler tissues more dense than warmer - ultrasound penetration decreases when tissue temp is cooler than physiological temp - DO NOT COOL TISSUE prior to us application if you are trying to target deep tissues
27
How can intensity of ultrasound be described as?
1. A function of time (temporal distribution of energy) 2. a function of space (spatial distribution of energy)
28
How do we express intensity of energy of us in PT?
W/cm2
29
Two types of temporal intensities of ultrasound
1. Continuous 2. Pulsed
30
Continuous ultrasound
- 100% duty cycle - heat tissue - increase collagen extensibility `
31
Pulsed ultrasound
- 20% duty cycle - tissue healing - wound healing - bone healing - delivery of drug across tissue
32
What is the most commonly used pulsed ultrasound setting?
- 1:4 or 20% duty cycle *one unit on, four units off (2ms on, 8ms off)
33
Temporal peak intensity (TP)
- the maximum intensity delivered by US wave when it is on
34
Temporal average intensity (TA)
- average US intensity calculated over time when the pulses are delivered - TA = TP x duty cycle
35
Spatial peak intensity
- the max intensity delivered by the US unit over the beam
36
Spatial average intensity (SA)
- average intensity of the entire transducer
37
Are waves transmitted from US transducer head uniform?
NO
38
Goal of moving US around
- average out the intensity to make sure areas arent receiving too high or low low of energy
39
What do US units display?
- Spatial average temporal peak intensity (SATP) - treatment time - duty cycle - frequency
40
Ultrasound parameters to consider: frequency
- rate of expansion and contraction of piezoelectric material - measured in Hz - varies btwn 0.7-3.3 MHz, typically 1 or 3 MHz
41
Ultrasound parameters to consider: intensity
- amplitude - expressed in W/cm2 - varies btwn 0.1 W/cm2 - 3 W/cm2
42
Ultrasound parameters to consider: continuous vs pulsed
- expressed as a % of on time (duty cycle) or on:off ratio
43
Where do I document US treatment in SOAP notes?
- objective
44
How is ultrasound considered to be two separate modalities?
1. Thermal (continuous mode) - heating and cellular effects 2. Athermal (pulsed mode - cellular effects ONLY
45
What is the therapeutic heating range?
- 40-45 degrees celsius
46
Thermal effects of US treatment
- absorbed energy is converted to heat - absorption rate increases w increasing tissue density and with increasing frequency
47
How is heat gain modified by conduction and convection?
- bone could absorb heat and transmit it to other tissues
48
Physiological effects of thermal ultrasound
- heats through increased blood flow, local metabolism and extensibility of collagen tissue - sedation of sensory nerves (decreased pain) - reduce reflex activity and muscle spasm
49
When to use US vs a hot pack
- if you need to heat tissues more than 1 cm deep = US - very superficial = hot pack
50
Indications for use of thermal ultrasound
1. To decrease pain in conditions such as neuralgia, muscle guarding, muscle spasm, complex regional pain syndrome 2. To heat to greater than 40 degrees celsius for fibrotic conditions such as chronic inflammation, tendinopathies, adhesions, contractures, arthrosis, calcific tendonitis, hematoma
51
Indications for athermal US treatment
- tissue repair (sprains, strains, overuse injury, remodeling scar tissue etc.
52
Cellular effects of athermal ultrasound
- provides optimal environment for healing by stimulating mast cells, lysosomes, fibroblasts, endothelial cells and smooth muscle
53
Athermal ultrasound phonophoresis
- drug dissolved in a transmissive gel/cream which can transmit US
54
Optimal parameters for phonophoresis
- 1 MHz - pulsed 1:4 - 10 min duration for 10cm2 area
55
Athermal ultrasound for fracture repair
- low intensity pulsed ultrasound - stimulated bone healing - once daily for 20 min - 1.5 MHZ, 1000Hz, SATA 0.03 W/cm2
56
Athermal effects of US on collagen
- increased DNA synthesis - enhancement of type 1 and 3 fibres - improved organization/alignment of collagen fibres = increased extensibility and mobility of scar - increased tendon strength
57
Is US an effective modality?
YES
58
Treatment guidelines for athermal ultrasound: mode
- pulsed 1:4 (20% duty cycle)
59
Treatment guidelines for athermal ultrasound: intensity
1.0 W/cm2 (SATP) 0.2 W/cm2 (SATA)
60
Treatment guidelines for athermal ultrasound: frequency
3 MHz up to 1-2 cm deep 1 MHz for >2cm
61
Treatment guidelines for athermal ultrasound: treatment time
- 15 min application per 10-15 cm2 surface area
62
Treatment guidelines for athermal ultrasound: technique
- move transducer at a rate of 2-4cm/s
63
Treatment guidelines for athermal ultrasound: frequency (how often)
5x/week for 2-3 weeks then 3/week for 2-3 weeks *not realistic
64
Treatment guidelines for thermal ultrasound: intensity
0.8 - 2.0 W/cm2 (SATA) continuous US set according to body composition *start at 0.8 W/cm2, wait 2 min, if they dont report heat, increase by 0.1W/cm2 every min until heat is felt
65
Treatment guidelines for thermal ultrasound: frequency
1 MHz for heating tissue depth >1.6cm
66
Treatment guidelines for thermal ultrasound: treatment duration
10-15 min - max treatment area = 10cm2
67
Limitations of US in soft tissue healing
- loss of contact over contours - inefficient to treat areas >10cm2 - heating is difficult under water
68
Contraindications therapeutic ultrasound
1. on eyes 2. over abdominal area in pregnant women 3. on testes 4. over areas of known malignancy 5. over areas of known vascular insufficiency 6. over heart 7. over areas with lack of intact thermal sensation 8. over areas of acute infection or sepsis 9. over bleeding tissues 10. patients who are unreliable
69
Precautions of using therapeutic ultrasound
1. Ensure applicator is always moving 2. Use the lowest intensity that can produce a therapeutic response 3. Use caution over implanted electronic devices 4. Use caution using continuous ultrasound directly over superficial metal implants (pulsed is fine) 5. Avoid use over plastic joint implants
70
What to consider in the clinical planning for the application of EPAs (LFT POP)
L- location to be treated F- frequency per week T- timing in management plan P- parameters (dosage) O- objective measures P- progression
71
What category of EPA is US?
- both thermal and mechanical
72
Indications for use of thermal ultrasound: decrease pain
- neuralgia - muscle guarding - muscle spasm - complex regional pain syndrome
73
Indications for use of thermal ultrasound: heat to therapeutic temp
- chronic inflammation - tendinopathies - adhesions - contractures - arthrosis - calcific tendonitis - hematoma
74
Indications for use of athermal ultrasound: tissue repair
- sprains - strains - overuse injury - fracture - remodelling scar tissue - surgical scar - ulcers/wounds - calcific tendonitis
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