WO2011084957A1

WO2011084957A1 - Medical heating device and method with self-limiting electrical heating element

Info

Publication number: WO2011084957A1
Application number: PCT/US2011/020136
Authority: WO
Inventors: Tai C. Cheng; Elbert T. Cheng; Jacqueline T. Cheng
Original assignee: Curo Medical, Inc.
Priority date: 2010-01-05
Filing date: 2011-01-04
Publication date: 2011-07-14
Also published as: KR20120117019A; BR112012016579A2; JP2013516281A; EP2521503A1; CN102811676B; KR101844086B1; JP6054748B2; CN102811676A; EP2521503A4; JP2017012862A

Abstract

Miniaturized, handheld medical heating devices utilize an electrical heater formed from a self-limiting conductive material, such as a conductive polymer or ceramic. The material has an electrical resistance that gradually changes with temperature such that heat production from electrical current through the material varies the resistance. A thermally insulating jacket contains the self-limiting heater element, which can be coupled to an electrical power supply. In one embodiment, a probe thermally coupled to the heater extends outward from the jacket. In another embodiment, the self-limiting conductive material is in series with one electrode of an electrode pair (or three electrodes) adapted to deliver radio frequency energy to tissue.

Description

PATENT

Attorney Docket No.: 028486-0002 lOPC

MEDICAL HEATING DEVICE AND METHOD WITH SELF-LIMITING

ELECTRICAL HEATING ELEMENT

[0001] This application is a continuation-in-part of application no. 12/652,626 (Attorney Docket No. 028486-000100US), filed on January 5, 2010, and of application no. 12/783,714 (Attorney Docket No. 078486-000200US), filed on May 20, 2010, the full disclosures of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention. This invention relates generally to medical devices and methods and more particularly to medical heating devices comprising a probe that causes heating of target tissue for tissue ablation, tissue cutting, or tissue shrinking, and to the energizing and control of such devices.

[0003] 2. Description of Related Art. Medical heating devices are presently used for tissue treatment and ablation in a number of treatment regimens. Typically, the heat is generated using radiofrequency-induced arcing between two points or by electric current conduction through the body to a grounding device. Such probes may cauterize tissue as they ablate, cut, or shrink the tissue. Cauterization is the process of sealing tissue using heat conduction from a metal probe heated by electric current where the heating stops bleeding from blood vessels in soft tissue. Relevant patents and publications of interest include U.S. Patent Nos.

4,026,300; 4,411,266; 5,190,517; 5,345,305; 5,554,679; 6,039,734; 6,132,426; 6,139,545; 6,312,392; 6,451 ,011 ; 6,770,072; 7,220,951 ; 7,309,849; 7,476,242; and 7,483,738; US Publication No. 2007/0167943; PCT Publication Nos. WO2006/009705 and

WO2008/014465; and Ramsay et al. (1985) Urol Res 13:99-102; Hernandez-Zendejas et al. (1994) Aesth Plas Surg 18:41-48; Utley et al. (1999) Arch Facial Plast Surg 1 :46-48; and Newman (2009), "Radiofrequency Energy for Denervation of Selected Facial Muscles:

Clinical Experiences at Six Months," The Internet Journal of Plastic Surgery, Volume 5, Number 2.

[0004] Electrosurgery is the application of a high-frequency, usually radiofrequency, electric current to tissue as a means to cut, coagulate, desiccate, or fulgurate tissue. Its benefits include the ability to make precise cuts with limited blood loss. Electrosurgery also includes surgical procedures where one or more localized portions of tissue are ablated using high frequency alternating current to generate heat, without heating other types of tissue near the target tissue. Electrosurgery devices use probe-like structures to physically contact the target tissue where such structure may be a type of electrode acting to pass electrical current to the tissue. Electrosurgery devices typically cause substantial physical damage to tissue.

[0005] One problem with electrosurgical (electric-arc-based) heating devices is the danger of electrical fires that can occur in a medical practice, operating suite, or hospital. Current conduction devices lack sufficient control over the path the current takes through the tissue from source to ground. The amount of tissue heating that occurs is also difficult to control, potentially leading to unnecessary injury as a side effect to the treatment.

[0006] Other types of medical heating devices use resistive electrical heating elements that are thermostatically controlled with switches or thermocouples. These devices control heat production and probe temperature essentially by switching the electrical heating element fully on or fully off, resulting in a temperature fluctuation of the ablation or cutting probe of the medical device that is more than optimal for tissue ablation or tissue cutting purposes.

[0007] A nerve is a cell that is relatively large. Each nerve cell contains a soma, multiple dendrites, an axon fiber, and multiple axon terminals. The soma is the central part of the nerve which contains the nucleus of the cell. The soma can range from 4 to 100 micrometers in diameter. The axon and dendrites are filaments that extend outward from the soma. Many dendrites typically surround and branch off from the soma, and have length of up to a few hundred microns. The axon is a single cable-like projection extending outward from the soma that can extend over 100 times the diameter of the soma. The axon carries

electrochemical nerve signals away from the soma to effectively control one or more muscles. Axon terminals are located opposite the soma-end of the axon. Typically, axon terminals terminate in a branch network of synapses, which release chemicals to

communicate with one or more muscles or other tissue or with other dendrites or soma from another nerve cell within a chain of nerve cells leading to one or more muscles or other tissue.

[0008] Typically, a large number of axons from many cells are bundled together in a large conduit called an epineurium, with other nested conduits inside. Analyzing the physiological structure of these conduits, we start with an inner conduit or sheath called an endoneurium, which directly surrounds each axon. Multiple axons are typically grouped together into fasicles and further protected by a mid level sheath called a perineurium. Further, multiple perineurium bundles of axons are typically nested within an outer sheath called an epineurium. Thus, each axon is protected by at least three sheath layers, i.e. an epineurium, a perineurium, and an endoneurium, going from outer most to innermost layer. Note that each large conduit or epineurium contains many bundles of endoneurium conduits, thus it would be possible to sever completely the axons of some nerve cells, while leaving intact the complete endoneurium of other nerve cells. [0009] The Seddon system is a basic classification system used to describe nerve injury where there are three categories of injuries - neuropraxia, axonotmesis, and neurotmesis. With neuropraxia, the integrity of the axon is preserved so the endoneurium, perineurium, and epineurium are all intact, but there is an interruption in conduction of the electrochemical impulse traveling down the axon. This is the mildest form of nerve injury.

Neuropraxia is typically a biochemical lesion caused by concussion injuries to the cell. There is a temporary loss of function, which is reversible within hours to months of the injury (the average is 6-8 weeks).

[0010] With axonotmesis, the integrity of the axon is interrupted but the endoneurium, perineurium, and epineurium are not punctured or deformed significantly. The result is typically loss of both motor and sensory functions, but with recovery through regeneration of the axon, a process that takes place at a certain rate per day, typically taking longer than neuropraxia for recovery. With neuropraxia and axonotmesis the intact endoneurium provides a guide for axonal regeneration where the nerve regenerates along the endoneural tubules. [0011] Conversely, with neurotmesis, the integrity of the supporting structures are disrupted or punctured, disrupting axonal regrowth and reimplantation. Typically, the injury results from severe contusion, stretch, or laceration of the cell or other internal disruption of the cell architecture sufficient to involve the perturbation of the endoneurium, perineurium, or epineurium. Results are typically complete loss of motor, sensory, and autonomic function. Thus, the electrochemical signals do not complete the connection to the muscle or target tissue. Neurotmesis injury is typically permanent.

