Title of Invention

MAGNETIC FIELD APPLICATOR FOR HEATING MAGNETIC OR MAGNETIZABLE SUBSTANCES OR SOLIDS IN BIOLOGICAL TISSUE

Abstract Magnetic field applicator to heat magnetic or magnetizable substances or solids in biological tissue, with a magnetic yoke with two pole shoes facing each other on the magnetic yoke and separated by a gap in the exposure volume and with two magnetic coils for the production of a magnetic alternating field, each of which is assigned to a pole shoe, wherein the magnetic yoke (2:25) and the pole shoes (7, 8) consist of ferrite building blocks (16, 22 ) mounted together and in that the magnetic coils (9, 10) are disk coils with at least one winding extending helicoidally, each assigned to a pole shoe, and in that the respective pole shoe ends comprise a surrounding magnetic coil/pole shoe gap (a) between them.
Full Text


FORM 2
THE PATENTS ACT, 1970 (39 Of 1970)
COMPLETE SPECIFICATION (See Section 10, rule 13)
MAGNETIC FIELD APPLICATOR FOR HEATING MAGNETIC OR MAGNETIZABLE SUBSTANCES OR SOLIDS IN BIOLOGICAL TISSUE

MFH HYPERTHERMIESYSTEME GMBH of WIESENWEG 10, D-12247 BERLIN, GERMANY, GERMAN Company
The following specification particularly describes the nature of the invention and the manner in which it is to be performed : -

The invention relates to a magnetic field applicator to heat magnetic or magnetozable substances or solids in biological tissue
Cancer diseases are treated in a generally known manner through surgical removal, chemotherapy, radiation therapy or a combination of these methods. Each of these methods is subject to certain limitations: Especially at advanced stages, following metastasis, when the tumor is located close to critical body areas or in case of diffused tumor growth with uncertain localization, surgical removal of the tumor is not possible or only offers minimal chances for a cure. For this reason surgical intervention is generally combined with radiation therapy and chemotherapy. The former can only be as precise as the localization of the tumor by means of image-producing processes and with utmost avoidance or care of healthy tissue. Chemotherapeutic means on the other hand act systemically, i.e. on the entire body. In this case bone marrow toxicity or lack of specificity of the therapy is limiting. Undesirable side effects are therefore unavoidable with all of these therapy methods at the present state of the art and as a rule also cause damage to healthy tissue.
Hyperthermia as another modality has gained in significance over the last few years, consisting in heating the tumor tissue to temperatures above 41 -C so that the success of treatment, i.e. local control and to some extent even survival can be improved in combination with surgery, radiation therapy and chemotherapy. In the temperature range between 41 and 46 C and with the assistance of the body, a controlled and rather slow reduction of the tumor tissue takes place. This process is called hyperthermia, while acute destruction of cells takes place at higher temperatures starting at 47 -C, depending on temperature in form of necrosis, coagulation or carbonization, and the process is then called thermo-ablation. Hyperthermia systems according to the state of the art are suitable only for the above-mentioned hyperthermia or only for thermo-ablation.
One general problem with hypothermia is that no precisely localizable and most of all homogenous heating of target region of the body is as a rule possible according to the state of the art. Under certain physiological conditions (e.g. oxygen deprivation, low pH) in the tumor cancerous cells are sensitive to hyperthermia, but this only applies to few




