Abstract: A method and apparatus for generating a localized heating are provided, the method comprising: transmitting a spatially localized or shaped electromagnetic field via a plurality of coils to a subject and generating magnetic resonance signals; performing magnetic resonance imaging based on the magnetic resonance signals to generate an image of a region of interest of the subject; and controlling the plurality of the same imaging coils to radiate radio frequency (rf) energy to generate the localized heating on a region of interest. The invention provide a more efficient manner for generating localized heating and means for verifying the heating pattern without the need to measure temperature rises in the patient. This is useful to check the localization prior to the application of hyperthermia.

Abstract: Method, system and apparatus for monitoring target tissue temperatures wherein temperature sensors are configured as passive resonant circuits each with a unique resonating signature at monitoring temperatures extending below a select temperature setpoint. The resonant circuits are configured with an inductor component formed of windings about a ferrite core having a Curie temperature characteristic corresponding with a desired temperature setpoint. By selecting inductor winding turns and capacitance values, unique resonant center frequencies are detectable. Temperature monitoring can be carried out with implants at lower threshold and upper limit temperature responses. Additionally, the lower threshold sensors may be combined with auto-regulated heater implants having Curie transitions at upper temperature limits.

Abstract: Method, system and apparatus for monitoring target tissue temperatures wherein temperature sensors are configured as passive resonant circuits each with a unique resonating signature at monitoring temperatures extending below a select temperature setpoint. The resonant circuits are configured with an inductor component formed of windings about a ferrite core having a Curie temperature characteristic corresponding with a desired temperature setpoint. By selecting inductor winding turns and capacitance values, unique resonant center frequencies are detectable. Temperature monitoring can be carried out with implants at lower threshold and upper limit temperature responses. Additionally, the lower threshold sensors may be combined with auto-regulated heater implants having Curie transitions at upper temperature limits.

Abstract: A method wherein, following a therapeutic radiation treatment, a heat dose is administered to the treated cells to decrease the damage caused by radiation exposure or a therapeutic agent.

Abstract: To realize a body surrounding solenoid-type body heating device with small coil impedance which can generate a magnetic flux of predetermined density to one part of the living body near the affected area in the solenoid coil, a body heating device 10 includes a cylindrical solenoid coil 17 in which the body can be inserted easily, a high-frequency power supply 11 to drive the solenoid coil, and a body holder 15 which can be inserted easily in the solenoid coil 17. In the body heating device 10, an across-body direction cross section of the solenoid coil 17 has an arched-shape over a half of the solenoid coil 17 in the peripheral direction and a straight-lined shape in the rest, and a secondary solenoid coil 21 with shorter length and coiled more densely than the solenoid coil 17 is inserted in the solenoid coil 17. A magnetic core 40 which can be inserted easily in the solenoid coil 17 is installed on the body holder 15.

Abstract: A method and system of magnetic hyperthermia control using ultrasound thermometry, the method comprising: acquiring a reference set of ultrasound data corresponding to a tissue of interest (121); applying a plurality of magnetic nanoparticles (210) at the tissue of interest (121); applying an electromagnetic field based on a set of operating parameters to initiate the hyperthermia; acquiring another set of ultrasound data corresponding to the tissue of interest (121); and determining a temperature change based on the reference set of ultrasound data and the other set of ultrasound data.

Abstract: Method, system and apparatus for carrying out a controlled heating of dermis to achieve a percentage of linear collagen shrinkage. Implants are employed which preferably are configured as a thermal barrier defining support of an outwardly disposed support surface which carries one or more heater segments. Located along heating channels at the interface between dermis and next adjacent subcutaneous tissue, the structure protects the latter from thermally induced damage while directing heat energy into the former.

Abstract: System method and apparatus for accurately carrying out the in situ heating of a targeted tissue. Small implants are employed with the targeted tissue which exhibit an abrupt change of magnetic permeability at an elected Curie temperature. The permeability state of the implant is monitored utilizing a magnetometer. The implants may be formed as a setpoint temperature determining component combined with a non-magnetic heater component to enhance the tissue heating control of the system. With the system, a very accurate quantum of heat energy can be supplied to a neoplastic lesion or tissue carrying infectious disease so as to maximize the induction of heat shock proteins. The system also may be utilized in conjunction with non-magnetic arterially implanted stents for the hyperthermia therapy treatment of restenosis and in conjunction with the mending of boney tissue.