[0012] Comparably, a temporary type of neurotmesis results from nerve toxicity caused by local anesthetic, which is typically injected in or near a nerve cell. Anesthetic also disrupts the electrochemical signals sent to the muscle, thereby causing a loss of motor, sensory, and autonomic function. Botulinum toxin or Botox®, as used with the popular cosmetic procedure for wrinkles, is used as a neuromodulator that works at the neuromuscular junction to block the transmission between the nerve and muscle resulting in paralysis of the muscle to reduce wrinkles. [0013] For these reasons, it would be desirable to provide a self-limiting medical heating device that offers both improved control over the location and amount of tissue heating and improved safety for both the patient and the operator. It would be further desirable to provide the ability to effect a wide range of cell injury from a minimum level of neuropraxia to full neurotmesis, through electrical current heating means, while causing minimum concurrent physical damage to other tissues in the target area. It would be still further desirable to provide temporary effects or permanent relief to a patient without surface tissue cosmetic defects. At least some of these objectives will be met by the invention, described below.

BRIEF SUMMARY OF THE INVENTION

[0014] In a first aspect of the present invention, a medical heating device is provided with an electrical resistance heater element formed out of a self-limiting conductive material. The self-limiting conductive material may be a conductive polymer or conductive ceramic material characterized by an electrical resistance that varies with temperature, such that heat production from electrical current through the material automatically varies with temperature preferably to control the temperature at or near a target control value. An enclosure, typically a thermally insulating jacket, contains at least a portion of the heater element which can be coupled, e.g., by wiring, to an electrical power supply which is usually also in the enclosure. A thermally conductive probe extends outward from the jacket or other enclosure and is thermally coupled to the electrical heater element. The medical heating device may be used in a method wherein an end or other exposed surface of the probe is touched to target tissue, whether for thermal ablation, denervation, cutting, or shrinking of the tissue or, if the probe is a hollow tube, for applying a heated material to the target tissue. Because the temperature of the probe is self-limiting due to the temperature-dependent resistance of the conductive material used for the heater element, the device has a "self-controlled" operating temperature and overheating and/or under heating of the target tissue is reduced or avoided.

[0015] In a second aspect of the present invention a radiofrequency or other high frequency electrical field is applied across target tissue, causing an electrical current to "conduct" across said target tissue. Heat is produced from this electrical current by ohmic or joule heating where the heat produced from such is proportional to the square of the amount of this current. A "lesion area" is created where tissue is heated above normal temperature. Heating occurs in a very controlled way where temperature of the lesion area does not rise above a maximum temperature. Carefully controlled heating provides the opportunity to cause a desired precise cell injury. Heat generation in the lesion area is controlled with a self-limiting conductive material electrical component in electrical series connection with the electrical current in the target tissue. The self-limiting conductive material electrical component precisely controls the electrical current flowing across the target tissue.

[0016] Heat production and temperature rise in tissue are directly proportional to the amount of high frequency current passing through the tissue, which is directly, where the duration and extent of the elevated temperature, along with location and size of the lesion area, primarily determine the type and extent of cell damage, which, in turn, determines whether the desired precise cell injuries are attained. Thus, this invention uses precise high frequency current control to yield a precise minimum level of cell injury required to effect the desired result for the patient without going beyond this level, thereby effecting the result without unnecessary cell injury.

[0017] The invention may be used in medical, dental, or veterinary applications.

Exemplary embodiments of the invention have cosmetic applications including treatment of wrinkles and remodeling of subcutaneous tissue. Exemplary embodiments are also used for therapeutic applications including treatment of muscle spasms and chronic pain and the control of one or more muscles of other target tissue. Exemplary embodiments are designed to specifically affect nerve tissue where the desired cell injury is to "deaden" the nerve or break the electrochemical connection, either temporarily or permanently, between nerve and muscle that causes nerve-to-muscle contractile function. However, this invention may be used to cause a desired precise cell injury to any type of cell or organ in the body within only the limitation of the relative sizes of the probes/needles on the invention apparatus as manufacturing technology changes with the times as compared to the size of the particular cells of interest, where cells may be of any type known human or otherwise. Other specific uses include cautery, i.e. stopping bleeding by the application of heat and treatment of migraines by deadening the trigeminal nerve. [0018] The present invention thus provides a high frequency alternating current medical device and method of using such. The medical device may be a handheld, battery-operated, low power, small electrical generator which can combine high frequency alternating current and direct current delivery with current controlled by a self-limiting conductive material. High frequency alternating current medical devices according to the present invention comprise a power source, an electric field generator, a self-limiting conductive material electrical component, at least one probe or needle-type projection, and at least two conductive segments located on said at least one probe or needle-type projection. The at least two conductive segments are electrically connected to said electric field generator so that an electric field is created between said conductive segments to operate in a bipolar manner. The electric field generator induces or generates an electrical current in said target tissue of an alternating current nature, which generates heat and causes a certain desired precise cell injury in a certain target tissue, such as nerve tissue. The electric field generator may also produce non-therapeutic pulses used to detect nerve cells by inducing the nerves to contract a muscle or display another observable response prior to therapeutic treatment. The desired precise cell injury may be neuropraxia to full neurotmesis thereby breaking the

electrochemical connection, either temporarily or permanently, between nerve and muscle that causes nerve-to-muscle contractile function. The self-limiting conductive material electrical component allows such precise cell injury with its placement in electrical series connection with said electrical current passing through said target tissue because said self- limiting conductive electrical component acts to control said electrical current in target tissue to prevent overheating of target tissue and does so through an inherent property of the self- limiting conductive material that varies its electrical conductivity with its temperature. The self-limiting conductive material electrical component behaves electrically like a thermistor, thermocouple, or switch. Self-limiting conductive material may be of a positive temperature coefficient (PTC) material, a negative temperature coefficient (NTC) material, a zero temperature coefficient (ZTC) material, or a combination thereof. High frequency alternating current medical device may be small enough to be handheld. The power source, electric field generator, self-limiting conductive material electrical component, at least one probe or needle-type projection, and at least two conductive segments may be incorporated into one device that is small and light enough to be comfortably held and very effectively handled by the surgeon to perform surgery.

[0019] Thus, in a specific aspect of the present invention, medical heating device comprises a hand-held enclosure which defines an interior which houses a power source, a portion of a heat conductive probe which extends from an end of the enclosure, typically the distal end, and which has a tissue-contacting distal tip, and a temperature change coefficient (TCC) element, typically a positive temperature coefficient (PTC) element or a combination negative temperature coefficient (NTC) and zero temperature coefficient (ZTC) element which provides a resistance change, usually an increase when employing a PTC, in the range from two to four orders of magnitude in response to a temperature change in the range from 20 C° to about 100 C°, typically from 30 C° to about 80 C°, although larger temperature changes can be employed in some applications. That is, the resistance value measured in ohms will usually increase (or in other cases be reduced) by from two to four orders of magnitude when the temperature of the TTC material changes by a magnitude within these temperature ranges. Passing current through the TTC element causes the temperature of the material to rise, and the heat conductive probe is coupled to the TTC element to conduct heat from the TTC element to the tissue contacting distal end of the heat conductive probe. In this way, the distal tip of the probe can be contacted against tissue to deliver heat generated in the TTC element. As the heat is conducted down the probe, the temperature of the TTC material will be cooled, thus resulting in a lowering of the resistance in a PTC material. When the resistance lowers, the current flow through the PTC will increase, thus restoring the temperature toward the inflection point in the PTC curve (fig. 8), as discussed below in this application. [0020] The medical heating devices will preferably comprise a PTC element having particular composition as described herein below. The exemplary power supply will be a direct current battery, and an exemplary enclosure will comprise a thermally insolating jacket. The PTC element may take a variety of forms. For example, the PTC element may be in the form of at least one coil wound around a core electrical spacer wherein the electrical core spacer functions to electrically separate some areas of the PTC element while electrically connecting other areas of said PTC element to said electrical power supply to yield an electrical current path through the length of the coil. Alternatively, the PTC element may be in the form of a sheet wrapped around a core electrical spacer where opposite ends of the sheet are connected to the electrical power supply to provide an electrical current path through the entire sheet. Thirdly, the PTC element may be in the form of an elongated coil with longitudinal channels running therethrough or thereover to connect the PTC element to the power supply. The heat conductive probes may take a variety of forms, typically being needle-shaped probes, optionally being hollow tubes having any one of a variety of circular shapes. Alternatively, the probes could have non-traumatic distal tips which are rounded, roller-balled, blunt, or the like.