instances. Hyperthermia in itself is not any more effective on tumor cells than on normal tissue. For this reason the limitation of heating to the area indicated by medicine (and which need not necessarily be confined to the tumor) is especially important, and not realized according to the state of the art.
According to the state of the art, systems dominated by electrical fields are used which radiate the electromagnetic waves as a rule in the megahertz range from antennae or other antenna-shaped objects or arrays of antennae, which are used for regional or local hypothermia. For this either the electrical field of individual electrical-field applicators is used for the so-called interstitial hyperthermia, or the interference of antenna arrays is used for the deep hyperthermia. It is a difficulty common to all of these electrical-field-dominated systems that the power consumption can only be achieved by means of expensive controls of the electrical field and that the heating depends on the electrical conductivity of the applicable target tissue, which is by nature very heterogeneous, so that an uneven heating of the electrical field results, even with homogenous radiation. Especially at the transition points of body regions with very different electrical conductivity, excessive power, or so-called "hot spots" occur for that reason, and these may result in pain and burns inflicted on the patient. The consequence is a reduction of the total emitted power usually demanded by the patient, so that as a result the temperature required to damage the tumor tissue irreversibly (41 - 42 C) is not reached in the target region, so that the therapy is not successful. Furthermore, due to the interference of dipole arrays, only the production of a second electrical field maximum is possible in areas further inside the body. For physical reasons, the greatest power consumption always takes place at the surface of the body, i.e. at the maximum radius. Added to this is the fact that the blood flow through the tumor as well as the normal tissue often changes under hyperthermia, and that this change cannot be compensated for by means of systems dominated by electrical fields from the outside because of the rather low control possibilities of the field.
Other processes according to the state of the an are ultrasound, preferably for thermo-ablation, and interstitial microwave applicators. The latter possess low penetration depth because of the frequency and can therefore only be used in form of interstitial antennae. In addition, infrared for whole-body hyperthermia is used, as well as extra-corporeal systems to heat body fluids.
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Furthermore, a hyperthermia process for the therapy of prostate cancer is known (US patent 5.197.940) in which Thermo seeds" are implanted In the area of the tumor, consisting of magnetic, in particular ferromagnetic or magnetically material or containing such material. These thermo seeds are typically several centimeters long, with a diameter in the millimeter range. It is obviously necessary to implant such thermo seeds surgically at great cost. These thermo seeds are subjected for treatment to an alternating magnetic field produced outside a patient, whereby heat in the thermo seeds is produced by known hysteretic effects in form of hyperthermia.
These seeds are heated according to the "hot source" principle, i.e. that while the seeds are heated, the temperatures in the surroundings of the seed drop exponentially, so that the distance between the seeds may not be more than I cm in clinical application. In case of greater or uneven distances thermal under-dosing occurs which can also prevent the success of the therapy. Especially with larger tumors a very narrow implantation of the seed becomes necessary, so that the method becomes surgically expensive and stressful to the patient. Aside from the small distance, the seeds must be oriented parallel to the magnetic alternating field for optimal power consumption. The Curie temperature in so-called self-regulating thermo seeds prevents overheating in that the ferrite passes into a non- magnetically state when the Curie temperature has been reached and no further power consumption takes place.
A magnetic coil of an oscillatory circuit is used here as the magnetic field applicator for the magnetic alternating field, and a patient's body region with the implanted thermo seeds can be placed in the axis of this oscillatory circuit. In practice air coils are used in the central area of which a patient is sitting on a non-magnetically supporting plate during treatment.
In hyper thermal with thermo seeds the high cost of surgery and severe invasion of the method, the risk of an imprecise orientation or a change in position of the seeds and the ensuing risk of thermal under-dosing as well as a limitation of the method to tumors of smaller size are disadvantages.
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In another known hyperthermia process (WO 97/43005) for tumor therapy, magnetizable microcapsules are proposed which reach the area of the tumor through the blood stream, In this way surgical implantation of magnetically elements should be avoided among other things, since with implantations, the danger exists in addition to the stress to which a patient is subjected, that malignant tumor cells may be dispersed into healthy tissue when a cut is made into the tumor. A linear magnetic alternating field is used with a frequency in the range of 10 kHz to 500 kHz. The microcapsules are to be used in conjunction with a highly magnetically material, so that the force of the magnetic alternating field which is required for the field can be manageable with respect to the instrumentation structure of the required cooling system as well as to the electrical energy supply. A practical instrumentation structure is how'-ever not indicated.
In a very much similar, known Hyperthermia process (EP 0913 167 A2) rotating magnetic fields with a frequency in the range greater than 10 kHz are used as fields. To produce the rotating magnetic alternating field used here, a magnetic field applicator of this type is indicated only sketchily and schematically. The magnetic field applicator comprises a magnetic yoke with two pairs of pole shoes across from each other and separated each other by a gap in the exposure volume and two pairs of magnetic coils assigned to these pole shoes. In reality a rectangular magnetic yoke is shown whereby a pole shoe is aligned on the center of the rectangle, starting from the center of each yoke branch, so that a field space is formed there. Cylinder coils are mounted on the pole shoes and face each other white being connected to an associated capacitor arrangement to form an oscillatory circuit.
The schematic representation of a magnetic field applicator to carry out the above-mentioned Hyperthermia process does not yet lead beyond the experimentation stage to a practical industrial solution as is required for the sake of favorable production and operating costs, minimal space requirement and low leakage field and optimal therapeutic effect for utilization under hospital conditions.
It is therefore the object of the present invention to create a magnetic field applicator to heal magnetic or magnetically substances or solids in biological tissue which would
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meet the above requirements with respect to industrial production for utilization under hospital conditions or other possibly industrial application.
Magnetic field applicator to heat magnetic or magnetizable substances or solids in
biological tissue, with a magnetic yoke with two pole shoes facing each other on the
magnetic yoke and separated by a gap in the exposure volume and with two magnetic
coils for the production of a magnetic alternating field, each of which is assigned to a
