US3543762A - Automatic control of electrotherapeutic apparatus - Google Patents

Description

Inventor William Denis Kendall Los Angeles, California App]. No. 705,647 Filed Feb. 15, 1968 Patented Dec. 1, 1970 Assignee Dynapower Systems Corporation of California Santa Monica, California a corporation of California AUTOMATIC CONTROL OF ELECTROTHERAPEUTIC APPARATUS [56] References Cited UNITED STATES PATENTS 2,551,757 5/1951 Mittelmann 128/422UX 2,752,496 6/1956 Martens 128/422X 3,299,892 1/1967 Kendall et al 128/421 Primary ExaminerWi11iam E. Kamm Attorney-White and Haefliger ABSTRACT: The disclosure concerns electrotherapeutic apparatus employing a power-radiating head useful in diather- 6claims6nnwhg my, and wherein patient movement-induced detuning of a U.S. Cl 128/422, 'tuned circuit at the head is automatically compensated by a 323/65 servoloop including two filters having pass bands above and Int. Cl......; A6ln U40 below the frequency of the therapeutic signal as servomotor Field of Search 1281413: connected to the filters and a variable impedance element in 422, 405, 421; 323/22, 65 the signal circuit adjusted by the motor.

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BACKGROUND OF THE INVENTION ing head, and input means to supply high frequency pulses over a cable to the head for transmission to a patient as in diathermy. The head typically incorporates inductively coupled primary and secondary coils and a condenser electrically connected with the secondary coil to form a tank circuit tuned to a predetermined high frequency in the megacycle range. As an example, that frequency may be 27.12 megacycles, or some other fixed value. It is found that the circuit at the head must be tuned to the input for enabling efficient transfer of energy to the head and to the patient; however, it is further found that movements of the patient tend to detune the circuit at the head due to the capacitive effect of the patient load, with resultant variable and reduced treatment energy transfer to the patient.

SUMMARY OF THE INVENTION It is a major object of the invention to provide a solution to the above problems, through a simple, highly efiicient and unusually effective control arrangement.

Basically, the invention combines with the input means described above a network and transmission line or cable coupled between the input means and the primary coil at the head, the network having a variable impedance element that is controllable to alter energy transmission from the tuned circuit at the head to the patient; and means including a servoloop responsive to patient induced detuning of that circuit to vary the impedance of the element in a direction tending to resist decrease in energy transmission to the patient. As a result, no manual controls are needed for adjusting any impedance element at the head, whereby the construction of the head may remain quite simple. At the same time, there is automatic compensation for movements of the patient relative to the head, a factor that is quite important to maximum energy transfer to the patient for effective treatment.

Additional objects and advantages comprise the inclusion of an oscillator coupled to the input means in such manner that the pulses of high frequency content incorporate a predetermined high carrier frequency J1, and upper and lower side bands f and f respectively, and detector means coupled to the tank circuit to detect differential transmission of f, and f at the head; the provision of a side band responsive servoloop coupled between the tank circuit and the variable impedance element, and the provision of a detector or demodulator in the loop and in the form of parallel channels having filters to pass the signal frequencies f and f in the respective channels, f and f being sufficiently close to f that as the patient moves relative to the head, tank circuit detuning will alter relative amplitudes at the filters of the f and f signals, and a differential amplifier coupled to the filter outputs will drive the actuator to adjust the impedance element in a direction to reduce such detuning.

These and other objects and advantages of the invention, as well as the details of illustrative embodiments, will be more fully understood from the following detailed description of the drawings, in which:

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram of a system incorporating the invention;

FIG. 2 shows the wave form transmitted to the power head;

FIG. 3 is an external elevation showing the console, control panel and the arm supported head;

FIG. 4 is a section taken through the control panel and console;

FIG. 5 is a section taken through the power-radiating head; and

FIG. 6 is a diagram showing a circuit that may be used in FIG. 1 system.

DESCRIPTION OF PREFERRED EMBODIMENTS In the drawings, a power-radiating head is indicated generally at 10, and it includes means operable to effect transmission of pulsed high frequency radiation for treatment of a patients anatomy ll placeddirectly in front of the head. Such a means includes inductively coupled primary and secondary coils l2 and 13, the secondary coil typically having three or four turns and the primary coil a single turn, and acondenser 14 electrically connected with the secondary coil to form a tank circuit. The coils and condenser are shown as located within a drum-shapedmetallic head shell 15 having aninsulative cover plate 16, and the condenser has an insulative mount at 17.