[0021] The medical heating device as just described may be used to deliver heat to a tissue location. The current is passed from the power source through the TCC or PTC element so that the TTC or PTC element heats. The tissue contacting distal end of the heat conductive probe is engaged against the target tissue location, and heat is delivered to the tissue. As described above, the delivery of heat causes the probe to cool which in turn causes a PTC element to cool, lower its resistance. As the resistance lowers, the current flow will increase, thus generating more heat and restoring the PTC element to the inflection point.

[0022] In a further aspect of the present invention, a high frequency medical heating device comprises a hand-held enclosure having an interior cavity suitable for holding various device components. A power source and an electric field generator are both housed within the enclosure. The electrical field generator draws current from the power source, typically a battery, and generates a radiofrequency (RF) or other high frequency current. At least one tissue probe is coupled to the hand-held enclosure and has two conductive segments thereon (or optionally one conductive segment on two or more tissue probes) where the conductive segments are adapted to engage and deliver RF energy to tissue. A temperature change coefficient (TCC) material, preferably a positive temperature coefficient (PTC) element, similar to the one described above, is also disposed within the hand-held enclosure and connected between the electric field generator and the power source. As the electric field generator delivers more energy to the conductive segments, the current flow through a PTC element will increase, thus causing it to heat and increase in temperature. The increase in temperature will reduce the current delivered to the electric field generator, reducing the current flow and controlling the current to a desired target level.

[0023] In a preferred aspect of this embodiment, the tissue probe may be provided on assemblies which are removably or detachably connected to the enclosure so that different tissue probes may be interchangeably attached to the enclosure. For example, tissue probe assemblies having a single tissue probe, a pair of tissue probes, or three tissue probes may be provided so that they may be interchangeably connected to the hand-held enclosure. In some cases, the tissue probes may be tissue penetrating for treatment. In other cases, the tissue probes may be non-tissue penetrating, particularly when the hand-held device is used for nerve stimulation. In such cases, the electric field generator will be adapted to selectably deliver either the radio frequency energy or to deliver direct current energy of a type and magnitude, typically direct current, which will stimulate nerves when the tissue probes are engaged against the patient's skin. This is particularly advantageous for locating nerves which may then be treated with the RF energy after the probe assembly is exchanged for a tissue-penetrating probe assembly.

BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Fig. 1 A is a perspective view of an exemplary hand piece which includes self- limiting electrical heating element, insulating jacket, cutting probe, and circuit connection to the power source. Figs. IB and 1C are perspective views of alternative forms of hand piece in accord with the present invention.

[0025] Figs. 2A and 3 A are partially cut-away perspective views of a probe distal end of first and second embodiments of medical heating device respectively, illustrating two different heating element arrangements. Figs. 2B and 3B are cross-sectional views of Figs. 2 A and 3 A.

[0026] Figs. 4 and 5 are partially cut-away perspective views of a probe distal end of third and fourth embodiments of medical heating devices respectively, illustrating the addition of a replaceable probe module in Fig. 4 and an optional sensor in Fig. 5. Fig. 5 A is a cross- sectional view of Fig. 5.

[0027] Fig. 6 is a circuit diagram of medical heating device.

[0028] Fig. 7 is a logarithmic graph of electrical resistance (ohms) versus temperature (C) for a preferred PTC self-limiting electrical heating element. [0029] Fig. 8 is a logarithmic graph of electrical resistance (ohms) versus temperature (C) for a PTC self-limiting electrical heating element compared with that of an on/off switch.

[0030] Figs. 9A, 9B, 9C, and 9D depict logarithmic graphs of electrical resistance (ohms) versus temperature (C) of a NTC, a ZTC, a NTC/ZTC blend material, and a PTC/ZTC blend material. [0031] Fig. 10 is a logarithmic graph of electrical resistance (relative to resistance at 25°C) versus temperature (C) for various conductive polymer base materials with different polymer softening points, for use in selecting an appropriate conductive polymer material for a specified tissue ablation or tissue cutting application.

[0032] Fig. 1 1 is a circuit diagram of a basic mode of medical device with two probes or needle-type projections.

[0033] Fig. 1 1 A is a circuit diagram of a basic mode of medical device with one probe or needle type projection.

[0034] Fig. 12 is a circuit diagram of an exemplary medical device constructed in accordance with the principles of the present invention. [0035] Fig. 13 shows perspective views of an exemplary medical device with a replaceable tip attached and removed, with blow-up views of each. Fig. 13A shows an alternative replaceable tip with non-penetrating electrodes intended to nerve stimulation on the surface of the skin.

[0036] Fig. 14A is a cross-section of the medical device. Fig. 14A. [0037] Fig. 14B is top plan view of medical device. Fig. 14B also defines cross-sectional plane 14 A.

[0038] Fig. 14C is a cut-away view of Fig. 14B.

[0039] Fig. 15 is a blow-up of a side elevation view of the distal end of medical device. [0040] Fig. 16 is a blow-up of a top plan view of the distal end of medical device.

DETAILED DESCRIPTION OF THE INVENTION

[0041] The present invention provides a medical device and method of using such.

Medical devices according to the present invention comprise at least one probe or needle-type projection at its distal end and at least two conductive segments located on said at least one probe or needle-type projection. At least one probe or needle-type projection is capable being inserted into a body cavity or into body tissue, at which point also capable of conducting electrical current between said at least two conductive segments. In "one-probe or needle-type projection" mode, said at least two conductive segments are located on the one and only probe or needle-type projection. In "two-probe or needle-type projection" mode, one of said at least two conductive segments is typically located on each of the two probes or needle-type projections. Probes or needle-type projections are typically inserted into tissue or a body cavity containing the target cells or into nearby to such; then an electrical current is conducted between said segments to effect the desired precise cell injury. Probes or needle- type projections may be inserted into tissue, so that electrical current occurs subcutaneously. In this fashion, the heat-defined lesion area is entirely subcutaneous, resulting in minimal change of appearance on the surface of the tissue. The medical devices further comprise a power source capable of applying a therapeutically or diagnostically effective electrical fields across said at least two conductive segments in order to generate the appropriate electrical current in the target tissue. The power source may be alternating current and/or direct current.

[0042] In particular embodiments, the medical devices further comprise an electric field generator capable of being powered by said power source and generating one or more electric fields across said at least two conductive segments. Preferably, electric field generator is small and miniaturized. Electric fields may be generated in continuous wave form, such as sine, triangular, or square wave or similar, and at various frequencies, intensities, and polarizations in order to yield a desired heating to cause the desired precise cell injury.

Alternatively, the electric fields may have of a direct current pulse nature, as well, such as sine, triangular, or square wave or similar pulse shape. Electric field generator may emit several different shaped pulses and continuous wave forms at the same time. An exemplary electric field generator may be small enough to be handheld but also capable of supplying a three-watt field into 150 ohms at 460KHz using a hand-held direct current battery power source, although more or less power may be delivered depending on battery strength and other conditions.

