Therapeutic ultrasound and application, physiotherapy based application of ultrasound, for basic understanding of ultrasound and its uses for therapeutic purpose.

1. ULTRASOUND
A Deep Thermal & Non-thermal
Mechanical Modality
Made by
SUNIL
MPT, (C.P.R.S )
J. M. I

2. Ultrasound
• May be used for diagnostic imaging,
therapeutic tissue healing, or tissue destruction
• Thermal & Non-thermal effects
• Can deliver medicine to subcutaneous tissues
(phonophoresis)

3. Ultrasound
• Sinusoidal waveform
– Therapeutic ultrasound waves range from 750,000
to 3,000,000 Hz (0.75 to 3 MHz)
• Displays properties of
– wavelength,
– frequency,
– Amplitude

4. Transducer
• A device that converts one form of energy to another
• Piezoelectric crystal: a crystal that produces (+) and (-)
electrical charges when it contracts or expands
– Crystal of quartz, barium titanate, lead zirconate, or titanate
housed within transducer
• Reverse (indirect) piezoelectric effect: occurs when an
alternating current is passed through a crystal resulting in
contraction & expansion of the crystal
– US is produced through the reverse piezoelectric effect
– Vibration of crystal results in high-frequency sound waves
• Fresnal zone (near field) – area of the ultrasound beam on
the transducer used for therapeutic purposes

5. Longitudinal vs. Transverse Waves
• Longitudinal waves – molecular displacement is
along direction in which waves travel (bungee
cord)
– Compression – regions of high molecular density
(molecules in high pressure areas compress)
– Rarefraction – regions of low molecular density
(molecules in low pressure areas expand)
• Transverse waves – molecular displacement in
direction perpendicular to wave (guitar string)

6. • Longitudinal waves – travel in solids & liquids
– Soft tissue – more like liquids
– US primarily travels as longitudinal wave
• Transverse waves – cannot pass through
fluids; found in the body only when
ultrasound strikes bone

7. Frequency
• Frequency: number of times an event occurs in
1 second; expressed in Hertz or pulses per
second
– Hertz: cycles per second
– Megahertz: 1,000,000 cycles per second
• In the U.S., we mainly use ultrasound frequencies of 1, 2
and 3 MHz
• 1 = low frequency; 3 = high frequency
• ↓ frequency = ↑ depth of penetration
• ↑ frequency = sound waves are absorbed in
more superficial tissues (3 MHz)

8. Velocity
• The speed of sound wave is directly related to the
density (↑ velocity = ↑ density)
• Denser & more rigid materials have a higher velocity
of transmission
• At 1 MHz, sound travels through soft tissue @ 1540
m/sec and 4000 m/sec through compact bone

9. Influences on the Transmission of Energy
• Reflection – occurs when the wave can’t pass
through the next density
• Refraction – is the bending of waves as a result
of a change in the speed of a wave as it enters a
medium with a different density
• Absorption – occurs by the tissue collecting the
wave’s energy

10. Attenuation
• Decrease in a wave’s intensity resulting from absorption,
reflection, & refraction
– ↑ as the frequency of US is ↑ because of molecular friction the waves
must overcome in order to pass through tissues
• US penetrates through tissue high in water content & is
absorbed in dense tissues high in protein
• ↑ Absorption = ↑ Frequency (3 MHz) , and
• ↑ Penetration = ↓ Absorption (1 MHz) , so
• ↑ Penetration = ↓ Frequency + ↓ Absorption (1 MHz)
• Tissues ↑ water content = low absorption rate (fat)
• Tissues ↑ protein content = high absorption rate (peripheral
nerve, bone)
– Muscle is in between both

11. Attenuation: Acoustic Impedance
• Determines amount of US energy reflected at tissue interfaces
– If acoustic impedance of the 2 materials forming the interface is the
same, all sound will be transmitted
– The larger the difference, the more energy is reflected & the less energy
that can enter the 2nd
medium
• US passing through air = almost all reflected (99%)
• US through fat = 1% reflected
• Both reflected/refracted @ m. interface
• Soft-tissue: bone interfaced = much reflected
• As US energy is reflected @ tissue interfaces with different
impedances, intensity is increased creating a Standing Wave (hot
spot)

12. • Effective Radiating Area (ERA): area of the sound
head that produces ultrasonic waves; expressed in
square centimeters (cm2
)
– Represents the portion of the head’s surface area that
produces US waves
– Measured 5 mm from face of sound head; represents all
areas producing more than 5% of max. power output
– Always lesser area than actual size of sound head
– Large diameter heads – column beam
– Small diameter heads – more divergent beam
– Low frequency (1 MHz) – diverge more than 3 MHz
• Treatment Duration: time for total treatment

