ultrasound Flashcards
1
Q
ultrasound
A
- acoustic energy
- produce thermal/nonthermal physiologic effects
2
Q
ultrasound uses
A
- diagnosis
- destruction of tissue (bone, scar tissue, tumor)
- tissue healing
- raise tissue temp
- modulate pain
3
Q
effects of US
A
- increased rate of tissue repair
- wound healing
- increase blood flow
- increase tissue extensibility
- breakdown calcium deposits
- reduction pain & muscle spasm
- change cell membrane permeability
4
Q
high frequency sound waves produced
A
- relies on molecular collision for transmission
- causes vibration
- produces heat & mechanical energy
5
Q
transmission of US waves
A
- high frequencies require dense medium to travel
- sinusoidal waveform (wavelength, frequency, amplitude, velocity)
6
Q
longitudinal waves
A
- molecular displacement along direction (parallel) wave travels
- compression & rarefaction
- can trace in solids & liquids
7
Q
transverse waves
A
- molecules displaced in direction perpendicular to the direction the wave is moving
- only travel in solids
- when US strikes bone
8
Q
frequency
A
- .75-3MHz
- higher frequency - more focused beam
- rate of absorption increases as frequency increases
- low frequency - greater depth of penetration
- high frequency - greater absorption in superficial tissues
- 3MHz - superficial tissues, rapidly absorbed, 2cm, collimated beam
- 1MHz - deep tissues, 5cm, diverging beam
9
Q
velocity
A
- rate vibration/sound wave propagated through conducting medium
- directly related to density of material
- more dense - higher velocities
10
Q
attenuation
A
- decrease in waves intensity resulting from absorption, reflection, refraction of energy
- penetrates - tissue high in water content
- absorbed - tissue high in protein (where greatest heating potential)
- absorption increases - frequency increases - less energy transmitted to deeper tissues
11
Q
acoustic impedance
A
- sound wave encounters boundary/interface between different tissues
- determines amt energy reflected & amt transmitted to deeper tissues
- energy reflected - intensity of energy increases as meet new energy being transmitted
12
Q
reflection
A
- occurs when wave can’t pass through next density
- strikes obj & reverses direction away from material
13
Q
refaction
A
- bending of waves - change in the sped of a wave as it enters a medium of different intensity
- dense layer to less dense - speeds up
- occurs when passing through joints
14
Q
absorption
A
- occurs through medium collecting wave & changing it to kinetic energy
- any energy not absorbed/reflected by one tissue layer will continue to pass through the tissue until it strikes another density layer
- inverse relationship between penetration & absorption
- depends on protein content (collagen)
15
Q
transducer/soundhead
A
- alternative current flowing through piezoelectric crystal
- converts electrical energy to acoustic energy
16
Q
piezoelectric effect
A
- as electrical energy from generator reaches transducer - causes expansion/contraction of crystal
- conversion form electrical energy to acoustic energy to mechanical energy
17
Q
effective radiating area (ERA)
A
- area on sound head that produces US waves
- transducer & ERA - match diameter - maintain effective coupling
- center ERA - greater temp, energy output
- treatment area - 2/3x larger tan ERA
18
Q
depth of penetration
A
-rate of absorption - attenuation - increases as frequency increases
19
Q
collimated beam
A
- sound less divergent - concentrating energy in limited area
- produced by large diameter transducer
20
Q
near field
A
- zone of fluctuating US intensity
- beam closer to transducer (near field) varies in US intensity - as beam moves from transducer energy more consistent
- length near field= radius transducer/wavelength ultrasound
21
Q
beam non-uniformity ratio (BNR)
A
- amt variability intensity w/in US beam
- low ratio - uniform beam
- 1:1 optimal - usually 2:1-6:1
22
Q
amplitude
A
-magnitude of vibration in a wave (N/m squared)
23
Q
power
A
-total amt US energy in beam (W)
24
Q
intensity
A
- measure of rate at which energy being delivered per unit area (strength)
- types: spatial averaged intensity, spatial peak intensity, temporal peak intensity, temporal averaged intensity, spatial averaged temporal peak intensity
25
spatial-averaged intensity (SAI)
- intensity of US beam averaged over entire are of transducer
- calculated by dividing the power of the output by the ERA of transducer head
- ex: 10W through sound head ERA 5 - SAI 2W
- increasing size of transducer - decrease SAI
26
spatial peak intensity
-highest volume occurring w/in beam over time
27
temporal peak intensity
-maximum intensity during on period w/ pulsed US
28
temporal-averaged intensity (TAI)
-average power during both on & off periods
29
spatial-averageed temporal peak
- maximum intensity occurring in time of SAI
| - spatial average during single pulse
30
half layer value
- amt US energy produced by generator
| - describes depth at which 50% US energy has been absorbed
31
treatment duration
-depends on size of area being treated & therapeutic goals of treatment
32
ultrasound transfer through tissues
- US passes through soft tissues in form longitudinal waves, until it strikes bone - some energy reflected, rest converted into transverse waves
