Ultrasound 10cm2
Ultrasound (US)
Therapeutic ultrasound
– Uses acoustic energy, delivered at high
frequencies for therapeutic purposes
Electrical current creates a mechanical vibration in
a crystalline material housed in a “head” of the unit
Vibration of this material produces acoustic energy
Energy emitted from the head travels through
tissues and is absorbed
– Sound energy used for diagnostic imaging
differs in amplitude and pulse characteristics
Ultrasound (US)
Crystal quality and size: BNR and ERA
Effective radiating area (ERA)—the area that
receives at least 5% of the peak sound energy
Beam nonuniformity ratio (BNR)—ratio between
peak amplitude and the average amplitude of
the ultrasound beam across the ERA
– The lower the BNR, the more uniform the intensity of
the sound wave
– Lower BNR minimizes the risk of “hot spots” and
allows for higher doses to be applied
– Acceptable BNR range is between 2 and 6 (must be
listed on all units)
Ultrasound (US)
Conducting media
Substances used to conduct US
– US gel and gel pads—effective conductors
– Mineral oil—poor
– Lotions—poor
– Water—may attenuate as much as 66% of
sound waves; not very good
Ultrasound (US)
Parameters of treatment with US
Amplitude—clinician controlled
– Sound energy emitted by crystal measured in watts
(W)
– Dose of sound energy delivered is based on amount
of energy being emitted divided by the radiating area
of the crystal, which is measured in square
centimeters
– US dose is measured in W/cm2
Duty cycle
– Ratio of “on” time to “off” time (pulsed)
– No interruption: 100% duty cycle or continuous US
Ultrasound (US)
Duration of treatment
Frequency
– Affects the depth at which greatest amount of
US energy is absorbed
– Typically either 1 MHz (deeper) or 3 MHz
(superficial)
– Most older units have a single fixed frequency
of 1 MHz, but those offering more than one
are now common
Ultrasound (US)
Sound energy absorption in tissues
Tissues with greater protein density have a
higher rate of US absorption
– Tendon, ligament, and muscle tissue
– Superficial bones and nerves absorb the most energy
Tissues with higher water content have a lower
absorption rate (skin and adipose tissue)
US at a higher frequency (3 MHz) is absorbed
more rapidly than at a lower frequency (1 MHz)
Ultrasound (US)
Thermal effects of US
Potential to increase local blood flow
Increases in collagen elasticity
Analgesic and antispasmotic responses
not as great as those following
cryotherapy, superficial heating, and TENS
Ultrasound (US)
Tissue heating and cool-down
Duty cycle
– Continuous US results in therapeutically beneficial amounts of tissue
heating
– Total energy delivered during pulsed US is less at the same intensity
and duration
Dose
– The greater the dose of sound energy, the greater the amount of energy
delivered to the tissues
– With continuous US, higher dose results in greater tissue heating in less
time
Treatment time
– Interaction among frequency, dose, and time required to increase tissue
temperature
– Longer applications needed when lower intensities of US are used
Ultrasound (US)
Treatment area
– When larger areas are treated, the amount of acoustic energy
reaching any single area is decreased
– Best recommendation suggests treatment area of two to three
times the ERA
Sound head movement
– Moving sound head slowly prevents hot spots and helps to
maintain good surface contact
– Rapid, sloppy movement of the sound head with infrequent
surface contact decreases thermal response
Thermal response to US is short-lived
– Superficial tissues cool more rapidly
– Stretching or manual therapies should be performed immediately
for benefits of US to be realized
Interferential
Is used to Reducing pain
Uses 4 electrodes to deliver 2 currents, one
current w/ a constant frequency and the other
current w/ a variable frequency
Frequency of over 4000 Hz = comfortable &
able to pass through the skin surface
Where they cross is called the “beat”
General accepted range is 80 to 150 Hz, w/ low
0 to 10Hz
– Low range is to increase local blood circulation
– High range for pain relief
Premodulated (Bi-Polar) Therapy
Reduces pain and increases R.O.M.
Used for treating small areas where 4
electrodes cannot be placed
Uses one output jack w/ a waveform
identical to interferential current while only
using 2 electrodes
Russian Stimulation
The output of this is a 2,500 Hz sinusoidal
wave.
Russian stimulation currents produce
strong muscle contractions.
Allows the user to choose muscle
contraction/relaxation cycle from a preset
option of 10/10, 10/20, 10/30, 10/40 &
10/50 or user-defined or continuous
Russian Stimulation
Ultrasound 2cm2