Therapeutic Ultrasound

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Therapeutic Ultrasound

• Jennifer Doherty-Restrepo, MS, LAT, ATC
• Entry-Level ATEP
• Therapeutic Modalities

2
Therapeutic Ultrasound

• One of the most widely used modalities in sports
  medicine
• _______________ inaudible, acoustic vibrations
  of high frequency that produce either thermal or
  non-thermal physiologic effects

3
Transmission of Acoustical Energy in Biological
Tissue

• Relies on _______________ for transmission
• Collisions cause molecular displacement and a
  wave of _______________
• Acoustic energy does ______ travel readily
  through space
• Must travel through a _______________
• Acoustic energy does not travel in a
  _______________
• Travels in waves in all directions
• Longitudinal and transverse waves

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Longitudinal Waves

• Primary waveform for travel in soft tissue
• Molecular displacement occurs along the
  ______________________________

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Transverse Waves

• Primary waveform for travel in ______
• Molecular displacement is _______________ to
  direction of wave propagation

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Frequency Of Wave Transmission

• Audible sound _______________ Ultrasound gt
  _______________
• Therapeutic Ultrasound _______________
  (1,000,000 cycles/sec)
• Penetration and absorption are ____________
  related
• Lower frequencies ______ depth of penetration
• Higher frequencies superficial ______________

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Velocity Of Transmission

• Directly related to tissue ______ (conducting
  medium)
• Higher density ______ velocity of transmission
• Lower density ______ velocity of transmission
• At a frequency of 1 MHz, ultrasound travels
  through
• Soft tissue at _______________
• Bone at _______________

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Attenuation

• _______ in energy intensity as the ultrasound
  wave is transmitted through various tissues
• ________ is due to absorption, dispersion, or
  scattering, which result from __________ and
  __________

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Penetration vs. Absorption

• _______________ relationship
• Absorption increases as frequency __________
• Tissues high in water content _________
  absorption
• Blood
• Tissues high in protein content ________
  absorption
• Bone, nerves, muscles, and fat

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Ultrasound at Tissue Interfaces

• Some acoustic energy scatters due to reflection
  and refraction
• ____________________ determines the amount
  energy reflected or transmitted at tissue
  interfaces
• _______________ X _______________
• If the acoustic impedance is equal at the tissue
  interface, energy will be _______________
• The larger the difference in acoustic impedance
  at the tissue interface, the more energy is
  _______________

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Acoustic Impedance

• Transducer - Air interface energy is completely
  _______________
• Through fat energy is transmitted
• _________________ energy is reflected and
  refracted
• Soft tissue - Bone interface energy is
  _______________
• Creates standing waves or hot spots

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Therapeutic Ultrasound Generators

• High frequency electrical generator connected
  through an oscillator circuit and a transformer
  via a coaxial cable to a transducer housed within
  an insulated applicator

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Ultrasound Generator
Electrical Output Mechanical Vibration Acoustic
Soundwave Absorbed In The Tissues
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Therapeutic Ultrasound Generator Control Panel

• Timer
• Power meter
• Intensity control
• _______________
• Duty cycle switch
• _______________
• Selector switch for continuous or pulsed
• Automatic shutoff if transducer overheats

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Transducer

• AKA
• _______________, or
• _______________
• Not interchangeable
• Piezoelectric crystal
• Quartz
• Synthetic ceramic crystal
• Converts ____________ energy to _____ energy
  through mechanical deformation

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Piezoelectric Effect

• When an alternating current generated at the same
  frequency as the crystal resonance is passed
  through the peizoelectric crystal, it will
  ________ and _______________
  
  
  
  
  
• Direct Effect - An electrical voltage is
  generated when the crystal expands and compresses

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Piezoelectric Effect

• ____________ generation of electrical voltage
  across the crystal when it is expanded or
  compressed
• __________________________ the alternating
  current moving through the crystal reverses its
  _______ as it expands and compresses resulting in
  vibration of the crystal at the frequency of the
  electrical oscillation
• This produces the desired therapeutic ultrasound
  frequency

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Effective Radiating Area (ERA)

• The portion of the transducer surface that
  actually produces the _______________
• Dependent on the __________ of the crystal
• Ideally, the surface area of the crystal nearly
  matches the diameter of the transducer surface
• Acoustic energy is contained in a ________
  ___________ beam that is roughly the same
  diameter of the transducer

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Frequency of Therapeutic Ultrasound