[0043] The medical devices of the present invention further comprise a self-limiting conductive material electrical component in electrical series connection with said electrical current passing through the target tissue. "Self-limiting conductive material" is defined as a material whose electrical resistive properties vary with its temperature. Self-limiting conductive material electrical component functions electrically like a thermistor, a thermocouple, or a switch in the electrical heating circuit of the target tissue. Self-limiting conductor material electrical component, in effect, controls the electrical current passing through the target tissue, and thus controls the temperature of the target tissue, and tissue surrounding target tissue. In particular, as described below, a preferred self-limiting conductive material is provided which has the temperature response curve of a thermister which is advantageously used in the devices of the present invention.

[0044] The entire medical device may be small enough to be handheld. The power source, electric field generator, self-limiting conductive material electrical component, at least one probe or needle-type projection, and at least two conductive segments may be incorporated into one device (within a common enclosure), small and light enough to be comfortably held and very effectively handled by the surgeon to perform surgery.

[0045] The medical heating device 10 (Figs. 1-5) comprises: a self- limiting electrical heating element 20 electrically coupled to a power source 30 (Fig. 6) by an electrical wire circuit connection 40. Medical heating device 10 further comprises: a thermally insulating jacket 50, a thermally conductive probe 60, and a core electrical spacer 70, as discussed below.

[0046] The self-limiting electrical heating element 20 behaves electrically like a standard electrical heating element in serial connection with a thermistor. Thus, in Fig. 6, the self- limiting electrical heating element 20 is represented by an electrical heating element symbol 26 in serial connection with a thermistor symbol 23. The thermistor property, in effect, regulates electrical current through the electrical heating element property. In reality, the self-limiting electrical heating element 20 is one electrical component, consisting essentially of a homogeneous blend of different materials, including a base material and a conductor dopant, as described in more detail below.

[0047] The self-limiting electrical heating element 20 behaves like an electrical heating element 26 because the heat it produces results primarily from electron, ion, or other charged- particle collisions occurring inside of the heating element. Such heat causing collisions are induced by an electric field across the heating element resulting from an electrical wire circuit connection 40 through the heating element to an electrical power supply 30 with voltage V and current I. See Fig. 6. This phenomenon is known as ohmic heating, joule heating, or resistive heating. As with ohmic heating, the amount of heat Q produced from this invention is proportional to the square of the electrical current passing through the self-limiting electrical heating element 20, i.e. Q « I².

[0048] The self-limiting electrical heating element 20 behaves like a thermistor 23 because its electrical resistance R varies as a function of temperature T, which is the definition of a thermistor. Since this relationship is typically nonlinear, we use log scales of resistivity are used to illustrate its relationship with temperature (Figs. 7-10). If resistance increases with increasing temperature, the device is called a positive temperature coefficient (PTC) thermistor or posistor. If resistance decreases with increasing temperature, the device is called a negative temperature coefficient (NTC) thermistor. Resistors are designed to have constant resistance over a wide temperature range and are sometimes called zero temperature coefficient (ZTC) materials, which could be another subset of thermistor. Collectively, the PTC, NTC, and ZTC materials are referred to as temperature change coefficient (TCC) materials herein.

[0049] The properties of ohmic heating and temperature responsive resistance together regulate the temperature of the self-limiting electrical heating element 20. Changes in the temperature of the medical cutting device, caused by using the device cause changes in resistance. Resistance is inversely proportional to current, i.e. R ~ Γ¹. As stated above, heat

2 2

produced is proportional to I , thus, Q ~1 R^" . Therefore, small changes in resistance yield relatively large changes in heat production from the self-limiting electrical heating element 20. There is a maximum R, however, where resistance becomes too large to allow an electrical circuit connection between the power source and the heater element aspect of 20. Above this temperature, the heater is shut off, resulting in rapid cooling.

[0050] In a specific and preferred embodiment, the self-limiting electrical heating element 20 is made of PTC material. Fig. 7 is a graph of the electrical resistivity versus temperature of a PTC heater material suitable for use in the present invention. Suitable methods have a resistivity that gradually increases with temperature as noted by the mid-level positive slope character of the graph (between TL and TH. Further, there is an inflection point in the graph at To. AS temperature rises above To_, resistivity increases at a decreasing rate with temperature. Thus, there is a gentle heat production decrease at a decreasing rate as temperature rises above To. As temperature falls below To_, resistivity decreases at a decreasing rate with temperature. Thus, there is a gentle increase in heat production at a decreasing rate as temperature falls below To. With reference to Fig. 7, going from To to TH, resistivity gradually increases, thereby decreasing heat production, thereby cooling the heater element back to To. Likewise, going from To to T_L, resistivity gradually decreases, thereby increasing heat production, thereby heating up the heater element back to To. There is a mathematically stable temperature point at To, otherwise known as an inflection point.

Materials with this inflection point relationship yield optimum characteristics for the present invention having an optimal stability to keep the device steadily set at To. Thus, PTC heaters are capable of "automatic temperature control" or an inherently stable temperature To when it is placed in an electric field strong enough to induce heat-producing current. Furthermore, the steady state temperature remains at To across a wide range and fluctuation of voltages from direct current or alternating current power supplies 30.

[0051] Any standard electrical heating element combined with a "thermostat switch" or thermocouple can provide an "on-off ' control with temperature oscillation around T₀. Such on-off control, however, requires an offset "hysteresis" between the on and off temperatures, TL and TH, resulting in significant temperature fluctuations around To. The self-limiting electrical heating element 20 in contrast, provides a more stable control with less fluctuation. See Fig. 8 where To is 75° C. With a switch, the heater is either on fully on or off completely. As a result, the heater continuously cycles from extreme high heat production to zero heat production while zeroing in on target temperature To. On the other hand, with this invention, electrical resistance only gradually changes with temperature, thereby only gradually changing heat production while minimizing oscillations around target temperature To.

[0052] Below the transition temperature To, the composition used for the switch has a very low resistance, on the order of 10 ohms or less. Thus, an on-off switch turns the heater on fully at temperature just below To. On the other hand, the exemplary self-limiting electrical heating element 20 of the present invention, only drops to about 1000 ohms, thereby causing only a slight increase in heat production at the same temperature. Above the transition temperature, a switch will have a very high resistance, on the order of 10⁹ ohms or higher. Thus the switch turns the heater completely off. In contrast, the self-limiting electrical heating element composition of the present invention has only a slightly higher resistance at this temperature, thus heat output only slight decreases. Moreover, with medical heating devices, this temperature fluctuation is exacerbated as the device may incur a large heat sink while in full contact with tissue at one instant and an instant later incur no heat sink with the device at rest only in contact with air. The thermistor-type heating element 20 of the present invention thus yields a medical heating device with a much more constant target temperature as compared to prior art medical heating devices controlled by on-off temperature switch, even while allow for rapid fluctuation of heat sink activity associated with tissue ablation of cutting.

[0053] The inflection point relationship between resistivity and temperature of PTC material is further preferred because it results in a self-limiting electrical heating element 20 with a relatively small temperature deviation around To of only a few degrees, e.g. 3-10 degrees centigrade. Thus if TH and TL were the respective maximum and minimum temperatures of the heater system when subjected to medical use, the control range (TH - TL) would be much less for the self-limiting electrical heating element(s) as compared to the switch operated medical heating device element. Exemplary heating elements 20 will typically provide a temperature control range of about 3° C to 5° C, material used as the thermistor in the medical heating device. [0054] Different tissue ablation or cutting procedures may require different optimal temperature operating ranges. For instance, different procedures may require different shaped and sized cutting probes, thereby changing heat sink requirements, thereby changing the heat production and temperature ranges of the medical heating device. Different target tissues are ablated in different procedures, which may require different optimal cutting temperature ranges of the medical heating device for each procedure. Thus, certain tissue ablation or cutting procedures may require different target temperatures To with different operating ranges TH to TL. These criteria may be adjusted by carefully choosing a PTC, NTC, or ZTC heater material for the self-limiting electrical heating element 20 with the best resistance temperature graph. Further, various dopants and various concentration of dopants may be used to vary characteristics to yield different resistance temperature graphs. Further combinations of PTC, NTC, and ZTC materials may be used to yield different resistance temperature graphs. Many of these materials are currently commercially available.

