"INDUCTORS FOR HIGH- FREQUENCY ELECTROMAGNETIC . THERAPY, APPARATUS" . , ■ • ^" . ,

This invention relates to high frequency electromagnetic therapy apparatus and particularly to inductors for use witSj such apparatus.

For over forty years, high radio frequency electro- magnetic radiation has been in regular use in the therapeutic treatment of a number of medical conditions. Many pathological processes have been successfully treated, by the direct application to the area under consideration^ of an induced electromagnetic field in the VHF band. The _Q Diapulse Corporation (New York U.S.A.) produces a pulsed VHF electromagnetic field generator suitable for such medical use.

^{"■ "} Present" equipmen is* relatively hig powered and is consequently large. The Diapulse Corporation equipment, 5 for example, can produce a pulsed peak power of 900 watts and an average power output of 1.5 to 38 watts. The inductor which is placed adjacent the area to be treated is approximately the size of a domestic kettle and consequently the patient is somewhat restricted in move- 0 ment during treating sessions.

I have recently discovered that the use of such large amounts of power is in fact unnecessary for the treatment of some conditions, and I have proposed a smaller, portable, high frequency electromagnetic energy therapy 5 apparatus which employs a relatively small treatment inductor. This may be placed in position to leave the patient relatively mobile. Since the patient maintains some mobility and can continue with normal activities during ^• treatment, beneficially longer therapeutic treatment _Q periods are possible.

The treatment inductor I have proposed for use with a high frequency electromagnetic therapy apparatus includes one or more induction elements for connection to said apparatus whereby to enable a high frequency electromagnetic field to be induced, wherein the induction elements are flexible

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and the inductor is embodied in a flexible material where it may be conformed to lie against an area of the body to treated.

By providing the inductor as a flexible body, it may be conveniently attached to the patient by means of surgical tape and will lie naturally against the area to be treated. Normally the inductor will be generally pla but for treatment of acutely curved areas ofthe body, it be more convenient to form the inductor as a complementar curved surface.

The inductor may be part of a tuned circuit of the high frequency electromagnetic therapy apparatus, in whic case the inductor elements will be wound, generally in a circle. The number of turns provided, and any tapping points, will need to be exactly determined to provide the appropriate resonating frequency. The incorporation of t inductor in the tuned circuit can be avoided by including a crystal oscillator in the pulse generator. This arrangement may be preferred since it provides more flexibility to the design of the inductor.

I have now devised two improvements to such flexible induction elements: these improvements may be employed independently of one another but preferably they are employed together. In a first aspect of this invention a treatment inductor such as I have proposed is provided by-forming the inductor elements as conductive areas on a flexible printed circuit board.

The particular configuration for the inductor elemen desired is thus obtained by selective etching of the flexible printed circuit board.

To form the treatment inductors, the i ductor elemen can be etched in the pattern required in the flexible printed circuit board, and the latter then provided with a flexible covering, for example, of silicone rubber.

Various patterns may be provided for different areas of t body, and if a generally-planar inductor is required then

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-3- . product will generally be a sheet-like body of flexible material having the inductor elements therein and having connectOr' leads- extending from -one- edge,. for-.connection to the high frequency electromagnetic radiation generator. 5 The latter is generally a miniaturised VHF pulse generator. The power generated by such apparatus (functioning from small batteries) is in the milliwatt .region.

In a second aspect of this invention a treatment inductor such as described is provided by additionally 10 incorporating a miniature pulse generator (for example an integrated circuit VHF ^" tuned circuit) in or on the inductor _t Preferably the pulse generator is incorporated at the centre of the treatment. inductor with the induction elements spiralling therεaround. 15 By allowing the pulse generator to become an integral part of the treatment inductor, saving may be made in the power required to drive such a unit. The pulse generator is also released from the necessity of being at a fixed distance from the inductor elements. 20 The pulse generator may include a crystal oscillator although this reduces the flexibility of the treatment inductor somewhat.

It will be .appreciated that the two aspects of the invention as described can be conveniently combined. - the 25 flexible printed circuit board being etched to provide the conductive induction elements and being provided with means to take, for instance at the centre, a miniature tuned radio frequency pulse generator.

Preferred features of the invention will now be 30 described with reference to the accompanying drawings, given by way of example, in which:-

Figure 1 is a schematic plan view in cross section of a treatment inductor in accordance with the second aspect of the invention; 35 Figure 2 is a lateral projection of such a treatment inductor, and

Figure 3 is a schematic plan view in cross section of

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a treatment inductor incorporating both, aspects of the invention described.

Referring to Figures 1 and 2, the treatment inductor comprises a spirally-wound, sheathed multifilament electrically-conductive wire 2 having a centre-tapping 4. The wire is embedded in silicone rubber 8 and the whole inductor is of generally-planar appearance. In previous treatment inductors I have proposed, the centre- tapping and both ends of the wire 2 have led to a three pin connector, for connection to a pulse generator remote from the inductor. In accordance with the second aspect of this invention, the connector is omitted, and a miniature pulse generator 20 mounted at the centre of the inductor. The only external connection required, 22, is to a power supply such as a 12 volt battery. In a modification of this aspect of the invention (not illustrated) the batter may also be of miniature form and mounted on the inductor.

The advantage of this aspect of the invention is that it provides the patient with far greater freedom whilst under treatment. If both battery and pulse generator are mounted on the inductor, the latter need only be taped to the area of the body under treatment and the patient allowed to move freely around without external connections thereto. If just the pulse generator is mounted on the inductor then the battery may be carried in a pocket of the patients ¹ clothing or held in a small bag or satchel.

The pulse generator employed in the inductor shown in Figures 1 and 2 may be of standard construction, for example a self-oscillating VHF pulse generator providing pulses in the milliwatt range. A typical pulse generator (such as shown in Figure 3 of my U.K. Patent Specification 7930077) may be based upon a timing unit Type 555 (RadioSpares, London) feeding a power amplifier. Such a circuit can provide output pulses 100 jusec in width at intervals of 1 msec.

Referring to Figure 3, the treatment inductor comprises a flexible printed circuit board 24 with the

-5- . inductor elements 26 formed, as conductive areas thereon. Flexible printed circuit boards are commercially available and the inductor elements 26 ^" are- formed in-t e-usual manner as areas of copper remaining after selective etching of the board. Connection points 28 are provided to which a miniature VHF pulse generator (not shown) and the over- connections to the centre and outer tappings of the inductor elements are connected. The printed circuit board is finally coated with a flexible non-electrically-conductive biologically inert material such as silicone rubber.

Although copper-clad flexible printed circuit boards (as are commercially-available). are convenient starting materials for producing these treatment inductors, the copper (forming the inductor elements) can break under excessive bending in use. For extended treatment periods the use of more flexible electrically-conductive metals may thus be desirable.