Effective Ultrasound Treatments
Jennifer A. Stone, MS, ATC, Column Editor
u
ltrasound is commonly
prescribed to treat athletic injuries. While it also has other uses,
it is generally used because it can
heat tissues directly beneath the
skin. To ensure effective heating
of the tissues, certain parameters
must be considered. Newer research provides more information
to help the athletic therapist select
proper coupling agents, sound
head size, treatment area size,
length of treatment, and ultrasound intensity and frequency.
Coupling Agents: Ultrasound
waves cannot travel through air, so
a medium conducts them from the
sound head to the patient. Substances such as water-based gels,
mineral oil, and water are commonly used. Gels and mineral oil
place the sound head in direct
contact with the patient. Water
treatments are indirect and generally have a 1-cm space between
the patient and the sound head.
Temperature of the coupling
agent can vary from room temperature to body temperature.
Tissue temperature increases
with either gel or water as the coupling agent. Draper et al. (JOSPT,
1993, vol. 17, pp. 247-251) and
Forrest and Rosen (J. Sport Rehab.,
1992, vol. I , pp. 284-289) concluded that ultrasound treatments
using gel in direct contact with the
patient produced more heat than
did ultrasound administered indirectly in water. In these studies
both techniques increased tissue
temperature, but only with gel was
the increase clinically and statistically significant.
Position and Movement of Sound
Head: The sound head must always
be in full contact with the patient
when using gel, and it must be
perpendicular and approximately
1 cm from the patient when under water. Any angulation of the
sound head reduces contact area
and decreases its effective radiating surface.
Optimal speed of movement
of the sound head is 2 to 4 cm per
second. It may be moved either
circularly or linearly. Slower motion increases the risk of thermal
injury because it tends to concentrate the sound waves. Faster motion does not permit optimal absorption of sound waves by the
tissue being treated.
Size of Sound Head and Treatment Area: Most manufacturers
now make equipment with various
size sound heads. Size refers to the
surface area of the crystal, usually
10,5, or 1cm2.Proper sound head
selection takes into account both
the contour and size of the area
being treated. For optimum temperature increase, the treatment
area should be no larger than
twice the size of the sound head.
Trying to cover a larger area reduces the effectiveness of the treatment because the tissue dissipates
any heat generated by the sound
waves prior to another pass of the
sound head. If a larger area must
be treated, divide it into smaller
sections and treat each individually.
Crystal Frequency: Until recently, U.S. ultrasound equipment
was available only in 1 MHz (1
million cycles per second) frequency. But new equipment has
sound heads of several frequencies, including 3 MHz (3 million
cycles per second). The machine
may have several sound heads,
each with different frequencies, or
the frequency may be varied electronically within the machine.
Crystal frequency determines the
depth of penetration. Higher frequency ultrasound is not absorbed
as deeply as lower frequency ultrasound, thus 3 MHz ultrasound
may penetrate 5 cm below the skin
while 1 MHz can penetrate up to
10 cm below the skin.
Prior to the availability of 3
MHz equipment, athletic therapists treated superficial lesions
using 1 MHz ultrasound at reduced intensity. Since 1 MHz ultrasound is not absorbed by superficial tissues, this treatment
protocol did not heat the appropriate tissues and failed to provide
the desired clinical response.
Treatment Time: Traditional
ultrasound protocols recommended a treatment time of 5
min. However, studies by Draper
et al. (JOSPT, 1993,vol. 17, pp. 247251; 1995,vol. 21, pp. 153-157;vol.
22, pp. 142-150)and by Rimington
et al. (J. Athl. Train., 1994, vol. 29,
O 1996 Human Kinetics
40
Athletic Therapy Today
March 1996
pp. 325-32'7) indicate that with
both 1and 3 MHz frequencies, tissue temperature is still rising at the
end of a 10-min treatment. This
suggests that treatment time
should be longer than the traditional 5 minutes for optimal tissue
temperature increase.
Ultrasound Intensity: Ultrasound intensity is usually reported
in watts per cm2. Intensity determines the rate and amount of tissue temperature rise. Higher intensities produce faster temperature
increases and higher tissue temperature for any treatment time.
Athletic therapists often debate
how to determine proper ultrasound intensity. Some maintain
there should be no sensation of
warmth, and others say warmth is
desirable. When choosing intensity, the athletic therapist should
decide how aggressively he or she
wants to heat the tissue, selecting
lower intensities for mild heating
and higher intensities for vigorous
heating.
Conclusion
A better way to train
For maximum ultrasound efficacy,
the following are suggested:
Use gel as the coupling agent.
Keep the sound head in constant, complete contact with
the area being treated.
Move the sound head at 4 cm
per second linearly or circularly.
Select an appropriate size
sound head and treatment
area; the treatment area
should be no larger than twice
the size of the sound head.
Select the proper sound head
frequency, 3 MHz for superficial structures (0 to 5 cm below the skin) and 1 MHz for
deeper structures ( 5 to 10 cm
below the skin).
Treatment time should be no
less than 8 to 10 min for optimal tissue temperature increase.
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1996 Paper
200 pp Item PCHU0643
ISBN 0-87322-643-7
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From minor ankle sprains to serious head injuries,
Sideline Help has the information you need to
respond correctly to all 18 common sports injuries.
For each injury, an easy-to-follow flowchart guides
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@"
uman Kinetics
The Premier Publisher for
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i%e Informatzon Leader in Physical Actzuity
March 1996
Athletic Therapy Today
41