Abstract: A therapeutic microwave system comprises a support unit having two or more separable segments; a microwave power assembly positioned between two separated segments of the support unit and including two or more microwave power supply devices; position adjustment componentry; and a central processing unit. The system may further include a temperature sensor for monitoring a treated subject's exhaled air temperature in real time and adjusting microwave irradiation accordingly, and a cooling device for controlling the patient's brain temperature during treatment.

Abstract: Devices for treating body tissue. The device includes: an elongated cylindrical guide portion having a distal end and a proximal end; and one or more heat generators securely attached to the elongated guide portion. The heat generators are operative to inductively generate heat energy in response to an electromagnetic field externally applied thereto. One or more of the heat generators are disposed near target tissue so that the heat energy generated by the heat generators is used to treat the target tissue during operation.

Abstract: System method and apparatus for accurately carrying out the in situ heating of a targeted tissue. Small implants are employed with the targeted tissue which exhibit an abrupt change of magnetic permeability at an elected Curie temperature. The permeability state of the implant is monitored utilizing a magnetometer. The implants may be formed as a setpoint temperature determining component combined with a non-magnetic heater component to enhance the tissue heating control of the system. With the system, a very accurate quantum of heat energy can be supplied to a neoplastic lesion or tissue carrying infectious disease so as to maximize the induction of heat shock proteins. The system also may be utilized in conjunction with non-magnetic arterially implanted stents for the hyperthermia therapy treatment of restenosis and in conjunction with the mending of boney tissue.

Abstract: A medical technology device has an x-ray CT imaging system and a magnet system for generation of a radio-frequency alternating magnetic field for treatment of a tumor injected with ferrite nanoparticles, the x-ray CT system and the magnet system being combined to form a unitary structure. Imaging and tumor therapy can be conducted with one apparatus, and the monitoring of the course of the tumor therapy is simplified.

Abstract: The present invention relates to the process of selectively exposing matter to a specific wavelength of electromagnetic energy in sufficient flux density per wavelength to cause or promote a desired effect. The process includes, but is not limited to, destroying, disinfecting, denaturing, disinfesting, disrupting, or dehydration of one or more of the substances present. More specifically, present invention relates to subjecting matter, which may contain a mixture of substances, to electromagnetic energy, in concurrence with its spectral properties to exploit the spectral differences within the substance or within a mixture of substances. Energies are applied to cause wavelength-dependent reactions resulting from differential absorption; this additional applied energy manifests itself in changes, or quantum transitions, in the vibrational, rotational, magnetic, and electronic states of the molecules.

Abstract: Problems to be solved: to provide a coil device and a magnetic field generating device with reduced energy loss that are suitable for use in the thermotherapy method. Means for solving the problem: a coil device according to the present invention can be used in a magnetic field generating device for the thermotherapy method in which a magnetic flux is irradiated to the patient to selectively heat a specific portion of the patient. Said coil device is a bread-shaped coil device having a current path extending in the shape of a spiral in a substantially same plane, said current path comprising a hollow cylindrical member (10) of a nonmagnetic material inside which a space is formed and a plurality of conductive wires (11, 12) covered with an insulation material on the peripheries thereof.

Abstract: The invention is directed to a novel method for reducing discomfort caused by transcutaneous stimulation. The novel method includes providing transcutaneous stimulation, reducing the transcutaneous stimulation at a first location, and substantially maintaining the transcutaneous stimulation at a second location. The transcutaneous stimulation may be created by electric and/or magnetic fields. The first location may be relatively proximate to the cutaneous surface and may comprise tissue, nerves and muscle. Also, the second location may be relatively deeper than the first location and include, for example, brain tissue that requires the transcutaneous stimulation for treatment purposes. The invention further may include locating a conductor on a treatment area and/or a transcutaneous stimulation device relative to the first location. In addition, the method may further include adjusting how much the transcutaneous stimulation is reduced at the first location.

Abstract: The invention is directed to a novel method for reducing discomfort caused by transcutaneous stimulation. The novel method includes providing transcutaneous stimulation, reducing the transcutaneous stimulation at a first location, and substantially maintaining the transcutaneous stimulation at a second location. The transcutaneous stimulation may be created by electric and/or magnetic fields. The first location may be relatively proximate to the cutaneous surface and may comprise tissue, nerves and muscle. Also, the second location may be relatively deeper than the first location and include, for example, brain tissue that requires the transcutaneous stimulation for treatment purposes. The invention further may include locating a conductor on a treatment area and/or a transcutaneous stimulation device relative to the first location. In addition, the method may further include adjusting how much the transcutaneous stimulation is reduced at the first location.

