Transcript The Basis For The Use Of Therapeutic Ultrasound

Therapeutic Ultrasound
Jennifer Doherty-Restrepo, MS, LAT, ATC
Entry-Level ATEP
Therapeutic Modalities
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

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
Longitudinal Waves


Primary waveform for
travel in soft tissue
Molecular displacement
occurs along the
___________________
___________
Transverse Waves


Primary waveform for
travel in ______
Molecular displacement
is _______________ to
direction of wave
propagation
Frequency Of Wave Transmission
Audible sound = _______________
Ultrasound > _______________
 Therapeutic Ultrasound = _______________
(1,000,000 cycles/sec)
 Penetration and absorption are ____________
related

 Lower
frequencies = ______ depth of penetration
 Higher frequencies = superficial ______________
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 _______________
Attenuation
_______ in energy intensity as the ultrasound
wave is transmitted through various tissues
 ________ is due to absorption, dispersion, or
scattering, which result from __________ and
__________

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
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
_______________
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”
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
Ultrasound Generator
Electrical Output
Mechanical Vibration
Acoustic Soundwave
Absorbed In The Tissues
Therapeutic Ultrasound
Generator Control Panel
Timer
 Power meter
 Intensity control

 _______________

Duty cycle switch
 _______________
Selector switch for continuous or pulsed
 Automatic shutoff if transducer overheats

Transducer

AKA:
 _______________,
or
 _______________


Not interchangeable
Piezoelectric crystal
 Quartz
 Synthetic

ceramic crystal
Converts ____________
energy to _____ energy
through mechanical
deformation
Piezoelectric Effect

When an alternating current generated at the same
frequency as the crystal resonance is passed
through the peizoelectric crystal, it will ________
and _______________
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
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
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

Frequency of Therapeutic Ultrasound


Depth of penetration is
__________________
not intensity dependent
1 MHz = deep heat
 _______________

3 MHz = superficial heat
 _______________
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
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
Ultrasound Beam


Point of Maximum
Acoustic Intensity
As acoustic waves
move ________ from
transducer, they
become
indistinguishable and
arrive at a certain
point simultaneously
Ultrasound Beam



Far Field
Waves travel beyond
the point of maximum
acoustic intensity
Energy is more _____
___________ and the
beam becomes more
divergent
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 _______________

point of intensity = 6 W/cm2
 Average output of intensity across transducer =
1 W/cm2
 Maximal
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

Pulsed vs. Continuous Ultrasound

Continuous Ultrasound
 Ultrasound
intensity remains constant over time
 Ultrasound energy produced ________ of the time
Pulsed vs. Continuous Ultrasound

Pulsed
 Ultrasound
intensity is interrupted with no energy
produced during the off time
 Average intensity of output over time is _________
Pulsed Ultrasound and Duty Cycle

Duty Cycle
 Percentage
of time that ultrasound is being generated
(pulse duration) over one pulse period
 Pulse period = mark:space 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
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 (______________)
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
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:
watts = 1.5 W/cm2
cm2
6
4
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
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 ______________________
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
dependent
are temperature dependent, not time
Physiologic Effects of
Ultrasound
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 > _______________
 Whenever there is a thermal effect there
will always be a non-thermal effect

Thermal vs. Non-Thermal Effects

To elicit thermal therapeutic effects, tissue
temperature must be raised to a level of 4045°C for a minimum of ___ minutes
 Baseline

Mild heating: temperature  of _____


metabolism healing and healing
Moderate heating: temperature  of ______


muscle temperature is _________
pain and muscle spasm
Vigorous heating: temperature  of ____

extensibility of collagen and  joint stiffness
Thermal Effects of Ultrasound
Increased collagen extensibility
 ________ blood flow
 ________ pain
 Reduction of muscle spasm
 ________ joint stiffness
 Reduction of _______________

Ultrasound Rate of Heating Per Minute

Intensity W/cm2
1MHz
0.5
1.0
1.5
2.0
.04°C
.2°C
.3°C
.4°C
3MHz
.3°C
.6°C
.9°C
1.4°C
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
Ultrasound Rate of Heating Per Minute

Intensity W/cm2
1MHz
0.5
1.0
1.5
2.0
.04°C
.2°C
.3°C
.4°C
3MHz
.3°C
.6°C
.9°C
1.4°C
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
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
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
Cavitation

Formation of gas-filled
bubbles that expand and
compress due to
ultrasonically induced
pressure changes in
tissue fluids
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
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

Techniques of Application
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
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
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
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
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 _________
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
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
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
Bladder technique



Good for treating
irregular surfaces
Uses a balloon filled
with water
Both sides of the
balloon should be
liberally coated with a
_______________
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 ______
_________

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, databased evidence concerning its efficacy
 Most of the available data-based research is
unequivocal

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)
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)

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)

Bone Healing

Ultrasound ___________ fracture repair


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


(Dyson, 1982, Pilla et al., 1990)
(Ziskin, 1990)
Not effective in detecting _______________
Pain Reduction
Ultrasound treatments are not used
specifically for pain modulation
 Ultrasound may increase the ___________
____________ of free nerve endings



Superficial heating may effect gating of pain
impulses - _______________


(McDiarmid, 1987)
(Williams et al. 1987)
Increased nerve conduction velocity creates a
_______________ effect

(Kitchen, 1990)
Placebo Effects

A number of studies have demonstrated a
placebo effect in patients using ultrasound
 (Lundeberg, 1988, Dyson, 1987, Hashish et al., 1986)
Phonophoresis
Ultrasound energy used to drive topical
application of selected medications into the
tissues
 _______________

 Cortisol
 Salicylates
 Dexamethasone

_______________
 Lidocaine
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)
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 InflammatoryResponse Phase of healing

US and E-Stim = _______________
 Effective
in treating myofascial trigger points when
used in combination with stretching (Girardi, et al. 1984)
Ultrasound Treatment Indications
and Contraindications
Table 5-8, p. 127 --- Memorize!!!
 Guidelines for the safe use of ultrasound
equipment, p. 126-127
