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musculoskeletal rehabilitation > therapeutic ultrasound > Flashcards

therapeutic ultrasound Flashcards

1
Q

what is an ultrasound?

A
  • form of mechanical energy, which when applied to the body has both thermal and non- thermal effects
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2
Q

what is sound energy?

A
  • mechanical vibration at increasing frequency
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3
Q

what is the normal human sound range?

A
  • 16 Hz to 15-20,000 Hz
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4
Q

what is it called beyond the normal human sound range? what is it usually between?

A
  • beyond the limit is called ultrasound
  • usually between 1.0-3.0 MHz
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5
Q

what is 1MHz equal to?

A
  • 1 mil cycles per sec
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6
Q

what ultrasounds are available?

A
  • different sizes and types of ultrasounds are available
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7
Q

what are soundwaves? what do they consist of?

A
  • longitudinal waves consisting of compression and rarefaction
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8
Q

what do particles of a material do?

A
  • oscillates about a fixed point rather than move with the wave itself
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9
Q

what must there be for a pulsed shortwave?

A
  • must be a thermal component
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10
Q

what happens to the energy levels in a pulsed shortwave?

A
  • energy levels within the walls will diminish as energy is transferred to material
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11
Q

what is different for different tissues regarding pulsed shortwave?

A
  • energy absorption and attenuation
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12
Q

what is frequency?

A
  • number of times a particle experiences a complete compression/ refraction cycle in 1 second
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13
Q

what is a wavelength?

A
  • distance between two equivalent points on the waveform in the medium
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14
Q

what is the average tissue wavelength at 1MHz compared to 3MHz?

A
  • 1MHz= 1.5mm
  • 3MHz = 0.5mm
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15
Q

what is velocity?

A
  • speed that the wave travels through the medium
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16
Q

what is the saline velocity? is this the same for all tissues?

A
  • approx. 1500m sec-1
  • most tissues are similar
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17
Q

how do you work out velocity?- give the equation

A

velocity = frequency to wavelength
V = F. I

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18
Q

what is a transducer?

A
  • part of ultrasound containing crystal
  • converts electrical energy to sound
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19
Q

is US beam uniform? what does this mean?

A
  • US beam is not uniform
  • so changes depending on distance from transducer
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20
Q

what happens near treatment head?

A
  • when near field/ frenzel zone, significant interference
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21
Q

is energy in near field greater than the machine’s output?

A
  • energy in near field can be 12-15 times greater than the machine’s output
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22
Q

how do you work out the length of near field?

A
  • r^2/l
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23
Q

what does r stand for?

A
  • radius of transducer crystal
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24
Q

what does l stand for?

A
  • US wavelength
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25
Q

what is the zone beyond the near field known as? how is it described?

A
  • known as Fraunhofer zone
  • beam more uniform and divergent
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26
Q

what is beam nonuniformity ratio (BNR) ?

A
  • quality indictor of US applicators (transducers)
  • gives an indication of near field interference
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27
Q

what does beam nonuniformity ratio (BNR) numerically describe?

A
  • describes the ratio of intensity peaks to mean intensity
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27
Q

what does each tissue present? what is it determined by?

A
  • presents impedance to sound waves
  • determined by density and elasticity
27
Q

what is BNR for most?

A
  • BNR would be 4-6
28
Q

when does maximum energy transfer occur?

A
  • occurs when the impendance of adjacent media is similar
  • large differences = ^ reflection and reduced transmission of energy
29
Q

when does the most significant impedance difference occur?

A
  • occurs at steel/ air interface
30
Q

what is a coupling media?

A
  • suitable coupling medium e.g., gel, oil, cream or water is essential to minimise air gaps to reduce total reflection
31
Q

what should the coupling media be?

A
  • should be fluid (to fill up available spaces), viscous and allow for maximum absorption, attenuation and disturbance
32
Q

what media is preferred and why?

A
  • gel- based media preferred over oils and creams while water is a good alternative but lacks viscosity
33
Q

how do you avoid bacterial contamination?

A
  • treatment heads should be cleaned with an alcohol- based swab between treatments to reduce microbial transmission
34
Q

what happens when a US wave encounters a boundary at an angle of 90 degrees?

A
  • refraction occurs
  • changing the beam’s path
35
Q

why is pathway angled?

A
  • because beam through 2nd medium will not be the same as its path through original
36
Q

what is US energy absorption described as?