pole shoe, wherein the magnetic yoke . and the pole shoes v , consist offerrite
building blocks-\ , mounted together and in that the magnetic coils ) are
disk coils with at least one winding extending helicoidally, each assigned to a pole shoe, and in that the respective pole shoe ends comprise a surrounding magnetic coil/pole shoe gap (a) between them.
According to invention the magnetic yoke and the pole shoes consist of assembled ferric building blocks which are mounted together. The magnetic coils are disk coils with at least one helicoidally extending winding each of which is assigned to a pole shoe and comprises the appertaining pole shoe end with an intermediate, surrounding magnetic coil pole shoe gap.
For hyperthermia, in particular with magnetic liquids, alternating field forces of approximately 15 to 20 kA/m at approx. 50 to 100 kHz are required. With a volume exposed by a magnetic field of 8 to 301, effective power of approx. 18 kW to 80 kW must be produced by a hyperthermia installation. This energy must be produced in form of high-frequency and must then be transmitted in form of heat, since only a few watt are produced the magnetic fluid for the hyperthermia in a patient's body.
With the arrangement as discussed it is possible to keep the volume exposed by a magnetic field as well as the leakage fields advantageously small and to limit them to a therapy area in the patient's body, so that the required energy capacity and the requirements for heat transmission can be reduced. A magnetic yoke and pole shoes made of ferrite building blocks as well as the disk coil with at least one helicoidally
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winding contribute to this. Thanks to the special configuration of the magnetic coils combined with the surrounding magnetic coil/pole shoe gap undesirable excess flow density in combination with high losses are reduced considerably. By comparison with the proposed arrangement, the arrangement with cylinder coils around the pole shoes in the latter's last winding to the gap between two magnets by inductive heating for example, as indicated in the state of the art, produces high temperatures with considerable problems with heat removal. The disk-shaped coil design according to the invention, in combination with the magnetic-coil/pole shoe gap on the other hand. results in considerably lower flow densities on the surrounding edge of the assigned pole shoes.
The utilization of ferrite building blocks in combination with the high alternating frequency of approx. 50 to 100 kHz makes possible an advantageous limitation of the volume exposed by a magnetic field, whereby only about 1/2000 of the energy which would have an equivalent air volume is moved in the ferrite volume. This considerable advantage is accompanied by the fact that the ferrite building blocks are prone to losses, whereby e.g. a doubling of the flow density in the work area can already result in 5 to 6 times greater losses. For this reason appropriate measures are indicated below in order to keep the flow density low, and in particular to avoid undesirable flow density increases or to at least reduce them considerably.
Ferrites are ceramic-like building blocks that can be produced in any desired form at reasonable cost, in particular not in the overall form of the magnetic yoke used here. For this reason the invention proposes that the magnetic yoke be composed of ferrite building blocks, whereby disturbances in a flow that should be as even as possible may occur at transition points. Advantageous solutions for the management of these problems are indicated further below.
The magnetic field applicator according to the invention is equally well suited to carry out hypothermia treatments as thermo-ablation procedures. In addition the magnetic field applicator according to the invention is suitable to warm other substances or solids for medical applications other than in cancer therapy. Among the latter are all the heat-related medical applications such as heat-induced implant or stem regeneration, implant
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or stent surface activation, heating of inflamed body areas not affected by cancer for therapeutic purposes, facilitating contrast media distribution or improvement through magnetic alternating field excitation of super-paramagnetic contrast media, the mobilization of molecular-biological, cell-biological and development-physiological processes through excitation of magnet-carrier-assisted gene transfer systems, legends, receptors, transmitters, other signal molecules as well as the triggering of material metabolism processes and endocrinal processes.
In a practical embodiment of the invention the magnetic coils should have one or more windings which extend helicoidally and are made of spun copper-strand wire in order to minimize eddy current losses as much as possible.
In an especially advantageous embodiment of the invention, the pole shoes are made cylindrically or round, as seen from the top, whereby they face each other with parallel pole shoe circles pointing to each other at a distance from the gap in the exposure volume. Accordingly, the magnetic coils are then made in form of circular rings. This evens out the magnetic flow accompanied by a reduction of heating which would otherwise be increased at spatial corners and edges.
Especially favorable conditions with respect to energy and flow are derived, when the disk-shaped magnetic coil is placed as close as possible to the gap in the exposure volume, in particular in a flush-surface arrangement of the assigned pole shoe surface. Additional optimization is achieved if the magnetic pole/pole shoe gap measures approximately 1/10 of the diameter of the pole shoe (0.07 to 0.1 times) and if the surrounding edge of the corresponding pole shoe surface is rounded off. In this manner damaging flow density excesses are reduced considerably.
According to present invention, the pole shoe diameter should be greater than the width of the gap in the exposure volume. Thereby leakage fields outside the pole shoes or of the volume exposed by a magnetic field are reduced, so that the flow density in the ferrite building blocks, and therefore the losses in the ferrite material can be kept at a
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relatively low level. If pole shoes with relatively small cross sections were used, these losses in the ferrite building blocks would be disproportion ally high.
According to present invention, the magnetic yoke is composed of square ferrite building blocks with surfaces ground plane-parallel to created uniform transitions, whereby possibly outer sintering layers are removed. The round pole shoes are accordingly composed of wedge-shaped ferrite building blocks like pieces of a cake. with adjoining surfaces also ground to be plane-parallel in this case.
In order to lower eddy current losses, invention proposes that the cut-stone-shaped ferrite building blocks be made of ferrite plates lined up in a row, each of them separated from the other by an isolation cooling gap. In the mounted state, these ferrite plates are aligned along the magnetic flow. Magnetic field applicator in that cut-stone-shaped ferrite building blocks consist of ferrite plates lined up in a row in the magnetic yoke along the direction of magnetic flow and separated from each other perpendicularly to the magnetic flow by insulation/cooling gap through which cooling air can be conveyed and which adjoin each other along the direction of magnetic flow via narrow contact gaps S2. To produce one-piece ferrite building blocks from ferrite plates these are separated from each other by means of plastic separators and are glued to each other via the separators. Magnetic field applicator wherein plastic separators are inserted into the insulation/cooling gap preferably in lateral areas, and in that the ferrite plates are bonded via the separators into cut-stone-shaped ferrite building blocks as yoke elements.
