3. Definition
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Ultrasound is a mechanical vibration at any
frequency above the audible sound range
Ultrasound therapy (UST) is the application of ultra
frequency sound waves (1 – 3MHZ) to tissues in
order to promote healing and reduce pain and
swelling.
Therapeutic Us used in physiotherapy ranges from
0.5 to 5MHZ but most us machine are set at 1MHZ
and/or 3MHZ
Classified as a deep heating modality
4. Production of ultrasound
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The inverse piezoelectric effect is used in production of
ultrasonic sound waves.
Examples of piezoelectic materials are quartz,barium
titanate and lead zirconate titanate (PZT).
Application of high frequency alternating current to the
PZT crystal of the transducer transforms the electrical
energy into vibratory sound wave (ultrasound)s
5. Transmission of US wave
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Through solid, liquid and gases in form of
compression and separation of molecule
Normally cylindrical and longitudinal in fashion
Velocity higher in materials of high density
Air 340 m/s, water 1410m/s, muscle 1540m/s, Bone
3500m/s.
6. Properties of ultrasound beam
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Reflection
Refraction Attenuation
Absorption
Passing through the tissue US energy is dissipated =
attenuation
Half Value Distance = 4cm for 1MHZ and 2cm for
3MHZ
Acoustic Impedance(Z)
7. Depth of penetration
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1MHZ= deeper tissues at
depth 3 to 5cm
3MHZ= superficial
Tissues at depth 1 to 2cm
Depth of Penetration is
inversely proportional to
frequency
Near and Far Field
Wave fonts from
different parts travel
different distances
causing interference
between adjacent fonts
8. Near and far field
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The near field also
known as the Fransel
zone is the convergent
region
The far field known as
the fraunhofer zone is
the divergent region
Length of Fresnel zone =
r2 / λ where r=radius of
transducer.
Therapeutic us utilizes
the near field
Frequency of US and
radius of transducer
need to be considered for
tissue depth above
6.5cm(shortest)
9. Coupling media
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Ultrasound waves are not transmitted by air, thus
some couplant which does transmit them must be
interposed
Unfortunately no couplant affords perfect
transmission & only a percentage of the original
intensity is transmitted to the patient.
Aquasonic gel 72.6%
Glycerol 67 %
Distilled water 59 %
Petroleum jelly 0 %
Air 0 %
10. Characteristics of a coupling media
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1. Acoustic impedance similar to tissue
2. High transmissivity for US
3. Low suceptibility to bubble formation
4. Chemically inactive in nature
5. A hypoallergic character
6. High viscosity
7. Cheap
8. Relative sterility
11. US beam parameters
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Mode type : continuous and pulsed. Pulsed Mark
Space(M:S) ratio: 1:1, 1:2, 1:4 etc.
Power: amount of acoustic energy per unit time (watts)
Intensity: power per unit area of the ultrasound head
(watts/cm2). Space average intensity and time
averaged/space average intensity(pulsed).
Frequency: number of compression-rarefaction cycles
per unit of time, usually expressed in cycles per second
(Hertz)
Effective radiating area (ERA): The area of the
transducer from which the US energy radiates
Duty cycle: The proportion of total treatment the
ultrasound was on
12. Depth of penetration
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Majority of the ultrasound generators used in
physiotherapy are set at a frequency of 1MHZ and/or
3MHZ.
The depth of penetration of ultrasound beam is
inversely proportional to the frequency
1MHZ ultrasound beam has a depth of penetration of
3-5cm and absorbed in deeper tissues
3MHZ ultrasound beam with a depth of penetration of
1-2cm and is absorbed in the superficial tissues
14. Protocols
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Preparation of the machine
Position
Inspect
Be assured of functionality
Bring all accessories closer:
• Aquasonic gel
• Cotton wool
• Methylated spirit
• Water in a bowl
Preparation of the patient
Inform your patient
Remove metals
Expose the Rx part
Remove hair if necessary
Wash or swab
Inspect the Rx part
Check for intact sensation
Demand co-operation
Set-up up the Rx
Secure pt.'s comfort and stability of Rx
part
Plug dead, supply and power on
Select Rx programme
Apply coupling media
Ensure the transducer is in contact with
the coupling media on the skin
Start now
Keeping asking how the pt.'s feels
15. protocols
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Termination
Return intensity to zero
Remove transducer
Cut the mains supply
Clean the skin and the
transducer
Inspect
Documentation
Date
Machine
Intensity
Frequency
Mode
duration
Coupulant
Region
Response of Rx`
16. Application
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Principles
Rx surface parallel to the skin
Even pressure maintained to
exclude air and balance
irregularities in sonic field
Transducer moved
continuously over the skin
surface
Rate of movement must be
slow enough to allow tissue to
deform and fast enough to
avoid hot spots
Pattern of movement- series
of overlapping parallel
strokes, circles or figure 8
Techniques of Application
1. Direct contact
2. Water bath: degased water
of comfortable temperature,
transducer held 1cm
parallel to the skin inside
the water keeping
3. Water bag
17. Dosage
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Factors to consider
Receny of injury
Depth of tissue
Nature of the lesion
Size of the area
Attenuation
Area of transducer
Acute conditions
Intensity: 0.25 or 0.5
watts/cm2
Time: 2-3minutes
Failure to improve progress to
0.8watts/cm2 or increase
time to 4 0r 5minutes
Chronic conditions
Start dose: 0.8watts/cm2 for
4minutes
Failure to improve progress to
1watts/cm2 for 4minutes,
1watts /cm2 for 6minutes, to
1.5watts/cm2 for 6minutes,
1.5watts/cm2 for 8minutes,
2watts/cm2 for 8minutes
Note: A dose of 2watts/cm2
for 8minutes is maximum
permitted
19. Physiological effects
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Chemical reaction
Ultrasound vibration
stimulate tissue to enhance
chemical reactions and
processes and ensure
circulation of necessary
elements and radicals for
recombination.
Biological responses
Increase membrane
permeability which
enhances transfer of fluid
and nutrients to tissues
Acoustic Streaming: is
unidirectional flow of
tissue components which
occurs particularly at the
cell membrane. Streaming
produce changes in the rate
of protein synthesis and
could thus have a role in
the stimulation of repair.
20. Physiological effects
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Mechanical responses
micro massage: cells are
alternately compressed and
then pulled further apart.
This increase mobility of
intracellular fluids and
thus helps to reduce
oedema.
Tendon extensibility:
ultrasound apparently
increases the extensibility
of tendons, muscles and
scar tissues.
Thermal effects: as
ultrasonic waves are
absorbed they are
converted to thermal
energy (heat)
21. Clinical application of US
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Soft tissue injuries
Oedema
Varicose ulcers
Pain control
Chronic rheumatoid and arthritic conitions
Tendon injuries
Resorption of calcium deposits
Bone fractures
Carpal tunnel syndrome
phonophoresis