Indicated at 18 in FIG. 1 is an input means to supply pulsed high frequency energy. As an illustration of this, reference is made to FIG. 2 showing the sequence oflike pulses 21, each of which is made up of a high frequency signal burst having aselected amplitude 22, and havingintervals 23 therebetween, these having predetermined relationship. Typically, the signal frequency will be 27.12 megacycles, or some other fixed value, and theinterval 23 will be variable, as for example in stepwise relation. Also the amplitude equal to one-half thedimension 22 will be variable in stepwise relation. Thetime interval 23 may typically be varied so as to provide between about and 5,200 pulses per second in order to increase or decrease the intensity of treatment given to the patient. Apparatus described in U.S. Pat. No. 3,127,895 is usable to provide the waveform seen in FIG. 2.

A network is coupled to the output of the input means, one such network being indicated generally at 25 in FIG. 1 and comprising an unsymmetrical pi-network or low passfilter having capacitors 26 and 27 and aninductance 28 connected as shown. There is also acoaxial cable 29 having asheath 30 and acenter conductor 31, the latter being connected to one terminal of theprimary coil 12. The opposite terminal of thecoil 12 is grounded as by connected to themetallic shell 15. In this regard, no controls are needed at the head for adjusting any electrical impedance elements contained within theshell 15.

Capacitor 27 of thenetwork 25 is located remotely fromhead 10 and atconsole 42. The latter carries an articulatedarm 43 supplied with adjustable joints and swivels to permit universal movement of thehead 10. As will be seen,capacitor 27 is controllable to adjustably match the output impedance that is characteristic of the input means 18 to the input impedance that is characteristic of thecoaxial cable 29 when a patient is undergoing treatment, thereby to optimize energy output of thehead 10 for transmission to the patient. In this regard, the input impedance characteristic of the coaxial cable I is that which is seen by thenetwork 25 looking into" the cable, keeping in mind that the cable,head elements 12, 13 and 14 and the patient 1 1 present a load having an impedance that is seen by thenetwork 25 looking into the cable. The impedance of the load varies somewhat with the patients anatomy presented to the head.

In accordance with the invention, there is provided means including a servoloop responsive to patient induced detuning of the circuit at the head to vary the impedance of an element remote from the head, such ascapacitor 27 at the chassis, in a direction tending to resist decrease in energy transmission to the patient. Accordingly, the circuit is automatically adjusted so as to enable optimum energy transfer, for therapeutic benefit, and thecapacitor 14 at the head need not be adjusted.

In that form of the invention illustrated in FIG. 1, the input means 18 is shown in include an oscillator 50, crystal controlled at 51, to supply a submultiple of the 27.12 megacycle carrier at 52 to buffer amplifier andmodulator 53. Pulse control circuitry 54 is coupled to the amplifier at 55 so as to result in production of thepulses 21 in FIG. 2. Theoutput 56 of anotheroscillator 57 is introduced to the amplifier and modulater 53 in such manner that thecontent ofpulses 21 includes in addition to the predetermined high frequencyf (as for example 27.12 megacycles) upper and lower side bandsf and f respectively, and which are sufficiently close to f that theimpedance 27 will be varied in the manner described and to be described. As an example, theoscillator 57 produces a 100 kc, output at 56, so that the pulse modulated output 59 of theamplifier 53 may be considered to include side bands at 27.02 and 27.22 megacycles, at opposite sides of the 27.12 megacycle carrier, as well as the 27.12 megacycle carrier.

One .way in which theoutput 56 ofoscillator 57 may be injected is shown in FIG. 6. As there illustrated, theoutput 56 is injected at thegrid 60 oftube 61, the switching pulse also being injected at the grid via theinput point 55, as described in U.S. Pat. No. 3,299,892.Power amplifier 62 of FIG. 1 herein corresponds to thepower amplifier 17 in that patent, and the input means 18 herein corresponds generally to the input circuitry of that patent.

