US 3457924 A
Description (OCR text may contain errors)
y 969 w. D. KENDALL 3,457,924
- v BODY LOAD SENSITIVE ELECTROTHERAPEUTIC EQUIPMENT Filed July 21, 1966 5 iv VEN 7'02.
, mun/w DEN/s KENDALL 51 #426 K W 2000 vac Q v firromvsys.
United States Patent 3,457,924 BODY LOAD SENSITIVE ELECTROTHERAPEUTIC EQUIPMENT William Denis Kendall, Los Angeles, Calif., assignor to Dynapower Systems Corporation of California, Santa Monica, Calif., a corporation of California Filed July 21, 1966, Ser. No. 566,814 Int. Cl. A61n 1/00 US. Cl. 128-404 Claims ABSTRACT OF THE DISCLOSURE The disclosure concerns improvements in transmission of pulsed RF. energy to a patient, and operatively characterized in that substantial power is radiated by a treatment head only when a body or patient load is presented closely proximate a treatment head antenna, the head including a capacitor forming a tank circuit With the antenna and which remains spaced from the body load.
This invention elates generally to electrotherapeutic apparatus, and more specifically concerns improvements in transmission of pulsed R.F. energy to a patient, as for example to produce heating of body tissue.
The invention is particularly directed to the solution of problems arising Where pulsed R.F. energy is transmitted to the patient via a coaxial cable and a radiating antenna at a treatment head. Among such problems are inefficiency of energy transfer to the patient; heating of the cable, indicating undesirable energy loss; lack of proper impedance matching; and relatively slow tissue heating effect, as for example a 2 to minute interval required to produce desired heating of tissue. Another problem is the difiiculty of maintaining the carrier frequency transmitted by the head at a fixed, predetermined value, as for example 27.12 megacycles.
It is a major object of the present invention to provide a solution to the above as well as other problems associated with prior electrotherapeutic apparatus. Basically, the invention embodies the provision of equipment operatively characterized in that substantial power is radiated by a treatment head only when a body or patient load is presented closely proximate the head antenna, the load in effect presenting sufficient capacitance as to couple with the antenna coil to produce a resonating condition under which optimum energy transfer occurs. At the same time, the coaxial cable is not coupled to the antenna in such manner as to produce cable heating, but rather acts primarily as a conductor of RF. voltage, and remains cool.
The above object is realized in accordance with the invention by providing a power radiating head having an antenna in the form of a spiral coil, a condenser electrically connected to form a tank circuit with the coil, the coil having an input tap, and means to supply pulsed high frequency in the megacycle range to the tap, with the tap located with respect to the coil so that substantial power is radiated by the head only when a body load is presented closely proximate the coil. Typically, a coaxial cable supplies the pulsed R.F. energy to the tap, and an impedance matching capacitor is connected at the head in series between the center conductor and the tap, the capacitance of that capacitor being greatly in excess of the capacitance of the cable at the pulsed high frequency; also the tap is typically located with respect to the coil so that the impedance matching capacitor, the coil condenser and body load from a tuned circuit resonant at about 27 megacycles, and which is detuned in the absence of body load presentation to the head.
Other objects of the invention include the provision of Ice an impedance network comprising inductance and capacitance connected in series between a source of pulsed high frequency and ground, the coaxial cable conductor input coupled to the network, as for example to the network inductance; and the network capacitance may include series connected capacitors connected in parallel with the network inductance, the cable center conductor coupled to the network intermediate the network capacitors.
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:
FIG. 1 is an elevation taken in section through a treatment head;
FIG. 2 is a section taken on lines 22 of FIG. 1;
FIG. 3 is a diagram of circuitry at the head; and
FIG. 4 is a diagram of input circuitry.
In the drawings, the head is shown in the form of a generally cylindrical metallic shell 10 having a front opening 11 and a closed rear wall 12 supported by a rod or similar member 13. Received through the front opening 11 is an assembly that includes means in the form of a spiral coil antenna 14 operable to effect radiation of pulsed high frequency energy for treatment of a patient presented to a body load, such treatment for example including deep diathermy effect. A support for the antenna coil turns includes-dielectric arm members 15 and 16 interconnected at 17, the arm terminals being suitably attached at 18 to the shell. The antenna turns are typically retained in grooves 19 formed in the arm members, as shown. The assembly also includes a condener 2t] electrically connected with the coil to form a tank circuit, the large generally parallel plates 21 and 22 of the condenser being respectively connected via leads 23 and 24 with opposite terminals 25 and 26 of the coil. In this regard, the coil terminal 26 and capacitor plate 22 are grounded via connection 32 to the sheath 27 of coaxial cable 28 as is also clear from FIG. 3. Further plates 21 and 22 of the condenser may be insulatively supported by dielectric block 29 connected to the shell 10. An insulative fastener 30 holds the condenser plates at predetermined separation, factory adjusted and set.