Abstract: A composition of microscopic devices utilizable in a medical diagnostic or therapeutic procedure. Each microscopic device includes a nanostructure provided with a ligand for effectively coupling the nanostructure to a predetermined chemical or molecular site. A medical method in part comprises inserting the medical devices into a patient, attaching the nanostructures via the respective ligands to instances of a predetermined type of target structure inside the patient, and thereafter activating the nanostructures to perform a preselected medical diagnostic or therapeutic function.

Abstract: A virtual ablation electrode assembly includes a non-conductive outer cap fitted over an inner electrode to form a fluid chamber between a cap inner surface and an exterior surface of the electrode. The inner electrode includes an interior fluid trunk and one or more fluid distribution branches extending from the fluid trunk to the exterior surface. A plurality of pores extends between the cap inner surface and a cap outer surface. When the electrode is energized and when fluid is delivered through the one or more fluid distribution branches from the trunk, the conductive fluid fills the fluid chamber and flows out from the chamber through the plurality of pores of the cap establishing ionic transport of ablation energy from the inner electrode to a target site in close proximity to the cap.

Abstract: System method and apparatus for accurately carrying out the in situ heating of a targeted tissue. Small implants are employed with the targeted tissue which exhibit an abrupt change of magnetic permeability at an elected Curie temperature. The permeability state of the implant is monitored utilizing a magnetometer. The implants may be formed as a setpoint temperature determining component combined with a non-magnetic heater component to enhance the tissue heating control of the system. With the system, a very accurate quantum of heat energy can be supplied to a neoplastic lesion or tissue carrying infectious disease so as to maximize the induction of heat shock proteins. The system also may be utilized in conjunction with non-magnetic arterially implanted stents for the hyperthermia therapy treatment of restenosis and in conjunction with the mending of boney tissue.

Abstract: An induction heating apparatus includes a first interventional device and a second interventional device. The first interventional device includes an electrically conductive material. The first interventional device is adapted for implantation inside a body and for receiving an alternating current. The second interventional device comprises a magnetically conductive material. The second interventional device is adapted for implantation inside the body in close proximity to the first interventional device. With both devices placed inside the body, the second interventional device magnetically couples with the first interventional device and the second interventional device generates heat upon the application of the alternating current to the first interventional device thereby heating the body site.

Abstract: Systems for RF diathermy treatment are described. An apparatus includes an RF diathermy coil assembly, comprising: an elastically deformable garment; and a conductive coil assembly secured to the garment, including: a primary winding; and a secondary winding coupled to the primary winding, the primary winding and the secondary winding being configured to optimize an impedance match between the conductive coil and an RF power source connected to the conductive coil.

Abstract: System method and apparatus for accurately carrying out the in situ heating of a targeted tissue. Small implants are employed with the targeted tissue which exhibit an abrupt change of magnetic permeability at an elected Curie temperature. The permeability state of the implant is monitored utilizing a magnetometer. The implants may be formed as a setpoint temperature determining component combined with a non-magnetic heater component to enhance the tissue heating control of the system. With the system, a very accurate quantum of heat energy can be supplied to a neoplastic lesion or tissue carrying infectious disease so as to maximize the induction of heat shock proteins. The system also may be utilized in conjunction with non-magnetic arterially implanted stents for the hyperthermia therapy treatment of restenosis and in conjunction with the mending of boney tissue.

Abstract: A method and device to treat cardiovascular vulnerable plaque is provided by heating an implanted structure placed adjacent to a vulnerable plaque tissue to conduct heat into the vulnerable plaque tissue for a period of time. In a preferred embodiment, the implanted structure is a stent-like structure (SLS), and the heating of the implanted structure is a non-invasive inductive heating. The detecting of the vulnerable plaque tissue can be accomplished by techniques, such as Magnetic Resonance Imaging (MRI), infrared spectroscopy, thermography, blood tests, ultrasound, and X-ray, etc.

Abstract: Provided herein are methods, devices and compositions to conductively or to inductively heat substrates using electromagnetic energy. Also provided are methods, devices and compositions to inductively alter or treat a substrate by inducing a conformational change in the compositions and/or the substrates. The compositions provided comprise an energy absorbing species to transduce heat to the substrates to effect such alterations or treatments.