[0055] Fig. 9A includes the resistance temperature relationship of a NTC material. This arrangement may be used to create an operating temperature To with sharp cut-off at such temperature. Fig. 9B includes the resistance temperature relationship of a ZTC material. This arrangement may be used to create a constant heat output at a certain level across a wide range of temperatures TH to TL. Fig. 9C includes the resistance temperature relationship of a NTC/ZTC blend material. This arrangement may be used to create a wide operating temperature range of TH to TL with constant heat output at a certain level but with sharp cutoff at temperature T_L. Fig. 9D includes the resistance temperature relationship of a PTC/ZTC blend material. This arrangement may be used to create a wide operating temperature range of TH to TL with constant heat output at a certain level but with sharp increase in heat production at temperature TL thereby preventing the probe temperature from ever falling below TL.

[0056] PTC, NTC, and ZTC materials can be made from a crystalline or semi-crystalline polymer base material with certain conductive "doping" material added. With polymer based thermistors, transition temperature results from the melting or freezing of polymer molecules. With crystalline or semi-crystalline polymers, molecular structure is more tightly packed in solid phase and less tightly packed in liquid phase. Polymer molecules are generally non- conductive, so a conductive dopant must be added to make the material conductive. At temperatures below To, most polymer molecules are in solid phase, thus closely packed, thus at their most conductive state or level. At temperatures above To, most polymer molecules are in liquid phase, thus loosely packed, thus at their least conductive state or level. For the same choice of a matrix polymer, transition temperatures To generally coincide with the polymer softening point of the selected matrix polymer. In Fig. 6, both switch and heater are made from the same type of polymer material, thus they have the same transition temperature To.

[0057] Materials having these properties are known and commercially available with a range of transition temperatures To. Fig. 10 illustrates different transition temperatures for a number of possible polymer matrices for a conductive polymer composition. Thus, successively increasing transition temperatures are seen for conductive polymers made using matrices of polyvinyl sterate, polycaprolactone (PCL), ethylene ethylacrylate (EEA), low- density polyethylene (LDPE), high-density polyethylene (HDPE), polypropylene (PP), polyvinylidenefluoride (PVF2), polyvinylfloride (PVF), ethylene tetrafluoroehylene copolymer (ETFE), ethylene perfluoroalkoxy copolymers (PFA),

tetrafluoroethylene/hexafluoropropylene copolymer (FEP), etc. Table I shows crystalline melting points for several polymers. Conductive polymer compositions usable with the present invention may include any of these polymers as well as those described in U.S. Patent Nos. 4,514,620 and 5,554,679, the full disclosures of which are incorporated herein by reference. PTC, NTC, and ZTC materials can also be made from blending two or more conductive polymers.

TABLE I

Polyethyleneterephthalate (PET) 250-265

Ethylene-Tetrafluoroethylene copolymer (ETFE) 270-271

Perfluoroalkoxy copolymer (PFA) 250-305

Fluoroethylene-propylene copolymer (FEP) 290-291

Polytetrafluoroethylene (PTFE) 325-327

[0058] Dopant material is added to base material in order to render it conductive which allows the material to perform like a heating element. Also dopant is added to slow the resistance change or to widen the graph discussed above. Dopants are conductive material such as carbon black, metal oxide, semi-conductor material, blends thereof, or other material that is conductive and capable of being produced in small particles. The specific resistivity temperature relationships of PTC, NTC, and ZTC materials are arrived at by varying the type and concentration of dopant. For instance, the switch in Fig. 8 has the same type of dopant as the self-limiting electrical heating element but the self-limiting heating element has a much smaller and evenly dispersed concentration of the dopant. Thus, a lower concentration or density of conductive particles in the polymer base composition is one way to obtain the desired gradual change in resistance for a self-limiting heater element. Generally speaking, dopant levels above 50 percent yield switch type material, dopant levels of 15-40% yield thermistor material, and dopant levels of 10% yield electro magnetic interference and or electrostatic discharge. Also, porosity, surface area, particle size, and oxygen content, of the conductive dopant may be varied to produce various properties. Also, more than one type of dopant may be added to base material. Either the base material molecules or the dopant material particles may actually cause the ohmic heating. Thus, dopant may function to produce electron transfer or vibrational heating or both. All of these factors together with various carbon black loading levels and others results in a near endless amount of combinations between type(s) and amount(s) of dopant along with type(s) of base material to yield a near endless amount of specific resistivity temperature relationships.

[0059] PTC, NTC, and ZTC materials can also be made from a ceramic material or ceramic based material with conductive dopant added. Ceramic material can be conductive or not conductive depending on phase. Ceramic material can be engineered to change phase from solid to liquid or liquid to solid at specific temperatures T₀. Typically, ceramic base material is barium titanate and/or related divalent titanates and zirconates. Typical dopants include lead, strontium, rare earth metals, antimony, bismuth, or similar. Dopants are added to increase or decrease the anomaly range of the base material or further adjust the slope of the resistivity temperature relationship. Various ceramic thermistor heaters with different temperature resistivity relationships are commercially available. Also, a ceramic thermistor heater material manufacturer may endeavor to undertake special development programs to deliver specially desired characteristics. [0060] Typically, the particular self-limiting electrical heating element 20 is selected based upon the requirements of the medical procedure and in particular the desired operating temperature range for the particular tissue ablation to be performed. A suitable self-limiting electrical heating element material, whether PTC, NTC, ZTC or combination thereof, can be selected to yield this temperature range. Note that size, shape, and conductivity of both probe and insulating material and other factors influence the operating temperature range of the probe and heater. All influential aspects are factored into a calculation performed to yield the desired resistance temperature graph. Then the best commercially available thermistor material is chosen with the best resistance temperature graph to fit the specific medical procedure desired. [0061] The physical form of a suitable self-limiting electrical heating element 20 may comprise or consist of one or more rings or loops 22 of the PTC/NTC/ZTC material that are wound around a core electrical spacer 70. See Fig. 2A. The core electrical spacer 70 keeps a pair of circuit connection wires 40 spaced apart to prevent an electrical short. Individual loops 22 of heating element 20 can be connected in parallel to electrical wire circuit connection wires 40 to provide a set of electrical current paths through loops 22.

Alternatively, the two end loops 22 of heating element 20 could be connected to wires 40 to yield a current path along the entire length of heater 20.

[0062] As seen in Fig. 2B, the core electrical spacer 70 has a cross-section with grooves or channels that accommodates lengthwise passage of the wires 40 as well as one or more thermally conductive probes 60 or possibly also a sensor (not shown here). In particular, core electrical spacer 70 may have a set of lengthwise indentations 73 having shapes that closely match the respective wire 40, probe 60 or sensor components that are received therein.

