2. Introduction
• Ultrasound is a type of sound waves that
transmit energy by alternately compressing
and rarefying material.
• Ultrasound is sound with a frequency greater
than 20,000 cycles per second[Hz].
• Human can hear sound with a frequency of 16
to 20,000Hz,sound with a greater than this is
known as ultrasound.
• Therapeutic ultrasound has a frequency
between 0.7 and 3.3 megahertz(MHz) to
maximize energy absorption at a depth of 3 to
5 cm of soft tissue.
3.
4. Production of Ultrasound
• Ultrasound is generated by applying a high –
frequency alternating electrical current to the
crystal in the transducer of an ultrasound unit.
• Piezoelectric effect – it is respond to the
alternating current by expanding and
contracting at the same frequency at which
the current changes polarity.
• when the crystal expands,it compresses the
material in front of it, and when it contracts,it
rarefies the material and this alternating
compression – rarefaction is the ultrasound
wave.
5. Contd.
• Piezoelectricity is the ability to generate
electricity in response to a mechanical force or
to change shape in response to an electrical
current.
• Commonly used crystals for piezoelectric
effect – natural quartz , synthetic plumbium
zirconium titanate (PZT) and barium titanate.
• Ultrasound transducers are usually made up
of PZT.
6.
7. Ultrasound Treatment Parameters
• Intensity
• Pulsed mark : space ratio
• Reflection of ultrasound
• Transmission of ultrasound
• Attenuation of ultrasound
• Ultrasonic fields
• Coupling media
• Duty Cycle
8. Intensity
• Space averaged intensity – where the average
intensity over a specified area is given, e.g.
watts per square centimeter.
• Time averaged /space averaged intensity – can
be used when the ultrasound is being applied
in a pulsed mode , and gives the average
intensity over the whole treatment time for a
specified area.
9. Pulsed mark : space ratio
When ultrasound is applied in its pulsed mode,
the ratio of the time on to time off should be
expressed.
10. Reflection of ultrasound
• An ultrasonic travelling through one medium
encounters another medium which will not
transmit it , reflection takes place.
• There will always be some reflection at each
interface that the ultrasound beam
encounters.
• Acoustic impedence which is ratio between
the reflected and transmitted at an interface.
11. Transmission of Ultrasound
• When the ultrasonic beam encounters an
interface between two media and is
transmitted, it may be refracted.
• Refraction mainly the deflection from its
original path.
12. Attenuation of Ultrasound
• Attenuation is gradual reduction in intensity of
ultrasonic beam once it has left the treatment
head.
• Factors that contribute to attenuation –
Absorption – ultrasound is absorbed by the
tissues and converted to heat at that point and
it contribute to the thermal effect of ultrasound.
• Scatter - when the normally cylindrical
ultrasonic beam is deflected from its path by
reflection at interfaces, bubbles or particles in
its path.
13. Contd.
• The overall effect of these two is such that the
ultrasonic beam is reduced in intensity the
deeper it passes.
• This gives rise to the expression “half-value
distance” which is depth of soft tissue that
reduces the ultrasound beam to half its
surface intensity.
• The half value distance for soft tissue varies
for 1 MHz and 3 MHz output and is 4 and 2 cm
respectively.
14. Ultrasonic Fields
• Depth of penetration and intensity of
ultrasonic beam in the division of the beam
into a near and a far field.
• The extent of the near field depends upon the
radius (r) of the transducer and the
wavelength (λ) of the ultrasound in the
medium.
• The depth of the near field can be calculated
using the formula r2/λ.
• As wavelength and frequency are inversely
related, the depth of the near field varies with
the frequency of ultrasound.
15.
16. Coupling Media
Ultrasonic waves are not transmitted by air, thus
some couplant which does transmit them must
be interposed between the treatment head
(transducer) and the patient’s skin.
17. Duty Cycle
• A continuous wave is on the sound intensity
remain constant, where as pulse wave is
intermitantly interupted.
• Pulse wave are further characterized by
specifying what fraction of time the sum is
present over one pulse period.