Abstract: Method, system and apparatus for monitoring target tissue temperatures wherein temperature sensors are configured as passive resonant circuits each, with a unique resonating signature at monitoring temperatures extending below a select temperature setpoint. The resonant circuits are configured with an inductor component formed of windings about a ferrite core having a Curie temperature characteristic corresponding with a desired temperature setpoint. By selecting inductor winding turns and capacitance values, unique resonant center frequencies are detectable. Temperature monitoring can be carried out with implants at lower threshold and upper limit temperature responses. Additionally, the lower threshold sensors may be combined with auto-regulated heater implants having Curie transitions at upper temperature limits.

Abstract: A method of treating a food object in an electrostatic field to thaw food rapidly at temperatures between 0° C. and a freezing temperature of an object to be treated. By applying the electrostatic field, the freezing temperature of the food is lowered but the food does not freeze in the electrostatic field. Accordingly, foods are kept fresher longer and the freshness can be maintained over a range of temperatures.

Abstract: An induction heating apparatus includes a first interventional device and a second interventional device. The first interventional device includes an electrically conductive material. The first interventional device is adapted for implantation inside a body and for receiving an alternating current. The second interventional device comprises a magnetically conductive material. The second interventional device is adapted for implantation inside the body in close proximity to the first interventional device. With both devices placed inside the body, the second interventional device magnetically couples with the first interventional device and the second interventional device generates heat upon the application of the alternating current to the first interventional device thereby heating the body site.

Abstract: A system and method for approaching the intervertebral disc through a percutaneous insertion from the back of a patient for thermal or electromagnetic treatment of an intervertebral disc, includes an elongated probe member having a guidable region adjacent its distal end with an undulating groove defined in its outer surface. The undulating groove is dimensioned to facilitate bending of the guidable region in at least one radial direction of movement relative to a longitudinal axis of the thermal probe. Preferably, the guidable region includes a plurality of undulating grooves, whereby adjacent undulating grooves are longitudinally spaced with respect to each other. The undulating grooves each define a sinusoidal configuration which may be arranged about an undulating axis extending in oblique relation to the longitudinal axis. The guidable region also includes a longitudinally extending backbone which resists bending of the guidable region in a radial direction of movement.

Abstract: A magnetic field applicator to heat magnetic substances in biological tissue, having a magnetic yoke with two pole shoes across from each other and separated from each other by a distance that defines the magnetic field exposure volume produced by the applicator, and with two magnetic coils, one assigned to each of the two pole shoes, to produce a magnetic field. The magnetic yoke and the pole shoes consist of ferrite segments assembled together. The pole shoes oppose each other and are surrounded by magnetic disk-shaped coils with one or more windings extending helicoidally, which creates an intermediate air gap between the pole shoes and coils. This results in a magnetic field applicator with the ability to effectively and efficiently administer hyperthermia and thermo-ablation procedures to destroy cancerous tissue in a patient, as well as having uses in other medical and industrial applications.

Abstract: A system and method for ablating a selected portion of a contact surface of biological tissue is provided. The system includes an elongated ablation sheath having a preformed shape adapted to substantially conform a predetermined surface thereof with the contact surface of the tissue. The elongated ablation sheath includes a non-permeable portion. The ablation sheath defines an ablation lumen sized to slideably receive an elongated ablative device longitudinally therethrough. The ablative device includes a flexible ablation element selectively generating an ablative field sufficiently strong to cause tissue ablation. Advancement of the ablation element slideably through the ablation lumen of the ablation sheath selectively places the ablation element along the ablation path for guide ablation on the contact surface when the predetermined surface is in strategic contact therewith.

Abstract: System method and apparatus for accurately carrying out the in situ heating of a targeted tissue. Small implants are employed with the targeted tissue which exhibit an abrupt change of magnetic permeability at an elected Curie temperature. The permeability state of the implant is monitored utilizing a magnetometer. The implants may be formed as a setpoint temperature determining component combined with a non-magnetic heater component to enhance the tissue heating control of the system. With the system, a very accurate quantum of heat energy can be supplied to a neoplastic lesion or tissue carrying infectious disease so as to maximize the induction of heat shock proteins. The system also may be utilized in conjunction with non-magnetic arterially implanted stents for the hyperthermia therapy treatment of restenosis and in conjunction with the mending of boney tissue.