Further in accordance with the invention, the antenna coil 14 has an input tap at 31 to which pulsed high frequency energy in the megacycle range is supplied, the tap being located with respect to the coil, so that substantial power is radiated by the head only when a body load is presented closely proximate the front of the coil load 33 is indicated directly frontwardly of the insulative cover 34' for the shell. Means to transmit pulsed high frequency energy in the megacycle range to the coil includes center conductor 34 of cable 28, and an impedance matching capacitor 35 connected at the head in series between the center conductor and tap 31. The capacitance of the capacitor 35 is substantially in excess of the capacitance presented by the cable at the transmitted high frequency, the cable being between 8 and 12 /2 feet long. Accord ingly, the cable remains cool, and very little energy loss is sustained in the cable itself.
Finally, the tap is located with respect to the coil so that the capacitor 35, coil 14, the condenser 20 and body load together form a tuned circuit resonant at about 27.12 megacycles, the circuit being detuned in the absence of load 33. In this regard, the body load is represented as capacitance 33a in FIG. 3, i.e. the additional capacitance required for resonance, with rapid and eflicient radio frequency energy transfer to the body load indicated by rapid heating thereof, as for example in a matter of a few seconds rather than minutes required in previous devices. Other advantages include absence of the cable in the resonant circuitry, better impedance matching with the body load, less loss of energy during its transmission to the body load, and transmission of substantial energy only when load 33 is presented in FIG. 1 position, as indicated by off state of light 60 when load 33 is absent and on state of light 60 when load 33 is present. A wire loop 61 in the shell inductively supplies voltage to light 60. In the drawings, the tap 31 is located about /2 turn from the end 26 of the 4.6 turn antenna coil 14. The coil itself is typically about 10 inches in overall diameter and consists of copper wire. A source of pulsed high frequency energy is indicated at 40, and may take the form of the apparatus described in US. Patent 3,127,895.
The means to transmit pulsed high frequency energy to the tap may also include an impedance matching network of unusual effectiveness in working combination with the head as described, and comprising capacitance and inductance connected in series between a pulse source and ground, the cable center conductor input 34a being electrically connected to the network, as for example the network inductance seen at 45 in FIG. 4. That illustration also indicates the network capacitance to include series connected capacitors 46 and 47 connected in parallel with inductance 45, the center conductor 34 being coupled to the network at a point 48 intermediate the capacitors.
Purely illustrative values for the circuit elements described and illustrated are given below, other workable values also being usable:
Capacitors: Value 35 ,u,u.f 5O 20 ;t,u.f 6 46 ,up.f 50 47 r" 82 49 ,u.f .Ol 51 ....,u.f .01 Coils: 45 microhenries 4.7
1. In electrotherapeutic apparatus, a power radiating head including first means to effect radiation of pulsed high frequency energy for treatment of a patient presenting a body load, said means including a spiral coil and a condenser electrically connected to form a tank circuit, the coil having an input tap, and means to supply pulsed high frequency in the megacycle cange to said tap, the tap located with respect to the coil so that substantial power is radiated by the head only when a body load is presented closely proximate the coil, the head including a shell and the coil and condenser having electrically interconnected terminals electrically grounded with respect to the shell.
2. The apparatus of claim 1, in which said last-named means includes a coaxial cable having a center conductor, and an impedance matching capacitor connected at the head in series between said center conductor and said tap.
3. The apparatus of claim 2, in which said tap is located with respect to the coil so that the impedance matching capacitor, the coil, the condenser and the body load form a tuned circuit resonant at about 27 megacycles, said circuit being detuned in the absence of said body load.
4. The apparatus of claim 2, in which said last named means includes an impedance network comprising other capacitance and inductance connected in series between a source of said pulses and ground, said center conductor input being electrically connected with said network.
5. The apparatus of claim 4, in which said network capacitance includes series connected capacitors connected in parallel with said network inductance, said center conductor being coupled to said network intermediate said network capacitors.
References Cited UNITED STATES PATENTS 2,276,996 3/1942 Milinowski 128422 3,299,892 l/l967 Kendall et al. 128-421 FOREIGN PATENTS 451,310 8/1936 Great Britain.
WILLIAM E. KAMM, Primary Examiner