• This fraction is called duty cycle.
duty cycle =duration of pulse /pulse period
18. Testing the Apparatus
• Prior to any treatment it is sensible to check
that there is an output from the machine.
• This can be done by placing the treatment
head just below the water surface in a suitable
container and observing the disturbance
(ripples) which appears.
• The apparatus should be on and off with the
treatment head below the water.
• This, and similar methods, only indicate the
presence of an output but to quantity it, a
radiation.
21. Direct Contact Method
• If the surface to be treated is fairly regular
then a coupling medium is applied to the skin
in order to eliminate air between the skin and
the treatment head and transmit the
ultrasonic beam from the treatment head to
the tissues.
• Large area should be divided and each area
treated separately.
22. Water Bath Method
• When direct contact is not possible because of
irregular shape of part or because of
tenderness, a water bath may be used.
• As the part to be treated is immersed in water
this can only reasonably be applied to the
hand, ankle and foot.
23. Water Bag Method
Another method of applying ultrasound therapy
to irregular surface which cannot conventionally
be placed in a water bath is treated with a
plastic or rubber bag filled with water forming a
water cushion between the treatment head and
the skin.
24. Application
• The treatment head is moved continuously over
the surface while even pressure is maintained in
order to iron out irregularities in the sonic field.
• The rate of movement must be slow enough to
allow the tissues to deform and thus remain in
complete contact with rigid treatment head but
fast enough to prevent ‘hot spots’ developing
when using a high intensity treatment.
• The pattern of movement can be a series of
overlapping parallel strokes, circles or figures of
eight.
26. Dosage
This is the most controversial area when
discussing ultrasound because arguments about
whether pulsed or continuous modes should be
used and the intensities of ultrasound required
to produce beneficial effects.
27. Dosage in Acute condition
• In any acute conditions treatment applied
cautiously to prevent exacerbation of
symptoms.
• Initial stage - Low dose 0.25 to 0.5 Wcm–2
Time 2–3 minutes
• Progression unnecessary if condition improves
• Failure case 0.25 to 0.5 Wcm–2 Time 4–5
minutes or 0.8 Wcm–2 Time 2–3 minutes.
• It may also possible to select different M :S
pulse ratio and use: 1 : 7 for very acute 1 : 1
for less acute.
28. Dosage in Chronic Conditions
• Chronic condition may be treated with pulsed
or continuous mode.
• The maximum intensity of ultrasound which
should be used is that which produces mildly
perceptible warmth.
• This usually occurs around 2 W/cm2. Initially
low dose is tried. Intensity 0.8 W/cm2, time 4
minutes.
• Maximum dose of ultrasound: 2 Watts/cm2
for 8 minutes.
29. Physiological Effects of Ultrasound
• Thermal effects - As the ultrasound waves are
absorbed by the tissues they are converted into
heat. The amount of heat developed depends
upon:
1. Absorption of the tissues, e.g. protein absorbs
ultrasound more effectively and therefore produces
much heat.
2. The number of times the treatment head passes
over the part.
3. The efficiency of circulation through the
insonated tissues.
4. When using continuous ultrasound, the amount
of heat developed is directly proportional to the
intensity and duration of insonation.
30. Contd.
5. When using pulsed ultrasound there is less
thermal effect than with continuous and a mark
: space ratio 1 : 4 produces less heat than 1 : 1.
6. Reflection of ultrasound at a tissue interface
produces a concentration of heating effect at a
specific point.
31. Uses of Thermal Effects
• The local rise in temperature could be used to
accelerate healing.
• The extensibility of collagen is increased by
rise in temperature and so stretching of scars
or adhesions is easier following ultrasound.
• The thermal effect may also help reducing
pain.
32. Non – Thermal Effects
• Cavitation - oscillatory activity of highly
compressible bodies within the tissues such as
gas or vapour filled voids.
- Stable Cavitation - Stable cavitation occurs
when bubbles oscillate to and fro within the
ultrasonic pressure waves but remain intact.
- Microstreaming is the unidirectional
movement of fluids along the boundaries of the
cell. Due to microstreaming, permeability of cell
membrane and direction of movement of
molecules into the cells is influenced.