- when sound hits acoustical interface - some energy reflected or refracted
33
standing waves
- reflected wave meets incoming incident wave
| - increases intensity of energy
34
ultrasound application depends on:
- output desired (thermal changes in bodys tissues,produce non-thermal changes in bodes tissues)
- stage of tissue healing
- inflammatory stage
- therapeutic goals of treatment
- area of injury
35
continuous output
- sound intensity remains constant throughout treatment
- ultrasound produced 100% time
- effectively heat tissues >5cm deep
36
pulsed output
- intensity periodically interrupted w/no US energy being produced during off period
- decreases temporal average intensity
- ratio expressed % duty cycle
- closer to 100% - greater net thermal effects of treatment
- lower duty cycle produced greater proportions of non thermal effects
37
duty cycle
pulse length/ (pulse length + pulse interval) x 100
38
nonthermal effects
-changes w/in tissues resulting from the mechanical effect of ultrasonic energy
39
thermal effects
- changes w/in tissues as a direct results of US elevation of tissue temp
- traditional use for US
40
examples of thermal effects of US
- increase extensibility collagen fibers, tissue
- decrease joint stiffness
- reduce muscle spasm
- modulate pain
- increase blood flow
- mild inflammatory response
- increase sensory/motor nerve conduction velocity
- increase collagen deposition
- increase macrophage activity
- elevate tissue temp
- increase local metabolism
41
temperature increase
- for therapeutic effect heating - tissue temp elevated min 3-5min
- amt temp increase depends on: mode application, intensity&frequency output, vascularity & type of tissue, speed sound head moves
- mild - 1degC - mild inflammation & increase metabolic rate
- moderate - 2-3degC - decrease muscle spasm, pain, increase blood flow, reduce chronic inflammation
- vigorous - 3-5degC - tissue elongation, scar tissue reduction, inhibition sympathetic activity
42
sound waves heat tissue
-attenuation, absorption, scattering - creates friction between molecules - temp increase
43
primary advantage US
- tissues high in collagen may be selectively heated w/o causing sig temp change to skin/fat
- fluid filled tissues relatively transparent to US
44
examples of non-thermal effects of US
- increase cell membrane permeability
- altered rates diffusion across cell membrane
- increased vascular permeability
- secretion chemotactics
- increase blood flow
- increase fibroblast activity
- stimulate phagocytosis
- produce healthy granulation tissue
- synthesis protein
- reduce edema
- synthesis collagen
- diffusion ions
- tissue regeneration
- increase cavitation
- form strong, more deformable connective tissue
45
cavitation (non thermal effect US)
- formation gas-filled bubbles that expand & compress due to US induced pressure changes in tissue fluids
- stable - bubbles expand & contract in response to regularly repeated pressure changes over many acoustic cycles
- unstable - violent large excursions in bubble volume occur before implosion & collapse occur only after a few cycles
46
acoustical microstreaming (non thermal effect US)
- unidirectional movement of fluids along boundaries of cell membranes resulting form mechanical pressure wave in US field
- produces high-viscous stresses - alter cell membrane structure & function due to change in permeability & diffusion rates
- facilitates passage of calcium, potassium, sodium, other ions & metabolites into/outof cell
- occurs due to stable cavitation
47
pulsed US
- high intensity, short duration
| - trigger series physiological events that stimulate healing process
48
frequency treatment: acute conditions
- more frequent treatments over shorter period time
- low intensity/pulsed US 1/2x day for 6-8 days
- use until acute symptoms subside
49
frequency treatment: chronic conditions
- fewer treatments over longer period of time
| - alternating days
50
duration treatment
- typical: 5-10min
| - based on: size of treatment area, intensity, frequency, desired temp increase
51
coupling methods
- US can't pass through air
- ensure max energy transfer
- allow waves to pass out of transducer into tissues
- optimal medium - distilled water
52
coupling medium
- used to exclude air from the region between patient & transducer so ultrasound can get to area to be treated
- match impedance of transducer & slightly higher than skin
- low coefficient of absorption to min attenuation
- reamin free of air bubbles during treatment
- be viscous enough to be lubricant
53
direct contact
- actual contact between sound head & skin, w/ gel
- increase viscosity
- effective ness decreased: lot hair on body part, irregular shaped
54
immersion
- immerse in tub (plastic, ceramic, rubber) of water
- recommended: treatment area smaller than diameter of transducer, irregular w/bony prominences
- increase intensity by .5W/square cm (50%) - to account for attenuation caused by air & minerals in water
55
bladder technique
- water-filled balloon/surgical glove coated w/ coupling gel
| - conforms to irregularly shaped areas
56
moving transducer
- speed - 4cm/sec (BNR dependent)