Similarly the wedge-shaped ferrite building blocks are produced to form the pole shoes, whereby a tubular central bore is left open through which cooling air can be introduced. To bond the ferrite plates, a temperature-resistant two-component adhesive is preferably used Magnetic field applicator separators are inserted between wedge-shaped ferrite building blocks in order to constitute insulation/cooling gaps, whereby the adjoining ferrite building blocks may be bonded together into a pole shoe via said separators, and in that an axial tubular opening is provided to constitute a tubular pole shoe and in that cooling air can be introduced through the opening.
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The gaps between the ferrite plates serve for electrical insulation as well as for cooling, in that cooling air is blown through the gaps. Cooling is necessary, as in spite of the ferrite's low conductivity, relative great eddy currents are produced and the heat that this produces must be removed. Although liquid cooling would be more effective, this cannot be done because of the insulation requirements. Oil cooling is dangerous because of the flammability of oil, and equivalent non-flammable liquids generally contain toxins. Generally speaking, the density problem, especially with a movable yoke element in combination with the other technical difficulties could only be solved at high cost if a liquid coolant were used.
In a preferred embodiment of the invention, the magnetic yoke consists ofatleast one vertical yoke and two connected transversal yoke elements, whereby the pole shoes facing each other are connected to the transversal yoke elements. At least one yoke element is adjustable relative to the other yoke element to change the width of the gap in the exposure volume. As explained earlier, the volume exposed by a magnetic field should be kept as low as possible to ensure overall favorable conditions. In a design with the movable transversal yoke elements this can be achieved in that in order-to easily place a patient, for example, within the gap in the exposure volume the pole shoe distance is enlarged by moving at least one transversal yoke element and is subsequently reduced once more as much as possible for the exposure to a magnetic field.
As was indicated earlier, the magnetic flow is on the one hand controlled at the
transition points in such manner that the magnetically inactive sintering layers of
approximately 0.1 to 0.2 mm produced in the manufacturing process are removed, and
the magnetically conductive surfaces are in addition ground to be plane-parallel. Due to
the high permeability of ferrite, the least unevenness has an effect so that flow control
with forced-air gaps is advantageous. This is especially advantageous with forced-air
gaps of 2 to 3 mm at the transition points between the movable transversal yoke
elements and adjoining vertical yoke elements and/or at transition points between transversal yoke elements and the pole shoes. In the vicinity of such a relatively wide
forced-air gap a sintering layer may be left in a ferrite building block, depending on
conditions, in order to reduce the manufacturing costs. Magnetic field applicator where
in the forced-air gaps preferably with a gap width of 2 to 3 mm are provided for the
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control of the magnetic flow at tolerance-prone transition points between the magnetic
yoke building blocks, in particular at transition points between transversal yoke
elements; and vertical yoke elements which are adjustable relative to each
other and/or at transition points between transversal yoke elements and the pole
shoes > whereby the gap width of these forced-air gaps are very large
compared to the contact gaps x ,, in particular in the adjustment area of the transversal yoke.
In principle the magnetic yoke can be made in form of a C-arc in which the area of the C opening represents the gap in the exposure volume formed by the pole shoes. In this case the good accessibility of the poie shoes and of the magnetic coil and thereby of the entire gap in the exposure volume is advantageous. However, large leakage fields occur with a C arc and flow paths of different lengths for the closure of magnetic flux as well as deflection problems at the corners.
In especially preferred embodiment in the invention on the other hand has a magnetic yoke in form of an M, with a three-legged arrangement, with two parallel vertical yoke elements of identical geometry at a distance from each other and with two transversal yoke elements connected between them, on which pole shoes pointing at each other are installed with the magnetic coils in the central area.. One transversal yoke element with appertaining magnetic coil is designed so as to be a component adjustable relative to the other transversal yoke element for the adjustment of the width of the gap in the exposure volume. The closure of magnetic flux is advantageously subdivided on both sides into two paths of equal length and having the identical geometry. The mechanical aspects for the relative shifting of at least one transversal yoke element relative to a C magnetic yoke are easily implemented since the vertical yoke elements can be utilized as supports on either side.
According to invention a component consisting of a lower transversal yoke element and the associated pole shoe with magnetic coil is attached fixedly. A patient carriage with a patient support and carriage position display made of a plastic material can be attached On this fixed pole shoe for example, whereby the patient need not be moved any more
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during the adjustment of the width of the gap in the exposure volume. A portal consisting of the two vertical yoke elements of the upper transversal yoke element with associated pole shoe and magnetic coil can then be shifted relative to this fixed component by means of a vertical displacement device for the adjustment of the width of the gap in the exposure volume.
A vertical displacement device can be made in form of a simple linear drive attacking preferably at a vertical magnetic yoke element. For example, a self- inhibiting spindle drive can be used, so that the overall arrangement can be implemented very reliably and without danger that heavy magnetic yoke components may endanger a patient due to errors in the displacement device.
In an advantageous further development the magnetic yoke can be held in a supporting structure in which cooling air can be supplied and guided, whereby said cooling air then flows through the cooling-air gap of the ferrite components to the heat removal.
According to invention and depending on conditions and on special requirements, the gap in the exposure volume and thereby also the volume exposed by a magnetic Held can be delimited laterally by field delimiting coils and/or by bulkhead walls4ekrYU-HWj a slip in space and which may be vertically adjustable to each other.
In principle, the magnetic field applicator can be used for a precisely localized and contact-less hypothermia on all kinds of tissues- bodies, objects and masses to be provided with fields while using incorporated magnetic and/or magnetically substances for suitable purposes. However, a preferred application of the magnetic field applicators is in the area of medicine, in particular in cancer therapy whereby a magnetically liquid with magnetically nano - particles is preferably used as the substance, A tumor area is to be heated locally by this method to temperature values above 41'C.
According to invention magnetic alternating fields with magnetic field forces of approximately 10 to 15 kA/m and frequencies from approximately 50 to 100 kHz are
