Note: Descriptions are shown in the official language in which they were submitted.
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PULSE EL~CTRO-MAGNETIC FIELD THERAPY DEVICE WITH AUTO
BIASED CIRCUIT AND METHOD FOR USE
Backqround and SummarY of the Invention
The present invention pertains to a magnetic-field-
producing therapy device for treating animal tissues with a time-
varying magnetic field. Specifically, the therapy device of the
instant invention generates a substantially only unipolar
electro-magnetic pulse which assists a patient's bodily healing
mechanism, thereby promoting faster healing of broken bones and
enhancement of circulatory deficiencies.
The use of electrical energy to produce modifications
in living tissue is well known. Electro-magnetic devices have
been used to promote healing of broken bones. A. T. Barker, The
Desiqn of a C_inlcal Electro-Maqnet c Bone StimulatorL Clinical
PhYsical Phy~_oloqY Measurement, February, 1981, Volume II, No.
1, Pages 9-16. Additionally, use of pulsed electro-magnetic
fields (PEMF) to promote healing of bone tissue is described in
~.S. Patent No. 4,315,503 to Ryaby, et al. and in U.S. Patent
No. 3,890,953 to Kraus, et al.
Use of electro-magnetic energy to arrest arthritic
pain has been disclosed in U.S. Patent No. 3,902,502 to Liss, et
al.
~ reading of the rather extensive literature in the
field of electro-magnetic treatment teaches that there is little
agreement amongst researchers in the field as to the most
effective pulse wave form, frequency, and voltage level for
treatment of tissue disorders. Without delving into the merits
of one treatment method over the other, the present invention
relates to an electro-magnetic-field-producing therapy device
which generates a su~stantially rectangular, unipolar, electro-
magnetic pulse of a predetermined frequency and amplitude and
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which includes a biasing means for preventing generation of a
transient negative pulse when a positive, unipolar pulse
collapses at the end of a duty cycle. The biasing means also
substantially eliminates high frequency ringing at the beginning
of a treatment pulse. A method of treating animal tissues with
a time-varying, electro-magnetic field and apparatus for
carrying out the method are taught. The method involves
generating pulses in a frequency range of 1-100 hertz at an
amplitude of 1-15 volts.
A basic premise of the teaching is that a negative
pulse or spike which may form upon the collapse of a positive
electro-magnetic field has a detrimental effect on the healing
which is sought to be promoted by the application of the electro-
magnetic pulse. Use of PEMF devices to promote vaso-
constriction has not been successful due to the presence of high-
frequency ringing at the beginning of a device duty cycle.
An object of the invention is to provide a method of
treating animal tissue with a time-varying magnetic field,
wherein the field is generated by a substantially rectangular,
unipolar electro-magnetic pulse which is passed through a
magnetic coil wherein the coil is biased to prevent the
occurrence of a reverse polarity pulse upon the decay of the
generated field.
Another object of the invention is to provide a device
which will generate a magnetic field and which includes
circuitry to prevent generation of a transient reverse polarity
pulse upon the collapse of the generated field.
A further object of the invention is to provide a
device which will be effective to form an electronic ice pack by
acting as a vaso-constrictor.
In the preferred embodiment, a treatment pulse
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generator controls the frequency of magnetic pulses which are
transmitted to a patient undergoing treatment. Circuitry is
provided such that the initial frequency is ten times that of
the ultimate treatment signal frequency, thereby allowing for
substantially instantaneous adjustment of treatment qignal
frequency. This is particularly desirable when the device
output is in very low frequency ranges, i.e. 0.1-20 hertz. A
biasing circuit is provided in the device which induces an
electrical current of the same polarity as the treatment signal
through the treatment coils, thereby absorbing any reverse
polarity spikes which may be generated simultaneously with
collapse of the treatment signal generated field.
These and other objects and advantages of the instant
invention and the method will become more fully apparent as the
description which follows is read in conjunction with the
drawings.
Description of the Drawinqs
Fig. 1 is a block diagram of the magnetic-field-
producing therapy device of the instant invention.
Fig. 2 is a schematic diagram of a biasing circuit
incorporated into the therapy device.
Fig. 3 is an illustration of wave forms produced and
induced by the device without an operational biasing circuit.
