Therapeutic Ultrasound (Part 2)

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Therapeutic Ultrasound(Part 2)

• By
• Ass.Prof.Dr.Gehan Mosad

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At the end of this lecture the student should be
able to
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Therapeutic Effects of US

• Ultrasound has a variety of biophysical effects
• A- Thermal effects
• B- Nonthermal effects
• The most effect of continuous US is on tissue
  temperature however, nonthermal effects can also
  occur with the use of continuous ultrasound.
• Pulsed US has mainly nonthermal effect, but it
  also produces a minimal sustained changes in
  tissues temperature, it probably does have a
  small brief heating effect during the on time of
  a pulse

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Thermal Effects of US

• As the energy within the sound waves is passed
  and absorbed by the tissues, it will cause
  oscillation of the molecules of that tissues
  about their mean position, clearly any increase
  in the molecular vibration will result in heat
  generation.
• The thermal effects of ultrasound are the same as
• those obtained with other heating modalities
  including
• acceleration of metabolic rate
• reduction or control of pain and muscle spasm
• alteration of nerve conduction velocity
• increased circulation
• increased soft tissue extensibility

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Thermal Effects of US (cont.)

• The structures heated by US are different from
  other heating modalities
• US reaches more deeply and heats smaller areas
  than most superficial heating agents.
• US also heats tissues with high US absorption
  coefficients more than those with low absorption
  coefficients tissues
• Tissue with high absorption coefficients are
  generally those with a high collagen content
  while tissues with low absorption coefficients
  generally have a high water content such as
  muscles.
• Thus
• US is particularly well-suited to heat such as
  tendons, ligaments joint capsules and
  fascia
• US is generally not the ideal physical agent for
  heating muscle tissue because muscle has a
  relatively low absorption coefficient also, most
  muscles are much larger than the available
  ultrasound transducers.

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Factors affecting amount of temperature increase

• The increase in tissue temperature produced by
  the absorption of ultrasound varies according to
• Type of tissue (absorption coefficient)
• Frequency
• Intensity
• Duration of the ultrasound.
• Blood circulating through the
• Reflection US waves in regions of soft
  tissue-bone interfaces
• Thus, higher temperatures are achieved
• in tissue with high collagen content
• with high frequency
• with high intensity
• with long duration

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Non-Thermal Effects of US

• When ultrasound is delivered in a pulsed mode,
  with a 20 duty cycle, the heat generated during
  the on time of the cycle is dispersed during the
  off time, resulting in no measurable net increase
  in temperature.
• Thus, pulsed US is used to produce nonthermal
  effects that including the following
• increase intracellular calcium,
• increase skin and cell membrane permeability
• increase mast cell degranulation,
• increase histamine release
• increase macrophage responsiveness,
• increase the rate of protein synthesis by
  fibroblast

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Non-Thermal Effects of US (cont.)

• Nonthermal effects of US are the result of the
  mechanical events produced by US, including,
  cavitations, acoustic streaming and micro
  massage.
• 1- Cavitation
• The formation of gas filled bubbles within the
  tissues body fluids during the phase of
  relaxation or rarefaction of US waves
• There are 2 types of cavitation
• Stable and non stables which have very different
  effects.

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Non-Thermal Effects of US (cont.)

• Stable cavitation
• It occurs at therapeutic doses of US. This
  is the formation growth of gas bubbles by
  accumulation of dissolved gas in the medium. The
  cavity acts to enhance the acoustic streaming
  phenomena as such would appear to be
  beneficial.
• Unstable (transient) cavitation
• It is the formation of bubbles at the low
  pressure part of the US cycle. These bubbles then
  collapse very quickly releasing a large amount of
  energy which is detrimental to tissue viability.
• This phenomenon occurs at higher US intensities
  with stationary head.
• Pulsing also reduces the risk of damage due to
  cavitation.

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Non-Thermal Effects of US (cont.)

• 2- Acoustic streaming
• It is a small scale eddying of fluids near a
  vibrating structure such as cell membranes the
  surface of stable cavitation gas bubble. Or, it
  is the steady, circular flow of cellular fluid
  induced by US.
• 3- Micro-massage (Microstreaming).
• It is a mechanical effect in which the sound
  wave traveling through medium will cause
  molecules to vibrate, possibly enhancing tissue
  fluid interchange.
• The result of combined effects of stable
  cavitation and acoustic streaming is the
  alteration of cell membrane permeability and
  increased cellular activity which in turn
  responsible for the therapeutic effect of US.