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used for this purpose. In combination with the magnetic field applicator claimed above, the temperatures required for a tumor therapy are then reached. For a thermo seed application of the magnetic field applicator. 1 to 2 kA/m are already sufficient. Depending on the given situations, frequencies in a wider frequencies, from 20 to 500 khz may also be suitable.
The invention is explained in further detail through a drawing.
Fig. 1 shows a schematic sectional view through a magnetic field applicator,
Fig. 2 shows a schematic top view on the magnetic field applicator of Fig. 1,
Fig. 3 show'-s a schematic side view of the magnetic field applicator of Fig.1.
Fig. 4 shows a top view on a pole shoe with wedge-shaped ferrite building blocks.
Fig. 5 shows a side view of the pole shoe of Fig. 4,
Fig. 6 schematically shows a perspective and enlarged representation of the structure of
the hewn-stone-shaped ferrite building blocks.
Fig. 7 schematically shows an enlarged representation of a transitional area between a
vertical yoke element and a transversal yoke element,
Fig. 8 schematically shows a side view of a magnetic coil flat and flush with a pole shoe
surface and
Fig. 9 schematically shows an alternative magnetic field applicator in form of a C arc.
Fig. 1 schematically shows a magnetic field applicator 1 for hyperthermia, in which a body into which a magnetic or rria^etkja-Uesubstance or solids can be introduced and for which fields are to be provided can be placed and can be irradiated. A tumor zone in a human body into which a liquid with e.g. magnetic nano-particles are incorporated is especially well suited as a body to be provided with fields, whereby the tumor zone can be heated to temperature values preferably above approx. 41 "C.
The magnetic field applicator 1 comprises a magnetic yoke 2 designed in an M shape in form of a three-legged arrangement and is provided with two parallel vertical yoke elements 3, 4 at a distance from each other as well as with two transversal yoke elements 5, 6 connected between them.
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A component consisting of the lower transversal yoke element 6 and its associated lower pole shoe 8 with lower magnetic coil is installed fixedly. Relative to it, a portal consisting of the two vertical yoke elements 3, 4, the connected upper transversal yoke element 5 and its associated upper pole shoe 7 with upper magnetic coil 9 can be displaced by means of a self-inhibiting spindle drive 11 shown only schematically here, in order to adjust the width of the gap in the exposure volume 12.
It can furthermore seen in Fig. 1 that the gap in the exposure volume 12 is delimited by bulkheads 14, 15 which delimit a slip-in space 13. The bulkheads 14, 15 can in this instance be adjusted vertically relative to each other.
As can be seen especially also in Fig. 8, the upper magnetic coil 9 and the lower magnetic coil 10 are made in form of disk coils with one or several windings which extend helicoidally and are made of stranded copper wires.
Fig. 8 furthermore shows that the magnetic coils 9, 10 comprise the pole shoe ends with an intercalated and surrounding magnetic coil/pole shoe gap (a). As can be seen especially in Fig. 4, which shows atop view of one of the pole shoes 7, 8, the pole shoes 7, 8 are designed in a circular form. The magnetic coil/pole shoe gap (a) is of a magnitude range of 0.07 to 0.1 times the pole shoe diameter (d), whereby the magnetic coil is approximately flush-surface with the pole shoe end surface, and the surrounding edge is rounded off at the pole shoe end surface.
Furthermore the size of the gap in the exposure volume 12 is also designed in function of the pole shoe diameter (d) in order to reduce the leakage fields. Thus the pole shoe diameter (d) is greater than the gap in the exposure volume 12 in a preferred embodiment in order to avoid leakage fields.
As can be seen in Figs. 2 and 3, respectively showing a lateral view and a top view1 of the magnetic yoke 2, the magnetic yoke 2 is composed of cut-stone-shaped ferrite building blocks 16, the surfaces of which are freed of sintering layers and are ground
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plane-parallel. These cut-stone-shaped ferrite building blocks 16 are in turn placed in a row, as shown in Fig. 6, and are made up of ferrite plates 18 aligned in the magnetic yoke 2 in the sense of direction of flow 17.
These ferrite plates 18 are separated from each other transversally to the direction of flow 17 by insulation cooling gap 19. In lateral areas plastic separators 20 are inserted in this insulation/cooling gap 19, whereby the ferrite plates 18 are bonded via these plastic separators 20.to the cut-stone-shaped ferrite building blocks 16 as yoke elements.
Cooling air can be conveyed through the insulation/cooling gap 19 to cool the magnetic yoke 2 as shown schematically in Fig. 6 by means of arrow 21.
In Figs. 4 and 5 it can be seen that the round pole shoes 7, 8 are composed of ferrite building blocks 22 which are wedge shaped as seen from the top the surfaces of which are also freed of sintering layers and are ground plane-parallel. Separators are also inserted between the wed se-shaped ferrite building blocks 22 to form insulation/cooling gaps 23 shown merely schematically, and adjoining ferrite building blocks are bonded to each other via these separators. The separators are not shown in the schematic representations of Figs. 4 and 5.
It can furthermore be seen in Figs. 4 and 5 that the ole shoes 7, 8 have an axial, tubular opening 24 through which the cooling air can be introduced into the magnetic field applicator 1, as can especially be also seen in Fig.I.
Fig. 7 shows that the cut-stone-shaped ferrite building blocks 16 adjoin each other along the magnetic flow direction 17 over only a very narrow contact gap (S2). As can also be seen in Fig. 7, forced-air gaps (S|) are provided in particular at the transition points between the vertical yoke elements 3, 4 which are adjustable relative to the lower transversal yoke element 6 as well as at the transition points between the transversal
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yoke elements 5, 6 and the pole shoes 7, 9 for advantageous control of the magnetic flow.
These forced-air gaps (SI) has a gap width of e.g. 2 to 3 mm and are very large by comparison to the contact gaps (S2).
The magnetic field is produced b the magnetic coils 9. 10 which are connected to a capacitor, not shown here, into an oscillatory circuit in which the energy then oscillates as an idle power at the resonance frequency of the circuit. The magnetic field forces are preferably in a range of 1 to 20 kA/m while the frequencies are preferably in a range of 20 lo 500 kHz. For a thermo seed application of the magnetic field applicator. 1 to 2 kA/m are sufficient, while higher field forces are necessary with application w.-ith magnetic fluids.
Fig. 9 finally shows an alternative embodiment of a magnetic yoke 25 in form of a C arc. This C arc comprises a vertical yoke element 26 and an upper transversal yoke element 27 as well as a lower transversal yoke element 28. With the exception of outer form, the magnetic yoke 25 is basically constructed with the same components as the magnetic yoke 2, so that the same parts are designated with the same references. Thus the vertical yoke element 26. the upper transversal yoke element 27 and the lower transversal yoke element 28 are constructed of cut-stone-shaped ferrite building blocks 16 and the magnetic yoke 25 comprises pole shoes 7, 8 with their respectively assigned magnetic coils 9, 10. A C-arc of this type has the advantage of good accessibility but has the disadvantage that a larger leakage field is produced with it.
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WE CLAIM :