13. Intensity Output & Power
• Power: measured in watts (W);
– amount of energy being produced by the transducer
• Intensity: strength of sound waves @ a given location
within the tissues being treated
• Spatial Average Intensity (SAI): amount of US
energy passing through the US head’s ERA;
– expressed in watts per square centimeter (W/cm2
)
(power/ERA)
– Changing head size affects power density (larger head results
in lower density)
– Limited to 3.0 W/cm2
of maximum output

14. Intensity Output & Power
• Spatial Average Temporal Peak Intensity (SATP):
average intensity during the “on” time of the pulse
– Output meter displays the SATP intensity
• Spatial Peak Intensity (SPI): max. output (power)
produced within an ultrasound beam
• Spatial Average Temporal Average Intensity (SATA) or
Temporal (time) Average Intensity:
– Power of US energy delivered to tissues over a given period of time
– Only meaningful for Pulsed US
– SAI x Duty Cycles

15. Beam Nonuniformity Ratio (BNR)
• Ratio between the spatial peak intensity (SPI)
to the average output as reported on the
unit’s meter
– The lower the BNR, the more uniform the beam is
– A BNR greater than 8:1 is unsafe
– Because of the existence of high-intensity areas in
the beam (hot spots), it is necessary to keep the
US head moving

16. Duty Cycle
• Percentage of time that US is actually being emitted
from the head
• Ratio between the US’s pulse length & pulse interval
when US is being delivered in the pulsed mode
– Pulse length = amount of time from the initial nonzero
charge to the return to a zero charge
– Pulse interval – amount of time between ultrasonic pulses
– Duty cycle = pulse length/(pulse length + pulse interval) x
100
– 100% duty cycle indicates a constant US output
– Low output produces nonthermal effects (20%)

17. Movement of the Transducer
• 4 cm2
/sec
• Remaining stationary can cause problems
• Moving too rapidly decreases the total amount of
energy absorbed per unit area
– May cause clinician to treat larger area and the desired
temps. May not be attained
• Slower strokes can be easier maintained
• If patient complains of pain or excessive heat, then
decrease intensity but increase time
• Apply constant pressure – not too much & not too
little

18. Coupling Agents
• Optimal agent – distilled H20 (.2% reflection)
• Modern units have a shut down mechanism if sound
head becomes too hot (Dynatron beeps; red lights on
Chattanoogas)
– Improperly coupled head causes ↑ temp.
• Types of agents:
– Direct
– H20 immersion
– Bladder
• Reduce amount of air bubbles

19. Direct Coupling
• Effectiveness is ↓ if body part is hair, irregular
shaped, or unclean
• Must maintain firm, constant pressure
• Various gels utilized

20. Water Immersion
• Used for odd shaped parts
• Place head approx. 1” away from part
• Operator’s hand should not be immersed No
metal on part or operator’s hand
• Ceramic tub is recommended
• If nondistilled H20 is used, intensity can be ↑ .5
w/cm2
because of air & minerals
• Don’t touch skin except to briefly sweep skin
when bubbles form

21. Bladder
• H20 filled balloon or plastic bag coated with
coupling gel
• Use on irregular shape part
• Place gel on skin, then place the bladder on
the part, and then place gel on bladder
• Make sure all air pockets are removed from
bladder

22. Indications
• Soft tissue healing & repair
• Joint contractures & scar tissue
• Muscle spasm
• Neuroma
• Trigger areas
• Warts
• Sympathetic nervous system disorders
• Postacute reduction of myositis ossificans
• Acute inflammatory conditions (pulsed)
• Has been shown to be ok to use following the
stopping of bleeding with an acute injury (pulsed)

23. Contraindications
• Acute conditions (continous output)
• Ischemic areas or impaired circulation areas
• Tendency to hemorrhage
• Around eyes, heart, skull, or genitals
• Over pelvic or lumbar areas in pregnant or
menstruating females
• Cancerous tumors
• Spinal cord or large nerve plexus in high doses
• Anesthetic areas
• Stress fracture sites or over fracture site before
healing is complete (continuous); epiphysis
• Acute infection

24. Thermal Effects
• ↑ blood flow
• ↑ sensory & motor nerve conduction velocity
• ↑ extensibility of structures (collagen); ↓ joint
stiffness
• ↑ collagen deposition
• ↑ macrophage activity
• Mild inflammatory response which may enhance
adhesion of leukocytes to damaged endothelial cells
• ↓ muscle spasm
• ↓ pain
• + all Nonthermal effects

