International Journal of Emerging Technology and Advanced Engineering
Website: www.ijetae.com (ISSN 2250-2459, Volume 2, Issue 11, November 2012)
Implementation Of Interferential Therapy (IFT) Using
Microcontroller
Mrs. Nikita. P. Joshi1
1
Lecturer in Electronics, Government Polytechnic Miraj
These two signals produce an interferential current
signal with amplitude modulated frequency of f=f2-f1 as
shown in fig. This is called Beat frequency. The
interference takes place inside the body. Therefore carrier
waves achieve greater depth of penetration, due to their
high frequencies that short circuit the skin capacitance,
and produce interferential current while the resulting beat
frequency signal causes the desired therapy.
The effect of tissue stimulation with these medium
frequency currents (1KHz to100KHz) has yet to be
established. The magnitude of the low frequency
interference current is approximately equivalent to the
sum of the input amplitudes. It is difficult to show
categorically that this is the case in the tissues but it is
reasonable to suggest that the resultant current will be
stronger than either of 2 input currents.
Abstract -- In This paper the design and implementation
of an Interferential therapy unit is discussed. The basic
principle of Interferential Therapy is to utilize the
significant physiological effects of low frequency (<250 Hz)
electrical stimulation of nerves without the associated
painful and somewhat unpleasant side effects sometime
associated with low frequency stimulation. Interferential
therapy uses two medium frequency currents, passed
through the tissues simultaneously, where they are set up so
that their paths cross and they interfere with each other.
This interaction gives rise to an interference current (beat
frequency) which has the characteristics of low frequency
stimulation.
Keywords — IFT, IFC, SWEEP
I. INTRODUCTION
Generally low frequency with sufficient intensity is
used for muscle stimulation. But the main problem
associated with the application of low frequency current
to patients is the very high skin impedance, because
Z=1/2∏ FC, where F is frequency. Using high frequency
current will reduce the impedance and hence reduce the
discomfort that is caused by low frequency currents. At
the same time, Interferential current (IFC) produces low
frequency effects in deeper tissues of the body resulting
in the therapeutic effect of the low frequency current
therapy.
III. FREQUENCY SWEEP
Nerves will accommodate to a constant signal and a
sweep (or gradually changing frequency) is used to
overcome this problem. The principle of using the sweep
is that the machine is set to automatically vary the
effective stimulation frequency using pre set or user set
sweep ranges. There are following sweep patterns as
shown in fig 2
II. WORKING PRINCIPLE
FIG. 1 GENERATION OF AMPLITUDE MODULATED INTERFERENCE
WAVE
To create the interferential current signal, two carrier
signals with different frequencies are used for the
interference. For example f1=4000Hz and f2=4100Hz.
FIG 2 A) RECTANGULAR SWEEP PATTERN, B) TRIANGULAR SWEEP
PATTERN, C) TRAPEZOIDAL SWEEP PATTERN
139
International Journal of Emerging Technology and Advanced Engineering
Website: www.ijetae.com (ISSN 2250-2459, Volume 2, Issue 11, November 2012)
The sweep range employed should be appropriate to
the desired physiological effects. It has been repeatedly
demonstrated that wide sweep ranges are ineffective
whenever they have been tested in clinical environment.
When these two electrodes are applied across affected
painful area then medium frequency waves achieve
greater depth of penetration, while the resulting beat
frequency signal causes the desired therapy.
IV. MICROCONTROLLER BASED IFT
VI. IFT USING FOUR ELECTRODES
In this mode of operation Oscillator of channel1
generates 4KHz or 2KHz frequency signal. The selection
of frequency is also done by microcontroller. Oscillator
of channel2 generates either (4KHz + Beat frequency) or
(2KHz + Beat frequency) depending on frequency
selection. Output of both oscillators are fed to
corresponding buffers and then to respective power
amplifiers. Gain of power amplifier is controlled by
microcontroller. Thus amplified frequency signals 4KHz
or 2KHz & (4KHz + Beat frequency) or (2KHz + Beat
frequency) will appear across channel 1 electrodes &
channel 2 electrodes respectively. When four electrodes
are applied to the body, the optimum interference effect
occurs when they are arranged cross diagonally as shown
in the fig. 4 the currents Maximum nerve excitation
occurs endogenously in the region of the tissue where the
currents from the two circuits cross. Around the
geometric center between the four electrode, the total
current is the sum of from each pair of electrodes.
Interferential Therapy delivers a continuous stimulation
deep into the affected tissue.
FIG. 3 BLOCK DIAGRAM OF MICROCONTROLLER BASED IFT
Block diagram of microcontroller based IFT is as
shown in fig. 3. This IFT is battery operated. Chargeable
battery is connected to microcontroller. The battery
voltage is read by controller, if it is less than 12.5V
charging of battery starts & if the battery voltage
becomes greater than 14V then charging of battery stops.