1. Magnetic field applicator to heat magnetic or magnetizable substances or solids
in biological tissue,
with a magnetic yoke with two pole shoes facing each other on the magnetic yoke and separated by a gap in the exposure volume and
with two magnetic coils for the production of a magnetic alternating field, each of which is assigned to a pole shoe,
wherein
the magnetic yoke (2:25) and the pole shoes (7, 8) consist of ferrite building blocks (16, 22 ) mounted together and
in that the magnetic coils (9, 10) are disk coils with at least one winding extending helicoidally, each assigned to a pole shoe, and in that the respective pole shoe ends comprise a surrounding magnetic coil/pole shoe gap (a) between them.
2. Magnetic field applicator as claimed in claim 1, wherein the magnetic coils (9, 10 ) have one or several windings extending helicoidally and made of stranded copper wires.
3. Magnetic field applicator as claimed in claim 1 or claim 2, wherein
the pole shoes (7, 8 ) are circular in shape as seen from above and face each other with circular parallel pole shoe surfaces pointing to each other at a distance of the gap in the exposure volume (12) and in that the magnetic coils (9, 10) are accordingly made in form of a circular ring.


Magnetic field applicator as claimed in one of the claims 1 to 3, wherein
the magnetic coil/pole shoe |ap (a) size is in the range of 0.07 to 0.1 times the pole shoe diameter (d) and
in that the magnetic coil(7, 8)is approximately flush with its surfaces with respect to the surface of the pole shoe end, whereby the surrounding edge is rounded off at the pole shoe end surface.
5. Magnetic field applicator as claimed in one of the claims I to 4, wherein pole shoe diameter (d) is greater than the sap in the exposure volume (12).
6. Magnetic field applicator as claimed in one of the claims 1 to 5, wherein
the magnetic yoke (2; 25) is composed square of cut-stone-shaped ferrite building blocks 16 the surfaces of which could be freed of sintering layers and are ground plane- parallel and
in that round pole shoes (7, 8 )are composed of ferrite building blocks (22) suitably machined to wedge-shaped as seen from above.
7. Magnetic field applicator as claimed in one of the claims 1 to 6, wherein
cut-stone-shaped ferrite building blocks (16)consist of ferrite plates (18) lined up in a row in the magnetic yoke (2; 25) along the direction of magnetic flow and separated from each other perpendicularly to the magnetic flow by insulation/cooling gap(19)through which cooling air can be conveyed and which adjoin each other along the direction of magnetic flow via narrow contact gaps S2
8. Magnetic field applicator as in claim 7, wherein plastic separators (20) are
inserted into the insulation/cooling gap 19, preferably in lateral areas, and in that
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the ferrite plates (18 ) are bonded via the separators (20) into cut-stone-shaped ferrite building blocks (16 ) as yoke elements.
9. Magnetic field applicator as claimed in claim 6, wherein
separators are inserted between wedge-shaped ferrite building blocks (22) in order to constitute insulation/cooling gaps (23), whereby the adjoining ferrite building blocks (22 ) may be bonded together into a pole shoe via said separators, and
in that an axial tubular opening is provided to constitute a tubular pole shoe (7, 8) and in that cooling air can be introduced through the opening (24).
10. Magnetic field applicator as claimed in one of the claims 1 to 9, wherein
the magnetic yoke (2; 25 )consists of at least one vertical yoke element (3, 4: 26) and to transversal yoke elements (5, 6: 27, 28 )connected to same and
the pole shoes (7, 8 ) facing each other are connected to the transversal yoke elements (5, 6; 27, 28 ) whereby
at least one transversal yoke element (6) can be adjusted relative to the other transversal yoke element (5) to change the width of the gap in the exposure volume.
11. Magnetic field applicator as claimed in one of the claims 1 to 10, wherein
forced-air gaps (S1), preferably with a gap width of 2 to 3 mm are provided for the control of the magnetic flow at tolerance-prone transition points between the magnetic yoke building blocks, in particular at transition points between transversal yoke elements (6) and vertical yoke elements (3, 4 ) which are adjustable relative to each other and/or at transition points between transversal yoke elements (5, 6) and the pole shoes (7, 8) whereby the gap width of these
I9