[0063] Self-limiting electrical heating element 20 may alternately consist of a sheet form 24 of PTC/NTC/ZTC material wrapped as a blanket around core electrical spacer 70 (Figs. 3A and 3B). Sheet 24 is connected along the length wire electrodes 40 in a manner that provides parallel electrical current paths through the entire sheet 24. Another possible arrangement would be to simply have one wire 40 contact the sheet 24 at the distal end and the other wire 40 contact the sheet at the proximate end. [0064] Yet another alternative would be to employ a core electrical spacer 70 that is itself made from the self-limiting conductive PTC/NTC/ZTC material. As wires 40 extend through the entire length of core spacer 70, current would flow in parallel through the bulk of the spacer material to produce heat. A number of commercially available self-regulating heater cables, marketed for use as storage tank heaters, ground heaters, in pipe freeze protection or for domestic hot water temperature maintenance, have such a construction, such as those manufactured by Tyco Thermal Controls, LLC under their Raychem brand. In such a construction, probe 60 would need to be electrically insulated from the conductive spacer material 70, e.g., by having an electrically insulating cladding. [0065] In addition to core electrical spacer 70 there may be another electrical spacer called a rim electrical spacer 75 in the embodiments of Figs. 2A/B and 3A/B. Rim spacer 75 is an electrical insulator in some areas and thermally conductive in other areas. Electrical insulating material would be required between all portions of self-limiting heater 20 and circuit connection wires 40 where conductivity is not desired. This pattern would be different for a serial heater connection as compared to a parallel heater connection. For instance, in Fig 3 A, there would be a longitudinal slit down the full length of rim spacer 75 to provide parallel loop connection discussed above. Also, rim electrical spacer 75 would be required to be thermally conductive in other areas, e.g. near the probe so that heat may freely transfer from heater 20 to probe 60 between rim spacer 75. [0066] A thermally insulating jacket 50 (Figs. 2A/B and 3A/B) can provide at least a portion of the exterior surface of the hand-piece or handle. Jacket 50 functions to insulate the heat produced by heating element 20 to keep heat inside the device and provide a non-heated handle for the user to easily control the tissue ablation device. Although not depicted in drawings, jacket 50 usually extends all the way down to cover core electrical spacer 70. In Fig. 1 A, thermally insulating jacket 50 has exterior shape similar to a pen. This shape is believed to deliver superior control and feel of the device as a scalpel-type device. Fig. IB illustrates a jacket 50 having a thicker handle much like handles found on a screwdriver. Jacket 50 may take whatever exterior form that proves most desirable for the user.

[0067] The thermally insulating jacket 50 will usually cover all electronic circuitry in the hand piece. The jacket 50 is preferably made from a high resistance material with an electrical resistivity on the order of log 10¹⁰ ohm-cm or higher in order to contain electrical fields created by the circuitry. Thus, the medical device 10 will preferably not produce any electromagnetic interference or electro-static discharge. [0068] The thermally conductive probe 60 (Figs. 2A/B and 3A/B extends outward from the thermally insulating jacket 50 and is thermally coupled to self-limiting electrical heating element 20. Probe 60 may have any of several shapes, including a circular cross-section 62, a square cross-section 64, an oval, rectangular or other oblong cross-section, a rounded tip 66, or perhaps one with a roller-ball tip, a blunt tip, a pointed or other piercing tip as 68, and may even form a hollow tube adapted to supply a fluid that has heated by the device for application onto or injection into target tissue. The probe could also have more than one needle or be multi-pronged as in fork-like probe. Likewise, the probe may be accompanied by or may include cutting, suturing or stapling capabilities, and thus may form any of several known manipulable medical tools, such as those used in arthroscopic surgery, provided it is thermally conductive to receive and transmit heat from the device's heater element. For example, the probe tip may include a tool for delivering preheated biodegradable staples or other material to target tissue. The preheated material delivered by such a tool could be used to cauterize blood vessels or ablate nerves or other tissue. [0069] Probe 60 may be part of an interchangeable module with a probe support 61 (Fig. 4) that is attached to self-limiting electrical heating element 20, thermally insulating jacket 50, or electrical spacer 70 with pins, screws, ratchets, spring detents, magnets, connectors, or other attachment means. Fig. 4 depicts pins 63 attachable to core 70. In any event, probe support 61 reversibly connects to the medical heating device where a variety of probes types are also fitted with the same support 61. Support 61 provides ability to quickly snap on and off different probes in order to more effectively perform a medical procedure.

Interchangeability of probes offers much greater flexibility in a particular heating device's usefulness. Provided the heating requirements are similar, different medical applications can be performed using the same tool simply by swapping one probe module for another. [0070] Probe 60 may include or support at least one sensor 66, which can be an imaging device, such as a fiber-optic imager, positioned relative to the probe 60 and that can be coupled through the plug assembly to a suitable display so as to aid a user in directing the probe to a target location. Any such imaging sensor or scope may be equipped with an antifogging device or agent. Heat from self-limiting electrical heating element 20 may be used with such antifogging device or agent. Sensor 66 could also be a nerve detector. Such nerve detectors are known and used in other probe-like medical tools. Like the imager, they too can be suitably located near the probe 60, or may even be integrated into the heated probe itself for finer control over positioning. [0071] Electrical wire circuit connection 40 creates a circuit connection between self- limiting electrical heating element 20 and electrical power supply 30. Electrical may be standard 1 lOVAC, AC battery, DC battery, solar cell, or custom power source module that is itself power by any of the preceding. An exemplary power source 30 (Fig. 1 A), typically includes the circuitry to deliver RF of other power to the device 10 as well as form receiving signals from the sensors 66. The power source 30 is connected by a cable 40 and removable plug 45. With Fig. 1 C, the power source and electrical wire circuit connections are completely contained inside of thermally insulating jacket 50. Thus, medical heating device 10 has "a wireless mode" as depicted in Fig. 1C (i.e., is free from external wired connectors). [0072] Medical heating device 0 may further comprise on/off switch 80 which may be located on thermally insulating jacket 50, close to the user's hand when the device is in operation (Figs. 1A-1C). On/off switch switches on and off electrical circuit connection 40 from power supply 30, thereby shutting off power to self-limiting heater 20.

[0073] Medical heating device 10 may be used in conjunction with other medical devices such as ultrasonic, mono-polar electro surgery, bi-polar electro surgery, suction, inflation, insufflation, microelectronic chip, fiber optic, radio frequency, microwave, infrared, X-ray, lasers, light emitting diode, resistance or wire heating, or other standard medical device capable of being installed on or near probe 60. Electrosurgery is the application of a high- frequency electric current to biological tissue as a means to cut, coagulate, desiccate, or fulgurate tissue. In electrosurgical procedures, the tissue is heated by an electric current through itself. Its benefits include the ability to make precise cuts with limited blood loss. Electrosurgical devices are frequently used during surgical operations helping to prevent blood loss in hospital operating rooms or in outpatient procedures.

[0074] The medical heating device 10 constructed according to the present invention may be used by touching the distal end of probe 60 (e.g., sensor 66) to target tissue, whether on the skin surface of a patient, subcutaneously or deeper. If the target tissue is skin, the maintenance temperature of the device could be chosen to be not more than 45° C (113°F). At such a moderate temperature the heat transfer from the probe to the skin can produce skin tightening, skin resurfacing and collagen remodeling, for dermal regeneration and cosmetic applications. This can also be accompanied by mechanical ablation of skin surface cells. Alternatively, a higher temperature could be used to cut skin, while simultaneously cauterizing any bleeding. [0075] If the target tissue is subcutaneous adipose (fat) tissue, heat transfer through a piercing probe inserted into the skin can be used to cause selective damage to fat cells proximate to the probe end. If the target tissue is nerve tissue, heat transfer from the probe can be used to ablate a selected nerve, such as a trigeminal nerve (e.g. for the treatment of migraines), a rami of the temporal branch of the facial nerve or angular nerve that supplies innervations to the corrugator and procerus muscles of the face. This can aid in removing frown lines.