• Frequency number of wave cycles completed each
  _______________
• Frequency range of therapeutic ultrasound is
  _______________
• Most generators produce either 1.0 or 3.0 MHz

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Frequency of Therapeutic Ultrasound

• Depth of penetration is __________________ not
  intensity dependent
• 1 MHz deep heat
• _______________
• 3 MHz superficial heat
• _______________

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The Ultrasound Beam

• Concentrates energy in a limited area
• Larger transducer more ____________ _________
  beam
• Smaller transducer more _________ beam
• 1 MHz frequency more divergent than 3 MHz
  frequency

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Ultrasound Beam

• Near field
• Distribution of energy is _______________
• Area near transducer
• Non-uniformity due to differences in acoustic
  pressure created by the waves emitted from the
  transducer

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Ultrasound Beam

• Point of Maximum Acoustic Intensity
• As acoustic waves move ________ from transducer,
  they become indistinguishable and arrive at a
  certain point simultaneously

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Ultrasound Beam

• Far Field
• Waves travel beyond the point of maximum acoustic
  intensity
• Energy is more _____ ___________ and the beam
  becomes more divergent

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Beam Nonuniformity Ratio (BNR)

• Indicates the amount of ______________ in
  intensity within the ultrasound beam
• Determined by the highest intensity found in the
  ultrasound beam relative to the average intensity
  across the transducer
• Ideal BNR would be _______________
• Typical BNR _______________
• Maximal point of intensity 6 W/cm2
• Average output of intensity across transducer 1
  W/cm2

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Beam Nonuniformity Ratio (BNR)

• _____________ more even the intensity
• Less risk of developing hot spots
• _______________ higher nonuniformity
• Must move transducer faster throughout treatment
  to avoid hot spots
• Manufacturers must report the BNR
• Better generators have a ______ BNR, thus
  providing more even intensity throughout the field

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Pulsed vs. Continuous Ultrasound

• Continuous Ultrasound
• Ultrasound intensity remains constant over time
• Ultrasound energy produced ________ of the time

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Pulsed vs. Continuous Ultrasound

• Pulsed
• Ultrasound intensity is interrupted with no
  energy produced during the off time
• Average intensity of output over time is _________

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Pulsed Ultrasound and Duty Cycle

• Duty Cycle
• Percentage of time that ultrasound is being
  generated (pulse duration) over one pulse period
• Pulse period markspace ratio
• Duty Cycle duration of pulse (on time)
  x100 pulse
  period (on time off time)
• Duty Cycle may be set to 20 or 50
• Total amount of energy delivered would be only
  20 or 50 of the energy delivered if a
  continuous ultrasound wave was being used

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Amplitude

• May be defined 3 ways
• Magnitude of vibration in an ultrasound wave
• Movement of particles in the medium through which
  the ultrasound wave travels
• Measured in units of distance (____________)
• Vibration in pressure found along the ultrasound
  wave
• Measured in units of pressure (______________)

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Power vs. Intensity

• Both power and intensity are unevenly distributed
  in the ultrasound beam
• ______ total amount of ultrasound energy in the
  beam
• Measured in watts
• _______ measure of the rate at which energy is
  being delivered per unit area

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Intensity

• Spatial Average Intensity intensity of
  ultrasound beam averaged over the ______
  _______________
• Measured in W/cm2
• Power output in watts ERA of
  transducer in cm2
• Example
• 6 watts 1.5 W/cm2 4 cm2

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Intensity

• Spatial Peak Intensity _________ value
  occurring with the beam over time
• Therapeutic ultrasound maximum intensities range
  between ___ and ___ W/cm2
• Temporal Peak Intensity __________ intensity
  during the __ period with pulsed ultrasound
• Measured in W/cm2

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Intensity

• Temporal-averaged Intensity
• Only important with ___________ ultrasound
• Calculated by averaging the power during both the
  on and off periods (mean on/off intensity)
• Intensity settings on ultrasound generators may
  indicate _________________________ while others
  indicate ______________________

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Intensity

• There are no specific guidelines which dictate
  specific intensities that should be used during
  treatment
• Recommendation use the _______ intensity at the
  _________ frequency which transmits energy to a
  specific tissue to achieve a desired therapeutic
  effect
• Any adjustment in the intensity must be countered
  with an adjustment in _______________
• Treatments are temperature dependent, not time
  dependent

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Physiologic Effects of Ultrasound
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Thermal vs. Non-Thermal Effects