forced-air gaps (Si) are very large compared to the contact gaps (S2), in particular in the adjustment area of the transversal yoke.
12. Magnetic field applicator as claimed in one of the claims 1 to 11, wherein the magnetic yoke(25)is made in form of a C arc in which the zone of the C opening represents the gap in the exposure volume formed by the pole shoes.
13. Magnetic field applicator as claimed in one of the claims 1 to 11, characterized in that the magnetic yoke (2) is made in an M shape as a three-legged arrangement, with two parallel vertical yoke elements (3, 4) at a distance from each other and having the same geometry, and with two transversal yoke elements (5, 6) between them and with pole shoes (7, 8) facing each other and located in their center, and of these at least one transversal yoke element(6)with connected pole shoe (8) and assigned magnetic coil (10) can be adjusted as a component relative to the other transversal yoke element(5) in order to adjust the width of the gap in the exposure volume.
14. Magnetic filed applicator as per claim 13 wherein the fact that a module made up of lower transverse yoke part(6)and allocated pole shoe(8)with magnetic spool (10) is permanently fixed, and that as against this a port made up of both vertical yoke parts (3, 4) and upper transverse yoke part (5) and allocated pole shoe(7)with magnetic spool(9)is adjusted by means of a vertical adjusted fitting(11)for setting the field gap size.
15. Magnetic field applicator as claimed in claim 14, wherein the vertical adjustment device consists of at least one motor-controlled linear drive moving the vertical yoke elements (3, 4 )from below, consisting in particular of a self-inhibiting spindle drive (11).
16. Magnetic field applicator as claimed in one of the claims 1 to 15, wherein the magnetic yoke (2; 25) is held in a support assembly into which cooling air can be caused to flow.