[0076] The target tissue might be glandular, as in sweat glands of the skin to treat hyperhidrosis or the tonsils in the oral cavity in performing a total or partial tonsillectomy. [0077] The target tissue could be vascular (veins, arteries, capillaries, blood), wherein heat transfer through the probe can be used to produce local blood coagulation and cauterization of the vascular tissue. Or, at more gentle temperatures (near 37° C body temperature), a hollow probe can inject a pre-heated fluid into the target artery or vein, e.g., for localized drug delivery. [0078] The target tissue could be some abnormal growth, polyp or tumor, such as in the sinus or oral cavity. Here, heat transfer through the probe can ablate that tissue. Examples include: mucosal lesions found in Barrett's esophagitis, or tissue growth from nasal turbinate hypertrophy, or removal of colon or rectal polyps.

[0079] A heated medical device could also be used as part of a pain management or treatment protocol by applying heat to selected nerve or muscle tissue, e.g., to ablate sensory nerves or to stimulate blood flow in sore muscles.

[0080] A medical device constructed with a self-limiting electrical heater element in accord with the present invention can replace the present electrical-arc-based devices used for similar purposes. Any medical application requiring controlled heat delivery to selected target tissue can employ the present invention with much greater control and safety. The invention may be used in medical, dental, and veterinary procedures.

[0081] A presently preferred material for the self-limiting electrical heater is a combination of one or more NTC material(s) and one or more ZTC material(s) with a resistance vs.

temperature response curve similar to that shown in Fig. 9C. Suitable materials include NTC thermistor 3, MF51 , MF52, and CWF from Cantherm, Montreal, Canada, and various materials from General Electric, Fairfield, Connecticut, USA. [0082] Referring to Figs. 11-18, a power source 97 which generates an electric field between a set of at least two conductive segments (conductive segments) 225. The power source 97 may directly generate the electric field between conductive segments 225 or alternatively may indirectly power an electric field generator 100, which in turn generates the electric field between conductive segments 225. The power source 97 may be a direct current or an alternating current power source. In the case of a direct current power source 97, the electric field generator 100 would be required to produce alternating current or alternating polarity electric fields in the target tissue 250. An exemplary power source 97 is a direct current battery because there are many standard sizes of such batteries that are small in size but also capable of powering a special electric field generator device capable of producing the appropriate electric fields resulting in the desired precise cell injury.

[0083] Alternating current, as opposed to direct current, is preferred because alternating current can produce more heat per amp than direct current in this situation. There appears to be a particular resonance frequency or spike frequency where heat production is maximized from alternating current travelling across a particular type of target tissue 250. At this frequency, current passes through the target tissue 250 with the least resistance. Thus, at a particular resonance frequency of a particular target cell, less power is required to produce the same or more heat in that cell. Thus, alternating current is preferred because it reduces the power requirements of the device, and thereby allows the device to be small enough to be hand-held. The resonance frequency of nerve cells and their surrounding tissue is 460KHz and thus is the preferred frequency. Electrosurgical devices commonly operate at this frequency because this frequency appears to be the resonance frequency of many types of tissue, not just nerve tissue.

[0084] Electric field generator 100 comprises a pulse width modulation power supply electrically connected to common circuit board components including resistors, capacitors, diodes, and switches. Electric field generator 100 may further comprise a transformer 175 (Fig. 12), where the output signals from said pulse width modulation power supply are the primary connections with said transformer. Electric field generator 100 is typically custom designed to generate a specific alternating polarity field, with a specific frequency and power, in order to function properly with the specific probe/extension 200 of device 91 according to the requirements to yield the specific desired precise cell injury. Exemplary electric field generator 100 produces an output appropriate for nerve cells using a three-needle probe 200 where the generator was also designed to be of a very small size. Electric field generator 100 includes pulse width modulation power supply and circuit board components assembled onto a custom circuit board, having an overall long and narrow shape such as rectangle, that is capable of fitting inside of an enclosure of the shape and size of a typical pen as depicted on Figs. 14-16. Alternately, electric field generator 100 may consist of many electrical circuit boards that are electrically connected by loose wires to fit inside of various differently shaped enclosures. Electric field generator 100 includes a doughnut shaped transformer 175 electrically connected to the distal end of said custom circuit board with the distal end inside the doughnut hole of transformer 175, where the secondary voltage and current from transformer 175 is passed through the target tissue 250.

[0085] The mode pulse width modulation power supply comprises at least six electrical connections: two power input connections consisting of positive and negative power connections 101 and 103; two signal output connections 105 and 107; and two trimmer input connections 109 and 111. Output signals 105 and 107 create electric fields in the target tissue located between conductive segments 225 in rapidly changing alternating polarity in order to generate or induce the alternating current in the target tissue. Current is generated or induced because tissue contains water and other conductive molecules to allow electrical current to take place in response to the electric fields. Output signals 105 and 107 are electrically processed through said custom circuit board before electrically connecting with conductive segments 225. The frequency of the alternating polarity of the electric fields largely matches that of the frequency of the alternating currents created thereby. Alternately, outputs 105 and 107 may be electrically connected to the primary inputs on transformer 175, where secondary outputs of transformer 175 are 105a and 107a. Transformer 175 can be used to help stabilize resonance frequency on the target tissue, filter out switching noise from generator 100, and extend battery life of device 91 by operating generator 100 at more efficient frequency than resonance 460KHz pertaining to nerve tissue. Further, electrically processed signal from 105, 105a, 107, or 107a may be looped back to a control unit 125, as discussed below, where signals are further processed and returned back to inputs 109 and 1 11 on electric field generator 100.

[0086] The electric field generator 100 is preferably capable of emitting one or more direct current pulses from signal output(s) 105 or 107 into target tissue 250 in order to detect the target nerve and provide a precise location of high frequency alternating current medical device prior to heat production. Before the surgeon delivering the alternating current field that heats target tissue 250, the surgeon can locate the precise target nerve cell or component thereof using the one or more direct current pulses. Direct current pulses may be of various amplitudes and wave forms, and optionally, multiple shaped pulses may be emitted from the electric field generator 100 at the same time. By positioning the at least two conductive segments on or into the area of the target cell, pulse(s) emitted from conductive segments stimulates the muscle that the nerve drives, thereby causing said muscle to twitch or move in some way. Thus, by moving the probe 200 and conductive segments 225, the target nerve can be located before delivering the treatment current which dernervates the nerve.

Searching occurs until the sought after muscle twitches or otherwise the correct movement is witnessed, at which point the surgeon knows the correct nerve cell or component thereof has been located and that the at least two conductive segments are now precisely located on the exact target tissue 250. Thus, high frequency alternating current medical device 91 can be very precise and accurately positioned because the at least two conductive segments are known to be exactly located correctly by detecting and identifying the precise location of high frequency alternating current delivery to achieve ablation of nerve tissue. At this point, the surgeon may then actuate the alternating current electrical field to cause exact target tissue heating where no heating is done to any other tissue. [0087] The electric field generator 100 is preferably small and miniaturized so that it may be easily held in one hand by the average adult person. For example, a standard 9-volt battery may be used to power an exemplary electric field generator 100 in order to achieve a desired cell injury.