Fig. 4 is an illustration of wave forms produced and
induced by the device with a biasing circuit operating.
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Detailed Descri~tion of the Drawinqs
Turning first to Fig. 1, a block diagram of a magnetic-
field-producing therapy devics made according to this invention
is shown generally at 10. Device 10 includes a pulse generator
12. A signal from generator 12 qoes to frequency counter 14
where it is compared with a signal from a time base generator
16. Frequency counter 14 transmits a signal to a frequency
display 18, which is a digital display in the preferred
embodiment.
The frequency of the signal generated by pulse
generator 12 is adjustable, and in the preferred embodiment, is
generated at ten times the desired output frequency. It is
therefore necessary to provide means for dividing the frequency
produced by generator 12 to a usable, treatment frequency. This
is accomplished by a frequency divider 20. The signal exits
divider 20 and enters duty cycle control 22.
Two signals exit the duty cycle control. An update
signal is transmitted to a digital volt meter 24. A treatment
signal, of a desired treatment frequency, and of a known
relation to the frequency of the signal generated by generator
12, is transmitted to an amplifier 26. Amplifier 26 is
connected to a timer 28 which controls the duration of a
treatment. Timer 28 may also be thought of as an off/on switch.
The treatment signal leaving amplifier 26 is
transmitted to digital volt meter 24 and to a coil means, or,
treatment coil, 30.
Digital volt meter 24 transmits a signal to voltage
display 32. Thus frequency display 18 and voltage display 32
provide complete information as to the freguency and voltage
(amplitude) of pulses being transmitted to the treatment coil.
The components 12 to 28 and 32 comprise what is
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referred to herein as pulse signal generating means.
A biasing circuit 34 provides a maintenance signal to
treatment coil 30 at such times as the polarity of the signal in
line 31 reverses from that of the treatment signal transmitted
by amplifier 26.
Turning now to Fig. 2, biasing circuit 34 is shown in
schematic form. As the treatment signal leaves amplifier 26,
the signal is routed through line 31 and circuit 34. A diode 36
allows the treatment signal to enter the circuit when the signal
is at a high level. The signal charges capacitor 38 and the
remainder pa~ses to variable potentiometer 40~ The signal is
then fed into op amp 42, which has a feedback loop 44 associated
therewith. The signal next pass~s through Darlington-configured
transistors 46 and 48, which together act as a series pass
amplifier, providing a buffer between the op amp and treatment
coil 30.
Capacitors 50 and 52 act as noise suppressor~,
preventing the biasing circuit from acting as an oscillator.
In use, pulse generator 12 initiates a treatment pulse
cycle. The frequency of this cycle is adjustable and the
Erequency, divided by a known relation to the originally
generated frequency, is ultimately displayed on display 18. The
frequency of pulses generated by generator 12 is divided by a
factor of 10, in the preferred embodiment, by frequency divider
20. Amplifier 26 may be varied to adjust the voltage which
ultimately reaches the treatment coil and this value is
displayed by voltage display 32. The signal which is produced
by generator 12 is a substantially unipolar-rectangular wave in
the frequency range of 1-100 hertz. Frequency divider 20 causes
the output signal to range from 0.1 hertz to 100 hertz.
Although the device is capable of producing a much higher
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frequency, it has been found that treatments conducted with
pulses in the frequency range of l-iOO hertz are most ~eneficial
to promoting healing of animal tissue defects sought to be
treated. The device may be used as an electronic ice pack for
vaso-constriction with frequency settings of 0.1 to 5 hertz.
As previously stated, the device of the instant
invention is based on the premise that a unipolar electro-
magnetic pulse is the most effective therapeutic wave form. To
this end, the device generates a treatment signal which consists
solely of positive portions of the rectangular signal. This i5
referred to herein as a unipolar pulse. Duty cycle contxol 22
causes the device to have a 50% duty cycle, thereby resulting in
a substantially square, unipolar pulsed treatment signal. Other
duty cycles may of course be used.
The amplifier has the capability of delivering high
voltage at up to 15 amps, however, the output is generally in
the range of 0.1-15 volts, with the most effective voltages
being in the range of 5.75-12.5 volts. Such a voltage range
results in a magnetic flux level of 4-22 gauss at the coil.