Further in accordance with the invention, the above mentioned servoloop may take the form as generally indicated at 70 in FIG. 1, with inductive coupling at 71 with thetank circuit coil 13, and with mechanical coupling at 72 with the rotor of the variable capacitor, as also seen in FIG. 4. The loop as illustrated also includes an actuator, such as a reversibleelectric motor 73, the motor armature rotating thecoupling 72.

Finally, the loop 70 includes what may be generally referred to as a demodulator coupled between the tank circuit at the head and the motor oractuator 73. The demodulator may includeparallel channels 74 and 75 connected at 78 to the inductive coupling 71, and having filters, as for exampleband pass filters 76 and 77, to pass only the signal frequencies f, and f in the respective channels. As the patient moves relative to the applicator head, tank circuit detuning will alter the relative amplitude of f and f signals, resulting in different signal amplitudes at the filter outputs at 80 and 81. Adifferential amplifier 79 receiving input from the filters at 80 and 81 controls the energization of themotor 73 viaconnections 82 and 83 in such manner that in the event the resonant frequency of the tank circuit moves toward the 27.02 megacycle band, more of that signal will be passed via the coupling 71 andfilter 76 to theamplifier 79, and current applied to the motor will cause the motor to adjust thecapacitor 27 until the inputs to the motor atconnections 82 and 83 are more nearly equalized. A similar effect occurs should the patient move to cause shifting of the resonant frequency of the tank circuit toward 27.22 megacycles.

As a result, the compensation for patient movement results in maintaining proper tuning and the desired maximum or near maximum transfer of energy to the patient at all times. Also, the construction of the movable head is maintained as simple as possible.

Iclaim:

1. In electrotherapeutic apparatus including a power-radiating head having first means operable to effect transmission of pulsed high frequency radiation for treatment of a patient, said means including inductively coupled primary and secondary coils and a fixed condenser electrically connected with the secondary coil to form a tank circuit tuned to a predetermined high frequency in the megacycle range, the combination comprising:

input means to supply pulses of said frequency;

a pi network and transmission line coupled between the output of said input means and said primary coil, said network having a variable capacitance element that is controllable to alter energy transmission from said tuned circuit to a patient, said element connected in shunt with said transmission line at the input side of said primary coil; and

means including a servoloop incorporating a detector couenergy transmission to the patient. 2. The combination of claim 1 wherein said servoloop is coupled between said tank circuit and said element.

3. The combination ofclaim 2 wherein said loop includes an actuator coupled with said element, and a demodulator coupled between said tank circuit and said actuator.

4. In electrotherapeutic apparatus including a power-radiating head having first means operable to effect transmission of pulsed high frequency radiation for treatment of a patient, said means including inductively-coupled primary and secondary coils and a condenser electrically connected with the secondary coil to form a tank circuit tuned to a predetermined high frequency in the magacycle range, the combination comprising? input means to supply pulses of said frequency;

a network and transmission line coupled between the output of said input means and said primary coil,said network having a variable impedance element that is controllable to alter energy transmission from said tuned circuit to a patient; and

means including a servoloop responsive to patient induced detuning of said circuit to vary the impedance of said element in a direction tending to resist decrease in energy transmission to the patient, said servoloop being coupled between said tank circuit and said element, said loop including an actuator coupled with said element and a demodulator coupled between said tank circuit and said actuator, said demodulator including parallel channels having filters to pass input means produced signal frequencies f and f, in the respective channels, f and f being respectively higher and lower than said predetermined high frequency but sufficiently close thereto that as the patient moves relative to said head tank current detuning will alter relative transmission by saidfilters of said f, and f, signals, said demodulator also including a differential amplifier coupled to the outputs of said filters.

5. The combination ofclaim 4 wherein said actuator comprises a reversible electric motor connected to differential amplifier outputs.

6. In electrotherapeutic apparatus including a power radiating head having first means operable to effect transmission of having a variable impedance element that is controllable to alter energy transmission from said tuned circuit to a patient; and

means including a servoloop responsive to patient-induced detuning of said circuit to vary the impedance of said element in a direction tending to resist decrease in energy transmission to the patient, said input means including oscillator means operable in said input means in such manner that the high frequency pulses incorporate a predetermined high frequency f and upper and lower side bands f and f respectively, the loop including a detector coupled to said tank circuit to detect differential transmission of f and f at the head.

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