• Thermal effects
• Tissue heating
• Non-Thermal effects
• Tissue repair at the cellular level
• Thermal effects occur whenever the spatial
  average intensity is gt _______________
• Whenever there is a thermal effect there will
  always be a non-thermal effect

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Thermal vs. Non-Thermal Effects

• To elicit thermal therapeutic effects, tissue
  temperature must be raised to a level of 40-45C
  for a minimum of ___ minutes
• Baseline muscle temperature is _________
• Mild heating temperature ? of _____
• ? metabolism healing and healing
• Moderate heating temperature ? of ______
• ? pain and muscle spasm
• Vigorous heating temperature ? of ____
• ? extensibility of collagen and ? joint stiffness

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Thermal Effects of Ultrasound

• Increased collagen extensibility
• ________ blood flow
• ________ pain
• Reduction of muscle spasm
• ________ joint stiffness
• Reduction of _______________

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Ultrasound Rate of Heating Per Minute
Intensity W/cm2 1MHz 3MHz
0.5 .04C .3C 1.0
.2C .6C 1.5 .3C
.9C 2.0 .4C
1.4C

• At an intensity of 1.5 W/cm2 with a frequency of
  1MHz, an ultrasound treatment would require a
  minimum of 10 minutes to reach vigorous heating

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Ultrasound Rate of Heating Per Minute
Intensity W/cm2 1MHz 3MHz
0.5 .04C .3C 1.0
.2C .6C 1.5 .3C
.9C 2.0 .4C
1.4C

• At an intensity of 1.5 W/cm2 with a frequency of
  3 MHz, an ultrasound treatment would require only
  slightly more than 3 minutes to reach vigorous
  heating

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Non-Thermal Effects of Ultrasound

• ________ fibroblastic activity
• ________ protein synthesis
• Tissue _______________
• Reduction of __________
• Bone healing
• Pain modulation

All of these Non-Thermal Physiologic Effects of
Ultrasound Occur Through Acoustic Microstreaming
and/or Cavitation
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Acoustic Microstreaming

• Unidirectional flow of fluids along the cell
  membrane interface resulting from mechanical
  pressure waves in an ultrasonic field
• Alters cell membrane permeability to ______ and
  ________ ions important in the healing process

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Cavitation

• Formation of gas-filled bubbles that expand and
  compress due to ultrasonically induced pressure
  changes in tissue fluids

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Cavitation

• _______________
• Results in an increased fluid flow around these
  bubbles
• _______________
• Results in violent large excursions in bubble
  volume with collapse creating increased pressure
  and temperatures that can cause tissue damage

Therapeutic benefits are derived only from stable
cavitation
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Non-Thermal Effects of Ultrasound

• Can be maximized while minimizing the thermal
  effects by
• Using a ____________________ of
  0.1-0.2 W/cm2 with continuous ultrasound
• Setting duty cycle at ________ at intensity of
  1 W/cm2
• Setting duty cycle at ________ at intensity of
  0.4 W/cm2

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Techniques of Application
48
Frequency of Treatment

• Acute conditions require more frequent treatments
  over a _________ period of time
• 2 treatments/day for _______ days
• Chronic conditions require fewer treatments over
  a _______ period of time
• Alternating days for ________ treatments
• Controversy
• Limit treatments to a total of 14
• Continue treatments if there is improvement

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Duration of Treatment

• Considerations for determining Tx time
• Size of the area to be treated
• Intensity of treatment
• Frequency
• Treatment goals
• Thermal vs. non-thermal effects

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Size of the Treatment Area

• Should be ___ times larger than the ERA of the
  crystal in the transducer
• If the treatment area is larger than 2-3 times
  the ERA, other modalities should be considered
• _______________, _______________, or
  _______________

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Intensity

• Recommendations for specific intensities make
  little sense
• Ultrasound intensity should be adjusted to
  _______ ____________
• Increase intensity to the point where the patient
  feels _______, then decrease the intensity
  slightly to elicit general heating in the
  treatment area
• If you decrease intensity during treatment you
  should increase _______________
• Ultrasound treatments should be temperature
  dependent, not time dependent

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Frequency

• Determines _______________
• Determines _______________
• Energy produced at 3 MHz is absorbed 3 times
  faster than that produced from 1 MHz ultrasound
• Results in faster heating
• Reduce 3 MHz treatment durations by _________