- higher BNR - move transducer faster
- moving too rapidly - decrease total amt energy absorbed per unit area
- slow movement - evenly distributed sound waves throughout area
- pressure - .44-1.32 lbs
57
treatment area
2-3x larger ERA of transducer
58
acute stage injury
- continuous US - contraindicated
| - US delivered w/ low intensity & duty cycle
59
effect of US on injury response cycle
- blood flow
- tissue healing
- tissue stretching
- pain control
60
US effects on blood flow
- continuous US increase local blood flow, up to 45min after treatment
- due to: thermal effects, alteration of cell membrane permeability, dilation vessels
61
US effects on soft tissue healing& repair
- accelerated by thermal & non-thermal US (inflammatory phase)
- stimulate release of histamine from mast cells
- positively influences macrophage activity
- stimulates cell division
- low frequency US - enhances release of fibroblasts
- high frequency US - increases cells ability to synthesize & secrete fibroblasts
- acute stage - pulsed .5W/square cm 20% duty cycle 5min - continuous .1W/square cm
62
US effects on scar tissue & joint contracture
- increase mobility in mature scars
- increase tissue extensibility
- soften scar tissue
- preheating w/US & putting joint on stretch - increase greater residual tissue length w/less potential damage
- thermal effects - continuous moderate intensities .5-2W/square cm
63
US effects on stretching of connective tissue
- thermal effect - increase collagen-rich tissue extensibility
- utilize ROM exercises after continuous US
- scar tissues preferentially heated w/US
- temp target tissue - elevated 5degC
- place tissue on stretch during treatment - Drapers 'stretch window'
64
US effects on chronic inflammation
- decreases pain, tenderness & increases ROM
| - intensity 1-2W/square cm at 20% duty cycle - significantly enhances recovery in patients w/ epicondylitis
65
US effets on bone healing
- acceleration fracture reapir
- w/in 1st 2 wks - increase rate healing
- .5W/square cm, 20% duty cycle, 5min, 4x/wk
- US bone growth stimulators - pulsed, low intensity
66
US effects on assessing stress fractures
- continuous beam 1MHz, small transducer & water based coupling medium
- move transducer slowly over injured area while gradually increase intensity from 0-2W/square cm
- apply 1MHz continuous US in stationary mode to contralateral limb
67
US effects on pain control/reduction
- through direct effect energy has on PNS
- elevate threshold for activation of free nerve endings - thermal effects
- reduce pain - gating mechanism
- cell membrane permeability to sodium ions changed - altering electrical activity of nerve fiber
- increase nerve conduction velocity
68
US effects on absorption of Ca deposits
- help reduce inflammation surrounding Ca deposit
| - reduce pain, improve function
69
US effects on plantar warts
-.6W/square cm for 7-15min
70
US effects on placebo effect
-significant therapeutic physiological effects
71
US & hot packs
- heat - effective reduce muscle spasm & guarding, reduce pain
- treatment duration can be decreased when tissues preheated
- hot packs increase blood flow, creating less dense medium for transmission of US - attenuation & depth of penetration increased
72
US & electrical stimulation
- treatment of trigger points & painful areas
- US head acts as active electrode - delivers acoustic & electric energy
- electrical energy cause muscle contraction when sound head passes over trigger point, w/moderate increase in tissue temp
- both analgesic effects - reducing pain-spasm-pain-cycle
- improve circulation, relieve muscle spasm, decrease adhesion of scar tissue
73
determining output parameters of US requires knowledge of
- tissue involved
- depth of trauma
- nature & inflammatory state
- consideration of skin & tissues overlaying treatment area
74
US treatment precautions
-continuous US w/high spatial averaged temporal peak intensity - avoid acute & post acute conditions
-areas decreased sensation
-areas decreased circulation
-vascular problems, thrombophlebitis
-around eye
-over repro organs
during pregnancy
-around heart
-over malignant tumor
-epiphyseal area in youth
-metal implants
75
US indications
- acute & post acute conditions (non-thermal)
- soft tissue healing & repair
- scar tissue
- joint contracture
- acute/chronic inflammation
- increase extensibility collagen
- reduce muscle spasm
- pain modulation
- neuroma
- sympathetic nervous system disorders
- increase blood floe
- soft tissue repair
- increase protein synthesis
- tissue regeneration
- bone healing
- repair nonunion fractures
- inflammation associated w/myositits ossificans
- plantar warts
- myofascial trigger points
- spasticity
76
US treatment contraindications
- acute&post-acute conditions (thermal)
- decreased temp sensation
- decreased circulation
- vascular insufficiency
- thrombophlebitis
- eyes, heart, skull, genitals
- repro organs
- ischemic areas
- tendancy to hemorrhage
- over fracture site before healing complete
- pregnancy
- pacemaker
- malignant tumor
- epiphyseal areas in youth
- total joint replacement
- infection
- over SC, large nerve plexuses
- anesthetic areas
- active infection
- stress fracture sites