With the help of 4 X 4 keyboard matrix different modes
of operations of IFT is selected. This IFT is operated in
two modes of operations. 1) IFT using two electrodes
(one channel) 2) IFT using 4 electrodes (two channels).
These two modes are controlled by analog switch. When
it is on first mode is selected & when it is off mode 2 is
selected.
V. IFT USING TWO ELECTRODES
In this mode of operation Oscillator of channel1
generates 4KHz or 2KHz frequency signal. The selection
of frequency is also done by microcontroller. Oscillator
of channel2 generates either (4KHz + Beat frequency) or
(2KHz + Beat frequency) depending on frequency
selection. Beat frequency is also selected by
microcontroller. Outputs of both oscillators are fed to
modulators. Modulator adds these two frequency signals
with slightly out of phase (synchronization). Due to this
modulator gives amplitude modulated wave with
frequency equal to beat frequency. This AMF (amplitude
modulated frequency) signal is amplified by output
power amplifier. The gain of output power amplifier is
also selected by microcontroller with the help of gain
control. Output of power amplifier drives electrodes of
channel 2.
FIG. 4 GENERATION OF INTERFERENCE CURRENT
VII. THERAPEUTIC USES
There are 4 main clinical applications for which IFT
appears to be used.
140
International Journal of Emerging Technology and Advanced Engineering
Website: www.ijetae.com (ISSN 2250-2459, Volume 2, Issue 11, November 2012)
1) Pain relief - Electrical stimulation for pain relief
has widespread clinical use. IFT uses 90-130Hz
frequencies to stimulate the pain gate mechanism
& thereby mask the pain symptoms.
2) Increase local blood flow - IFT causes muscle
contraction which brings about a local metabolic
and thus vascular change.
3) Reduction of Oedema - IFT has been claimed to
be effective as a treatment to promote the
reabsorption of oedema in the tissues.
4) Other clinical applications - IFT is almost used to
treat almost any conditions where inflammation is
a problem. Ex.-sports injuries, arthritic conditions,
bruising and swellings, back pain, osteo arthritis,
muscular pain etc.
REFERENCES
[1 ] Watson T. (2000) The role of electrotherapy in contemporary
physiotherapy practice. Manual Therapy Aug:5(3);132-41
[2 ] Kullervo Hynynen, “Review of Ultrasound Therapy”, IEEE
Ultrasonic Symposium, 1313, 1997
[3 ] Wilkin LD, Merrick MA, Kirby TE, Devor ST. "Influence of
therapeutic ultrasound on skeletal muscle regeneration following
blunt contusion", Int J Sports Med. 2004 Jan; 25(1):73-7
[4 ] Stuart J. Warden, BPhysio (Hons), PhD, Keith G. Avin, MS, Erin
M.Beck, PTA, Marie E. DeWolf, ATC, Molly A. Hagemeier, and
Kristin M. Martin "Low-Intensity Pulsed Ultrasound Accelerates
and a Nonsteroidal Anti-inflammatory Drug Delays Knee
Ligament Healing", The American Journal of Sports Medicine,
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[5 ] Warden, SJ “A new direction for ultrasound therapy in sports
medicine”, Sports Med., 33(2), 95-1, 2003. Duane O. Hall, Sandy,
Utah, “Interferential Electrical Current Therapy Systems and
Methods,” Appl.No: 177,569, Apr. 4, 1988
[6 ] Tammy Crouch, Carpal Tunnel Syndrome & Repetitive Stress
Injuries, Frog. Ltd, 1995, pp.47- 55.
[7 ] http://www.physiomontreal.com/IFC.pdf
[8 ] http://www.morganelectroceramics.com/
[9 ] http://en.wikipedia.org/wiki/File:555_Astable_Diagram.svg
[10 ] http://www.kpsec.freeuk.com/555timer.htm#astable
[11 ] David L. Terrell, Op Amps: Design, Application, and
Troubleshooting, 2nd ed., 1996, pp.209-230
VIII. CONCLUSION
The clinical application of IFT therapy is based on
response threshold and the physiological behavior of
stimulated tissues. Since IFT acts primarily on the
excitable tissues like nerves and muscles, the strongest
effects are likely to be those produced by such
stimulation, i.e. pain relief and muscle contraction. The
other effects like drainage of fluid and reduction in
muscle spasm are secondary consequences of the primary
effects.
REFERENCE BOOKS:
[12 ] Clayton’s Electrotherapy; By Angela Forster & Nigel Palastanga
[13 ] Clinical Electrotherapy; By Roger M.Nelson & Dean P.Currier
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