25. Nonthermal Effects
• ↑ cell membrane permeability
• ↑ vascular permeability
• ↑ blood flow
• ↑ fibroblastic activity
• Altered rates of diffusion across cell membrane
• Secretion of chemotactics
• Stimulation of phagocytosis
• Production of granulation tissue
• Synthesis of protein
• ↓ edema
• Diffusion of ions
• Tissue regeneration
• Formation of stronger CT

26. Pulsed Ultrasound
• Stimulates phagocytosis (assists w/ ↓ of chronic
inflammation) & increases # of free radicals (↑ ionic
conductance on cell membrane)
• Cavitation: formation of gas bubbles that expand &
compress due to pressure changes in tissue fluids
– Stable – occurs when bubbles compress during the ↑-press.
peaks followed expansion of bubbles during ↓-press. troughs
– Unstable (transient) – compression of bubbles during ↑-press.
Peaks, but is followed by total collapse during trough (BAD!)

27. Pulsed Ultrasound
• Acoustical Streaming: stable cavitation leads this; one-
directional flow of tissue fluids, & is most marked
around cell membranes
– Facilitates passage of calcium potassium & other ions, etc.
in/out of cells
– Collagen synthesis, chemotactics secretion, ↑ update of
calcium in fibroblasts, ↑ fibroblastic activity
• Eddies (Eddy) – circular current of fluid often moving
against the main flow
– Flows around the cell membranes & its organelles
– Flow of bubbles in stream cause change in cell membrane
permeability

28. Clinical Applications – Soft Tissue
• Stimulates release of histamine from mast
cells
– May be due to cavitation & streaming
– ↑ transport of calcium ions across membrane that
stimulates histamine release
– Histamine attracts leukocytes, that clean up
debris, & monocytes that release chemotactic
agens & growth factors that stimulate fibroblasts
& endothelial cells to form a collagen-rich, well-
vascularized tissue

29. Clinical Applications – Soft Tissue & Plantar
Warts
• Pitting edema - ↑ temp. makes thick edema
liquefy thus promoting lymphatic drainage
• ↑ fibroblasts = stimulation of collagen
production = gives CT more strength
• Plantar Warts - 0.6 W/cm2
for 7-15 min.

30. Clinical Applications – Scar Tissue, Joint
Contracture, & Pain Reduction
• ↑ mobility of mature scar
• ↑ tissue extensibility
• Softens scar tissue
• ↑ pain threshold
• Stimulates large-diameter myelinated n. fibers
• ↑ n. conduction velocity

31. Clinical Applications
• Chronic Inflammation - Pulsed US has been
shown to be effective with ↓ pain & ↑ ROM
– 1.0 to 2.0 W/cm2
at 20% duty cycle
• Bone Healing – Pulsed US has been shown to
accelerate fracture repair
– 0.5 W/cm2
at 20% duty cycle for 5 min., 4x/wk
– Caution over epiphysis – may cause premature
closure

32. Treatment Duration & Area
• Length of time depends on the
– Size of area
– Output intensity
– Goals of treatment
– Frequency
• Area should be no larger than 2-3 times the surface area
of the sound head ERA
• If the area is large, it can divided into smaller treatment
zones
• When vigorous heating is desired, duration should be
10-12 min. for 1 MHz & 3-4 min. for 3 MHz
• Generally a 10-14 day treatment period

33. Thermal
Applications

35. Treatment Goal & Duration
• Adjust the intensity & time according to
specific outcome
• Desired temp.  ÷ /min. = treatment min.
– Ex. For 1.5 W/cm2
: 2°C ÷ .3°C = 6.67 min.

36. Phonophoresis
• US is used to deliver a medication via a safe, painless,
noninvasive technique
• Opens pathways to drive molecules into the tissues
• Not likely to damage or burn skin as with iontophoresis
• Usually introduces an anti-inflammatory drug
• Preheating the area may enhance delivery of
medication
– Encourages vascular absorption & distribution of meds.
• Some medications are poor conductors

37. Phonophoresis
• Factors affecting rate of medication diffusion
– Hydration – higher water content = skin more penetrable
– Age – better with younger ages
– Composition – better near hair follicles, sebaceous glands &
sweat ducts
– Vasularity – higher vascular areas are better
– Thickness – thinner skin is better
• Types of medications
– Corticosteroids – hydrocortisone, dexamethasone
– Salicylates -
– Anesthetics - lidocaine