Abstract: A magnetic material having a magnetic heating efficiency of at least 4.5×10−8 J.m/A.g in a cyclic magnetic field where the product of the amplitude and frequency of the applied field is less than or equal to 5×108 A/m.s, and the frequency of the applied filed is at least 20 kHz. The ideal magnetic material is characterized by a perfectly rectangular hysteresis loop, i.e. loop squareness of 1, with coercivity of 25 kA/m or less and high saturation magnetization. Preferably the magnetic material has a predominately cubic magnetic crystalline anisotropy. Preferably the magnetic material is a substituted magnetite (Fe3O4) or &ggr;-ferric oxide (&ggr;Fe2O3) crystalline lattice in which some of the iron atoms in that crystalline lattice have been substituted for one or more alternate metals atoms. Desirably, the metal atom is a member of the group: cobalt, zinc, nickel, manganese, magnesium, copper, chromium, gallium, cadmium.

Abstract: System method and apparatus for accurately carrying out the in situ heating of a targeted tissue. Small implants are employed with the targeted tissue which exhibit an abrupt change of magnetic permeability at an elected Curie temperature. The permeability state of the implant is monitored utilizing a magnetometer. The implants may be formed as a setpoint temperature determining component combined with a non-magnetic heater component to enhance the tissue heating control of the system. With the system, a very accurate quantum of heat energy can be supplied to a neoplastic lesion or tissue carrying infectious disease so as to maximize the induction of heat shock proteins. The system also may be utilized in conjunction with non-magnetic arterially implanted stents for the hyperthermia therapy treatment of restenosis and in conjunction with the mending of boney tissue.

Abstract: A method of positioning on a microwave waveguide a sensor (20) including an elongate metallic element (23, 24) comprising: selecting a tubular waveguide (12); determining the general orientation of the magnetic field (3) generated during microwave transmission; and positioning the elongate metallic element (20, 23, 24) substantially parallel to the orientation of the magnetic field (3). Connections (23, 24) of the sensor (20) extend longitudinally of the waveguide (12) and are connected to the outer wall (25) of the waveguide and the central conductor (16) of the coaxial cable (15) that powers the waveguide.

Abstract: A magnetic field applicator to heat magnetic substances in biological tissue, having a magnetic yoke with two pole shoes across from each other and separated from each other by a distance that defines the magnetic field exposure volume produced by the applicator, and with two magnetic coils, one assigned to each of the two pole shoes, to produce a magnetic field. The magnetic yoke and the pole shoes consist of ferrite segments assembled together. Additionally, the magnetic field applicator is composed of a magnetic yoke having two parallel vertical yoke elements of identical geometry spaced apart a distance from each other, and two transverse yoke elements disposed between said vertical yoke elements. The pole shoes, surrounded by disk-shaped magnetic coils, are attached to the center of said transverse yoke elements and oppose each other over a prescribed distance.

Abstract: The invention relates to nanoscale particles suited especially for use in tumor therapy by hyperthermia. Said particles comprise a (preferably superparamagnetic) iron oxide-containing core and at least two shells surrounding said core. The (innermost) shell adjoining the core is an envelope which comprises groups capable of forming cationic groups and is broken down by human or animal tissue at such a slow rate as to allow for association of the core surrounded by said envelope with the surface of cells and/or for absorption of said core into the inside of cells.

Abstract: Disclosed are therapeutic methods for the treatment of disease material involving administration of a thermotherapeutic magnetic composition, which contains single-domain magnetic particles attached to a target-specific ligand, to a patient and application of an alternating magnetic field to inductively heat the thermotherapeutic magnetic composition. Also disclosed are methods of administering the thermotherapeutic magnetic material composition. The thermotherapeutic methods may be used where the predetermined target is associated with diseases, such as cancer, diseases of the immune system, and pathogen-borne diseases, and undesirable targets, such as toxins, reactions associated with organ transplants, hormone-related diseases, and non-cancerous diseased cells or tissue.

Abstract: The invention concerns a probe for applying a high frequency electromagnetic energy flux on the skin through a mixture of conductive gel and a treatment product, designed to cause the treatment product to penetrate into the skin. The probe is provided with a non-conductive bearing surface (14), having a plurality of openings (6) around or in the proximity of which inductor elements (5) arranged in successive layers emit an electromagnetic field. The openings (6) emerge through an orifice (3) and contain the gel/treatment product mixture whereof the penetration into the skin is activated by the electromagnetic field. Advantageously, the probe further comprises at least one source of laser electromagnetic radiation (8) arranged inside or aligned with at least one opening (4) emerging in the bearing surface (14), so as to act jointly with the electromagnetic radiation emitted by the inductor element (5).