- Unstable Cavitation - This occurs when the
volume of the bubbles changes rapidly and then
collapse.
34. Contd.
• Mechanical or Micro - massage Effect - This
occurs where the longitudinal compression waves
of the ultrasound beam produces compression
and rarefaction of cells, and affect the movement
of tissue fluid in interstitial spaces. This can help
in reducing edema and pain.
• Biological Effects - Ultrasound can have some
useful effects in all three stages of repair.
1. Inflammatory: Ultrasound probably increases
the fragility of lysosome membrane, and thus
enhances the release of their contained enzymes.
These enzymes will help to clear the area of debris
and allow the next stage to occur.
35. Contd.
2. Proliferative: Fibroblasts and myofibroblasts
may have Ca++ ions driven into them by the
ultrasound. This increases their mobility and
encourages their movement toward the area of
repair. The fibroblasts are stimulated to produce
the collagen fibers to form scar and
myofibroblasts contract to pull the edges
together.
3. Remodeling: Ultrasound has been shown to
increase the tensile strength of the scar by
affecting the direction, strength and elasticity of
fibers which make up the scar easier.
36. Uses of Ultrasound
• Recent injuries and inflammation
• Scar tissue
• Chronic indurated edema
• Pain
• Dermal ulcers
• Surgical skin incisions
• Resorption of calcium deposits
• Bone fractures
38. Dangers
• Burns: If continuous beam is used and is
allowed to remain stationary, excess heat can
accumulate in the tissues and eventually leads
to burns.
• Cavitation: Especially unstable cavitation is
dangerous and has been described previously.
• Overdose: Excessive dose may cause an
exacerbation of symptoms.
39. Researches
1. Effect of therapeutic ultrasound on range of
motion and stretch pain.( Journal of
Physiotherapy2013)
method – 3 MHz ultrasound with an intensity of
1.0 W/cm2 and a duty cycle of 100% for 10 min.
result – the effect include the both thermal and
non – thermal effects on the range of motion and
stretch pain there is significant decrease in pain
after application of ultrasound.
2. Intensity dependent effect of pulsed and
continuous therapeutic ultrasound on endothelial
function.( International Journal of Therapy And
Rehabilitation 2019)
40. Contd.
method – 15 participants were evaluated over 2
days with different intensities and used both mode
of treatment, duty cycle 20% with 1 Mhz over
brachial artery for 5 minutes.
results – both modes ultrasound waveforms
promote endothelial – dependent vasodilation but
it is dose dependent increase in vasodilation at
intensities from 0.4 w/cm2 to 1.2 w/cm2.
3. Effects of therapeutic ultrasound and manual
physiotherapy in shoulder impingement syndrome
in volleyball players.(Journal of Islamabad Medical
and Dental College 2017)
41. Contd.
method – 5 min. of treatment, intensity 1 w/cm2 for
14 weeks with exercise session of 30 min and
frequency is 1 MHz.
results – ultrasound with the manual and exercises
therapy showed significant improvement at 14
weeks.
4.Efficacy of ultrasound massage therapy as an
adjuvant pain control modality in TMDs: A clinical
study(Journal of Indian Academy of Oral Medicine
& Radiology 2018)
method – ultrasound frequency was taken 1 MHz
with pulse setting 1:1 for 8 min. once a week for 4
comparative weeks
42. Contd.
US massage therapy in TM pain disorder is
effective and showed significant improvement in
pain as well as in mouth opening, before and
after treatment.
It is considered as a potent and independent
therapeutic modality in relieving TMJ pain
disorders.
![Introduction
• Ultrasound is a type of sound waves that
transmit energy by alternately compressing
and rarefying material.
• Ultrasound is sound with a frequency greater
than 20,000 cycles per second[Hz].
• Human can hear sound with a frequency of 16
to 20,000Hz,sound with a greater than this is
known as ultrasound.
• Therapeutic ultrasound has a frequency
between 0.7 and 3.3 megahertz(MHz) to
maximize energy absorption at a depth of 3 to
5 cm of soft tissue.](data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7)