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Coupling Methods

• Greatest amount of energy reflection occurs at
  the _______________
• Reduce amount of energy reflection by holding
  transducer ____________ (90 angle) to treatment
  area
• Coupling mediums further _________ reflection
• _______________ substance used to decrease
  acoustical impedance at the air-tissue interface
• Maximize contact with the tissue to facilitate
  passage of ultrasound energy
• Include gel, water, mineral oil, distilled water,
  glycerin, analgesic creams

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Direct Contact

• Transducer should be small enough to treat the
  injured area
• Gel should be applied liberally
• Heating gel does not increase the effectiveness
  of the treatment

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Immersion Technique

• Good for treating irregular surfaces
• A plastic, ceramic, or rubber basin
  should be used
• Tap water is useful as a coupling medium
• Transducer should move ______ to the surface at a
  distance of _________cm from the treatment area
• Air bubbles should be wiped away

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Bladder technique

• Good for treating irregular surfaces
• Uses a balloon filled with water
• Both sides of the balloon should be liberally
  coated with a _______________

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Moving The Transducer

• Applicator should be moved at a rate of
  _______________
• An ultrasound generator with a low BNR allows for
  ________ transducer movement
• An ultrasound generator with a high BNR may cause
  unstable ___________ and hot spots if the
  transducer is moved ______ _________

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Clinical Applications For Ultrasound

• Ultrasound is recognized clinically as an
  effective and widely used modality in the
  treatment of soft tissue and boney lesions
• There is relatively little documented, data-based
  evidence concerning its efficacy
• Most of the available data-based research is
  unequivocal

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Soft Tissue Healing and Repair

• During the __________________________ of healing,
  stable cavitation and _______________ increase
  the transport of calcium across cell membranes,
  thus releasing histamine
• Histamine stimulates
• ___________ to clean up the injured area
• ___________ to produce collagen (Dyson, 1985,
  1987)

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Scar Tissue and Joint Contracture

• Increased tissue temperature causes an increase
  in elasticity and a ___________ in viscocity of
  collagen fibers (Ziskin, 1984)
• Increased tissue temperature ___________ mobility
  in mature scar tissue (Gann, 1991)

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Chronic Inflammation

• Few clinical or experimental studies have
  observed the effects of ultrasound treatment on
  chronic inflammation
• Ultrasound does seem to be effective for
  increasing blood flow to the treatment area,
  which may facilitate the healing process and
  reduce pain (Downing, 1986)

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Bone Healing

• Ultrasound ___________ fracture repair
• (Dyson, 1982, Pilla et al., 1990)
• Ultrasound given to an __________ fracture during
  cartilage formation may cause cartilage
  proliferation and delay union
• (Dyson, 1989)
• No effect on _______________, but may help reduce
  surrounding inflammation
• (Ziskin, 1990)
• Not effective in detecting _______________

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Pain Reduction

• Ultrasound treatments are not used specifically
  for pain modulation
• Ultrasound may increase the ___________
  ____________ of free nerve endings
• (McDiarmid, 1987)
• Superficial heating may effect gating of pain
  impulses - _______________
• (Williams et al. 1987)
• Increased nerve conduction velocity creates a
  _______________ effect
• (Kitchen, 1990)

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Placebo Effects

• A number of studies have demonstrated a placebo
  effect in patients using ultrasound
• (Lundeberg, 1988, Dyson, 1987, Hashish et al.,
  1986)

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Phonophoresis

• Ultrasound energy used to drive topical
  application of selected medications into the
  tissues
• _______________
• Cortisol
• Salicylates
• Dexamethasone
• _______________
• Lidocaine

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Phonophoresis

• ___________ effects of ultrasound increase tissue
  permeability and acoustic pressure drives
  molecules into the tissue
• Effectiveness of phonophoresis is debatable
• Early studies demonstrated effective penetration
• (Griffin, 1982, Kleinkort, 1975)
• More recent studies show ineffectiveness
• (Oziomek et al, 1991, Benson et al., 1989)

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Ultrasound and Other Modalities

• US and Hot Packs _______________
• US and Cold Packs _______________
• Cooling the tissues does not facilitate an
  increase in temperature (Remmington 1994, Draper,
  1995)
• Analgesic effects of ice can interfere with
  perception of heating
• Pulsed US may be beneficial during
  Inflammatory-Response Phase of healing
• US and E-Stim _______________
• Effective in treating myofascial trigger points
  when used in combination with stretching
  (Girardi, et al. 1984)

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Ultrasound Treatment Indications and
Contraindications

• Table 5-8, p. 127 --- Memorize!!!
• Guidelines for the safe use of ultrasound
  equipment, p. 126-127