Abstract: A method of detecting and treating tumors within a subject is disclosed together with a process for the non-invasive measurement of tissue temperature within a subject.

Abstract: An active RF or microwave bandage, that incorporates any of various disclosed configurations of pliable planar microstrip or slotline antenna structures, is conformable to a selected area of the skin of a patient for use in therapeutically treating soft tissue of the patient underlying the selected area with pulsed electromagnetic field (PEMF) energy of a given frequency radiated from the planar antenna structure. The PEMF energy is supplied to the planar antenna structure by means including a PEMF generator (which generator may be a miniaturized portable generator employing a battery power supply that permits the patient being treated to be ambulatory).

Abstract: The present invention relates to catheter devices and methods for their use to modulate medical agents at selected locations in a patient's body.

Abstract: An apparatus for embolic treatment including a high frequency power source and at least one induction coil connected to the high frequency power source which is positioned around the vicinity of diseased vasculature of the body of a patient for generating an eddy current in the metallic coil inserted into the vascular malformation of the diseased vasculature. The eddy current in the metallic coil generates heat which coagulates and contracts the vascular malformation.

Abstract: The invention provides a system for treating tissue that includes a power measurement device, a flow rate controller coupled to the power measurement device, and an electrosurgical device configured and arranged to provide radio frequency power and conductive fluid to the tissue, wherein the flow rate controller is configured and arranged to modify a flow rate of the conductive fluid to the tissue, based on signals from the power measurement device. The invention also provides methods and devices for modifying flow rate of conductive fluid to tissue based on measurement of radio frequency power delivered to the tissue.

Abstract: A method is disclosed for forming and contracting scar collagen below a tissue surface in a selected tissue site. An electromagnetic energy apparatus is provided and includes an electromagnetic energy source and a delivery device. The delivery device is positioned on the tissue surface. Electromagnetic energy is produced from the electromagnetic energy source and delivered through the tissue surface to the selected tissue site for a sufficient time to induce scar collagen formation in the selected tissue site. No more than a second degree burn is formed on the tissue surface. The scar collagen is then contracted. This method is particularly useful in tissue sites that are devoid or deficient in collagen.

Abstract: A method for site specific treatment of diseased tissue in a patient, comprising the steps of: (i) selecting at least a magnetic material which has a magnetic heating efficiency of at least about 4.5.times.10.sup.-8 J.m./A.g, when magnetic field conditions are equal to or less than about 7.5.times.10.sup.7 A/s; (ii) delivering the magnetic material to diseased tissue in a patient; and (iii) exposing the magnetic material in the patient to a linear alternating magnetic field with a frequency of greater than about 10 kHz and a field strength such that the product of field strength, frequency and the radius of the exposed region is less than about 7.5.times.10.sup.7 A/s to generate hysteresis heat in the diseased tissue.

Abstract: In the present invention, a surgical trocar is adapted to inductively couple electrosurgical energy to specially adapted cordless electrosurgical instruments. In one embodiment of the present invention, an electrosurgical trocar includes a cannula, an inductive electrosurgical adapter and a locking connector adapted to connect the cannula to the inductive electrosurgical adapter. The cannula is an elongated tube which may be inserted into a body cavity, duct or vessel. The inductive electrosurgical adapter includes a housing with an elongated central aperture, a primary inductor coil positioned around and extending axially along the elongated aperture, first and second inductor leads, first and second conductors, an outer housing and an electrical cord.

Abstract: Microwave heating apparatus for fixating tissue comprises an electrically conductive waveguide structure having opposite first and second walls each of which has opposite first and second ends and a longitudinal centerline. A body of non-magnetic dielectric material inside the waveguide structure bridges the first and second walls preferably at their centerlines. A pocket extends through a wall of the waveguide structure into the body and a tissue holder containing contents, namely a tissue sample and a fixation solution, is arranged to be received in the pocket. The dielectric constant of the body is selected to closely match the composite dielectric constant of the tissue holder and its contents so that when microwave power is delivered into the waveguide structure for heating a succession of samples, variations in the dielectric properties of the different samples will not significantly affect the tuning of the waveguide structure.