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Physiological Effects of Ultrasound

• 1- Effect on blood flow
• 2- Pain control
• 3- Effect on adhesion and scar tissue
• 4- Effect on wound healing
• 5- Effect on fracture healing

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Physiological Effects of Ultrasound (cont.)

• 1-Effect on blood flow
• Thermal effect.
• Alteration of cell permeability
• Histamine release

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Physiological Effects of Ultrasound (cont.)

• 2- Pain control
• Direct effect
• Increase pain threshold
• Decrease transmission of pain impulse along nerve
  fibers
• produce counterirritant effect (gate theory for
  pain inhibition)
• Indirect effect
• It results from the other effect of US which
  could lead to removing the source of pain such
  as
• removing waste products and edema reduction,
• improving tissues healing
• decrease muscle spasm
• breaking down adhesion.

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Physiological Effects of Ultrasound (cont.)

• 3-Effect on Adhesion and scar tissues
• Collagen has high US absorption coefficient
• The thermal effect of US lead to increasing
  extensibility of collagen rich tissues
• Thus US could be used prior to range of motion
  exercises and stretching exercises.
• Also, US is used to help improving the quality
  of the scar, resulting in a slightly stronger
  more elastic scar.

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Physiological Effects of Ultrasound (cont.)

• Effect on wound healing
• Pulsed ultrasound at low intensities (0.8 W/cm²)
  enhance healing of wound by
• stimulating collagen production by fibroblasts,
• increases the intracellular calcium ion levels
• improve the local blood supply
• encourage the growth of new capillaries
• stimulates the MYOFIBROBLASTS to contract,
  giving rapid initial wound strength.

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Physiological Effects of Ultrasound (cont.)

• Fracture healing
• The use of ultrasound accelerate the rate of
  fracture repair when US delivered at low
  intensity (0.03 W/cm²) at 1.5MHz pulsed at a
  ratio of 14. for 20 minutes.
• Using higher ultrasound doses(1 2 W/cm²) could
  have an adverse effect on the fracture healing
  process

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Indications of Ultrasound

• Muscle spasm
• Trigger areas
• Neuroma
• Scar tissue
• Joint contractures
• sympathetic nervous system disorders
• Acute and chronic and soft tissues injuries.
• Acute and chronic inflammation
• Wound and ulcers healing.
• Fracture healing.
• Neurogenic pain

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Contraindications of Ultrasound

• Pregnancy when used over the pelvic or lumbar
  area.
• Over areas of acute infection
• Areas of severely impaired circulation
• Over malignant tumors
• Over growing epiphyseal plates
• Areas around the eyes, heart, and genitals
• Tissues at risk of haemorrhage
• Venous thrombosis

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Precautions for US applications

• It is recommended to avoid using high doses of US
  or sufficient intensity in the following cases
• Acute inflammation
• Epiphyseal plates
• Fractures
• Breast implants
• The most common adverse effect is a burn, which
  may occur in the following conditions
• high-intensity, continuous ultrasound is applied.
• if a stationary application technique is used.
• in areas with impaired circulation or sensation
• with superficial bone

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Techniques of ultrasound applications

• a-Direct contact
• b. Water immersion
• c. Water bag
• d. Solid sterile gel as coupling

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a-Direct contact
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a-Direct contact
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Water immersion
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Ultrasound in conjunction with other physical
therapy agents
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Phonophoresis

• It is the application of ultrasound with a
  topical drug in order to facilitate transdermal
  drug delivery up to 6 cm.
• In the application of phonophoresis, the
  medication is in form of gel or cream.
• Preheating the area to increase the absorption of
  the medication
• Use only approved ultrasound transmission media.
• The direct coupling method is recommended
• Ensure that the skin is well moistened avoid
  areas of dry skin.
• Lower frequency and Pulsed US lead to deeper
  penetration.
• High intensity is recommended.
• The duration depends on the size of the area to
  be treated.

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Case study