A
  • exponential
  • superficial tissues absorb more energy
37
Q

is there a point of complete absorption?

A
  • no but energy levels decrease with depth as a greater proportion of energy absorbed
38
Q

what is half value depth?

A
  • depth where half the surface energy is available
39
Q

what do half value depths vary by?

A
  • vary by tissue type and frequency
40
Q

what is the half value depth of 3MHz compared to 1MHz?

A
  • 3MHz= 2cm
  • 1MHz= 4cm
41
Q

what tissues absorb more effectively?

A
  • tissues with higher protein content e.g., ligaments, tendons, fascia absorb US more effectively that those with high water content e.g., blood, fat
42
Q

what is ranking done by?

A
  • ranking by absorption capacity
  • critical for clinical decision making
  • high collagen tissue particularly effective absorbers
43
Q

what limits the effectiveness of US energy?

A
  • cartilage and bone reflect much of the US energy
44
Q

what is more effective when implicating ultrasounds clinically?

A
  • targeting highly absorptive tissues is more effective than low absorption capacity
45
Q

what is a pulsed output? what is the common pulse ratios?

A
  • common pulse durations are 2ms with variable off periods
  • typical pulse ratios are 1: 1 and 1: 4
46
Q

what is a relevant factor in dosage calculations ?

A
  • proportion of time that the machine is on compared with off
47
Q

how is pulse ratio (duty cycle) different to pulse frequency?

A
  • if 1:4;
    duration at 2ms= on for 2ms and off for 8ms= 100Hz
    duration increased to 4ms= on for 2ms and off for 16ms= 50Hz
48
Q

what affects the number of cycles per second?

A
  • adjusting pulse duration
49
Q

what is the normal pulse time?

A
  • 2ms meaning 100 pulses of ultrasound energy delivered per second
50
Q

how does ultrasound help in tissue healing?

A
  • enhances tissue healing by speeding up recovery and improving repair quality
51
Q

what are the thermal effects of heating the tissue?

A
  • promotes hyperaemia
  • aids in chronic inflammation resolution
52
Q

what are non- thermal effects primarily attributed to?

A
  • cavitation
  • acoustic streaming
53
Q

what is cavitation?

A
  • involves the formation of gas- filled voids within tissues and body fluids
54
Q

what is stable cavitation?

A
  • formation of gas bubbles by accumulation of dissolved gas in the medium (approx 100cycles)
55
Q

what does stable cavitation enhance and promote ?

A
  • enhances acoustic streaming
  • promotes cellular activity
56
Q

what is unstable cavitation?

A
  • formation of bubbles at low pressure part so bubbles collapse very quickly
  • releasing large amounts of energy> potentially harmful to tissue viability
57
Q

what is acoustic streaming?

A
  • small scale fluid movement around a vibrating structure and surface of stable cavitation gas bubble
58
Q

what does acoustic streaming affect?

A
  • affects diffusion rates and membrane permeability
  • influences metabolic processes
59
Q

what permeability is altered and what does this cause due to acoustic streaming?

A
  • sodium ion permeability is altered
  • changes cell membrane potential so alteration in enzyme control mechanisms like protein synthesis
60
Q

what is micromassage?

A
  • mechanical effect where sound wave travelling causes molecules to vibrate
61
Q

what does micro massage enhance and effect?

A
  • enhances tissue fluid interchange
  • affects tissue mobility
62
Q

how does ultrasound aid inflammation stage?

A
  • stimulates mast cells, platelets, white blood cells and macrophages
  • act as inflammatory optimiser
63
Q

how does ultrasound aid proliferation stage?

A
  • positively influences fibroblasts, endothelial cells and myofibroblasts
64
Q

how does ultrasound aid remodelling stage?

A
  • improves collagen fibre orientation and transition from type III to type I collagen
65
Q

when are ultrasounds used?

A
  • fracture repair
  • wound healing
  • stress fracture diagnosis via pain response
  • chronic sinusitis
  • pain management
  • knee osteoarthritis
66
Q

what are the contraindications of ultrasound?

A
  • malignant tumour
  • pregnancy
  • CNS tissue
  • joint cement
  • plastic components
  • pacemaker
  • thrombophlebitis
  • eyes
  • reproductive organs
67
Q

what are the cautions of ultrasounds?

A
  • acute inflammation
  • epiphyseal plates
  • fractures
  • breast implants

musculoskeletal rehabilitation (12 decks)

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