17. Magnetic field applicator as claimed in one of the claims 1 to 16, wherein the gap in the exposure volume 12 is delimited laterally to the vertical yoke elements (3, 4; 26 ) by field delimitation coils and/or by adjustable bulkheads (14, 15) delimiting a slip-in space and which may be vertically adjustable relative to each other,
Dated this 9th day of March, 2001,


Documents:

abstract1.jpg

in-pct-2001-00269-mum-cancelled pages(23-03-2005).pdf

in-pct-2001-00269-mum-claims(granted)-(23-03-2005).doc

in-pct-2001-00269-mum-claims(granted)-(23-03-2005).pdf

in-pct-2001-00269-mum-correspondence(ipo)-(10-02-2005).pdf

in-pct-2001-00269-mum-correspondence1(23-03-2005).pdf

in-pct-2001-00269-mum-correspondence2(23-03-2005).pdf

in-pct-2001-00269-mum-drawings(23-03-2005).pdf

in-pct-2001-00269-mum-form 1(9-03-2001).pdf

in-pct-2001-00269-mum-form 19(11-02-2004).pdf

in-pct-2001-00269-mum-form 2(granted)-(23-03-2005).doc

in-pct-2001-00269-mum-form 2(granted)-(23-03-2005).pdf

in-pct-2001-00269-mum-form 5(9-03-2001).pdf

in-pct-2001-00269-mum-form-pct-ipea-409(24-05-2004).pdf

in-pct-2001-00269-mum-form-pct-isa-210(24-05-2004).pdf

in-pct-2001-00269-mum-other documents(23-03-2005).pdf

in-pct-2001-00269-mum-petition under rule 137(13-04-2005).pdf

in-pct-2001-00269-mum-power of attorney(9-05-2001).pdf


Patent Number 207760
Indian Patent Application Number IN/PCT/2001/00269/MUM
PG Journal Number 32/2007
Publication Date 10-Aug-2007
Grant Date 22-Jun-2007
Date of Filing 09-Mar-2001
Name of Patentee MFH HYPERTHERMIESYSTEME GMBH
Applicant Address WIESENWEG 10, D-12247, BERLIN, GERMANY
Inventors:
# Inventor's Name Inventor's Address
1 FEUCHT, PETER FEURIGSTRASSE 54, D-10827 BERLIN, GERMANY,
PCT International Classification Number A61N 1/40
PCT International Application Number PCT/EP00/06836
PCT International Filing date 2000-07-18
PCT Conventions:
# PCT Application Number Date of Convention Priority Country
1 199 37 492.9 1999-08-07 Germany