Fig 3a represents a 15 hertz signal measured in line
31. As each unipolar pulse reaches the treatment coil, an
electro-magnetic field is produced. As the pulse terminates,
the electro-magnetic field collapses. This normally results in
a negative or reverse polarity spike as is illustrated at 54.
Fig. 3b represents the wave form as induced in a sensing coil by
the magnetic field generated in coil 30 by the pulsed treatment
signal shown in Fig. 3a. Referring still to Fig. 3b, as a
steady state is reached, at 5~, the wave approaches the ground
or reference line. Vpon initiation of a treatment pulse, the
induced pulse initially is formed as a rather large negative
impulse 58 which i5 immediately followed by a positive spi~e 60.
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This ringing oscillates for approximately 150 microseconds as
depicted in Fig. 3c. As the ringing subsides, the induced
voltage drops off as depicted by the curve at 62. When the
treatment signal ceases, the induced voltage instantly drops, as
shown at 64. The induced voltage gradually returns to a near-
steady state, as shown at 66, prior to the next treatment pulse
being generated.
The inclusion of the biasing circuit results in the
signal form in line 31 shown in Fig. 4a. A maintenance signal
of the same polarity as the treatment signal is transmitted to
treatment coil 30 when a reverse polarity signal is present in
line 31, as the result of the collapse of the field about coil
30. Biasing circuit 34 provides a small voltage, on the order
of 0.2 volts to coil 30 when the generator means is in a non-
duty cycle. As the duty cycle ends, the field about coil 30
collapses, resulting in a reverse polarity signal in line 31.
The presence of such a signal in line 31 "triggers" circuit 34
to transmit a signal component of the same polarity as the
treatment signal into line 34, thereby offsetting the reverse
polarity signal present in the line. The maintenance signal
slightly elevates the wave form above the reference line, as
depicted in Fig. 4a at 68, as opposed to negative spike 54
depicted in Fig. 3a.
The wave form depicted in Fig. 4_ which is induced in
a sensing coii by coil 30 when the biasing circuit is in
operation, has spikes, as shown at 70, 72, but does not exhibit
the extreme spikes, such as 58 and 60 depicted in Fig. 3b, as
when the biasing circuit is not operating. Although a high
frequency ring still occur~ at the peak, the ring has a much
smaller amplitude, as depicted in Fig. 4c, than does the ring
generated by a non-biased signal, and more important, has only
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one reverse polarity spike, as shown at 70. The duration of the
ring is proportional to the treatment frequency.
The strength of the maintenance signal is determined
by the biasing circuit, and specifically by the setting on
variable potentiometer 40. Potentiometer 40 is calibrated in
terms of device output, from 0 to 100~. If, for instance,
potentiometer 40 is adjusted to a value of 20% of device output,
a maintenance ~ignal 20~ the strength of the treatment signal
will be fed to coil 30 when the treatment signal terminates and
the maqnetic field collapses. A maintenance signal 20% the
value of the treatment signal has been found to eliminate any
negative value, or negative spike, generated by the collapse of
magnetic field about treatment and coil 30.
A specific use of the device and method of the
invention is exemplified by a treatment which may be applied to
an animal limb which has, for instance, suffered a bruise. The
device may be used to form an electronic ice pack. As
previously mentioned, known PEMF devices have not been abla to
promote vaso-constriction due to high frequency wave forms which
occur during the ringing at the beginning of the treatment
pulse. A specific coil, formed of 329 turns of 22 gauge wire,
may be applied to a treatment site and a voltage of 12.5 volts
applied. With a frequency setting of 3 hertz, the coil will
produce 22 gauss at the treatment site. This technique has been
found to produce sufficient vaso constriction to reduce the
severity of bruising. The same coil and voltage settings, when
used with a fre~uency of 15 hertz would be effective to treat
soft collagen tissue damage. Various combinations of wire size,
turns and voltages may be utilized, thereby producing magnetic
flux of 0-60 gauss at coil means 30.
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While a preferred embodiment of the invention has been
described, it is appreciate of the variations and modifications
may be made without departing from the spirit of the invention.