[0088] Optionally, the high frequency alternating current medical device 91 will have two probes or needle-type projections 200 and the electric field generated by generator 100 will be single phase. A block diagram for this mode is depicted in Fig. 11. One probe or needle- type projection 200 would include one conductive segment 225 electrically connected to contact 107 on the electric field generator 100 and the other probe or needle-type projection 200 would include the other segment 225 electrically connected to contact 105 on the electric field generator 100. Alternatively, high frequency alternating current medical device 91 will have one probe or needle-type projection 200 and the electric field generated by 100 would be single phase. A block diagram for this operational mode is depicted in Fig. 11 A. The single probe or needle-type projection 200 would include both segments 225. In still other embodiments, the device 91 could have many more projections 200 and thus electric field generator 100 would need to have at least an equal number of signal outputs to utilize the many projections, each electrically connected to one probe or needle-type projection 200. For instance, each projection could emit one of many phase signals or one of many common signals produced by the generator, where a device 91 could have many probes or needle-type projections 200 to create intricate electric field combinations to help yield very specific desired precise cell injury. Device 91 could alternatively have many probes or needle-type projections 200 with only two signal outputs 105 and 107, where 105 and 107 signals are connected to the many projections in alternating fashion, perhaps along a row or arc of projections 200. Alternating only two signals in this fashion can create a large lesion area along the row or arc from only a one-phase alternating electric field because current is created between each projection 200 in this fashion.

[0089] An exemplary high frequency alternating current medical device 10 has three needle-type projections arranged in a line. See Figs. 15 and 16. The center projection 200 is electrically connected to electric field generator 100 by a common signal lead 107a. The two outer projections are electrically connected in parallel to the electric field generator 100 by a single-phase signal leadl 05a. A block diagram for the device of Figs. 15 and 16 is depicted in Fig. 12. In all arrangements and modes, the phase signal passes through the self-limiting conductive material electrical component 150 before entering the target tissue.

[0090] At least one probe or needle-type projection 200 may be removably attachable to the rest of the circuitry and structure of the high frequency alternating current medical device 91. Further, there may be a wide range of removably attachable at least one or needle-type projections 98, 200 (Figs. 14-16 of many different types, sizes, shapes, materials, etc. that are removably attachable to the rest of high frequency alternating current medical device. Thus, the invention includes a series of removably attachable tips 98, where each tip 98 comprises: at least one needle of projection 200 and at least two conductive segments 225 located thereon, where each is electrically connected to the rest of the device according to circuit diagrams on Figs 1 1-12 when attached onto medical device. The needles are adapted to penetrate beneath a patient's skin surface to access and/or engage nerves or other target structures beneath the skin and thus to deliver the heat, RF, or other energy to such structures. [0091] One such removably attachable tip 98' may be another nerve finder with two small electrically conductive electrodes or pads 99 on its distal end. Two small pads are used to electrically contact the surface of the target tissue to the electric field generator 100. Thus, the "nerve finder" tip 98' may be first used to find a nerve where a separate treatment tip 98 would then be attached to the device 91 to heat the nerve once located. [0092] The removably attachable tip 98 typically have a general conical shape or cup shape with an opening on the wide end of the cone and is flat on the narrow end of the cone to form an overall cup shape, where at least one needle-type projection 200 is attached to the exterior surface of the narrow end of the cone or bottom of cup. The distal end of high frequency alternating current medical device 91 , with tip 98 removed, may also have a general conical shape or cup shape, where device cone is slightly smaller than tip cone. Thus, the concave tapered section of tip 98 may then slide onto the convex tapered section of the device cone, where tip 98 snuggly fits onto device cone. Further, there may optionally be a securing mechanism such as a clasp means, snap means, lock means, or similar fastener to hold tip 98 onto the device cone in a very stable and secure fashion, so that surgery can be performed by the surgeon. Said securing mechanism would also have a release means so that removably attachable tip 98 may be removed. Thus, clasp means, snap means, lock means, or similar would have capability of releasing said means to remove tip 98. For instance with snap means, tip cone may be of a flexible nature to allow finger squeezing to cause deformity in tip cone thereby releasing one or more snap points between tip cone and device cone. When tip 98 is snapped into place onto device 91, an electrical connection occurs between at least two conductive segments 225 and generator signals 105 or 105a and 107 or 107a.

Removably attachable tips 98 may be supplied in a sterile condition and then disposed of after use.

[0093] The operating frequency of the pulse width modulation provided by the electric field generator 100 (Fig. 12) within about five percent using either trimmer input connection 109 or 111. The trimmer input connections 109 and 1 11 are electrically connected to a control module 125 which is powered by battery 97 and is electrically connected to electric field generator 100. Control module 125 includes one or more trimmer resistors or similarly functioning electronic components that are electrically connected to a frequency modulation control switch 127, which is a setting switch on the control unit 125 used to manually adjust the frequency of signal 105.

[0094] Control module 125 may also be configured to automatically adjust and stabilize the frequency of signal generated by 100 by sampling signal 105 and electrically processing it to determine whether the frequency is optimum. Signal and current from 105 is electrically filtered, processed, and analyzed where the result yields a signal input to adjust trimmer input 109 or 11 1. Thus, control module 125 creates a feedback circuit from signal output 105 to trimmer input 109, which results in automatic fine-tuning and stabilization of output. In the case of more than one output phase signal, a feedback circuit may have to be created for each output phase in order to automatically adjust and stabilize frequency of all phases. Control unit 125 optionally also determines if current through the target tissue is above a certain maximum preset limit and shuts down its electric field generation when said current goes beyond this limit. This is current cut-off setting 129 where the surgeon or technician may set a maximum current level where the device 10 shuts down its electric field generation above this level.

[0095] At least two electrical outputs: phase signal 105 and common signal 107 are used to perform the surgery. Outputs may be filtered, transformed, and otherwise electrically processed through standard circuit board components to yield desired precise cell injury. Phase signal 105 passed through self-limiting conductive material electrical component 150 on to the target tissue 250. It then travels through the target tissue 250 and back to the electric field generator 100 through common signal 107.

[0096] The self-limiting conductive material electrical component 150 regulates electrical current through the target tissue 250. As described above with respect to the first

embodiment, the, self-limiting conductive material electrical component 150 functions electrically like a thermistor, thermocouple, or switch.

[0097] If the preferred case of self-limiting conductive material electrical component 150 being a switch, the alternating current in the target tissue is completely shut down by 150 for a brief period of time until the target tissue has sufficiently cooled, thereby avoiding unnecessary cell damage, and then switch 150 would switch the alternating current in the target tissue back on again, thereby heating it up again, for a brief period, only to turn off again, repeating the process. This process essentially repeats many times per second yielding an overall steady state temperature in the target tissue. [0098] If the case of self-limiting conductive material electrical component 150 acting like a thermistor or thermocouple, the temperature changes of 150 do not lead to an abrupt off/on switching of alternating current in the target tissue, but rather yield a gradual heat increase or decrease as described below to control temperature of the target tissue and surrounding tissue. Thermistor has the most gradual fluctuations of alternating current. [0099] Self-limiting conductive material electrical component 150 consists essentially of a homogeneous blend of different materials, including a base material and a conductor dopant. Self-limiting conductive material electrical component 150 has a special combination of base and dopant that allows the resistance of a self-limiting conductive material electrical component to vary with its temperature. As current passes through the self-limiting conductive material electrical component 150, heat is produced in the self-limiting conductive material electrical component 150 as a result of electron, ion, or other charged- particle collisions occurring inside 150 as a result of the alternating current is passing through target tissue 250. Thus, increased current through target tissue 250 yields increased heat production in self-limiting conductive material electrical component 150. This heat causes structural changes in the molecules of the homogeneous blend of material, which in turn causes a change in conductivity of self-limiting conductive material electrical component. For instance with some self-limiting conductive materials or thermistors, heat causes the base material to expand, which separates a conductive dopant suspended therein, thereby reducing, and eventual cutting off, the electrical current passing there through. In other self-limiting conductive materials or thermistors, temperature change causes a phase change of base or dopant material, which causes structural changes at the molecular level yielding a switching effect from conductive to nonconductive or vice versa. [0100] At any rate, very special care must be taken to choose/design the best self-limiting conductive material electrical component 150 to yield the best mathematical characteristics between temperature and resistance, to yield to best surgical performance, i.e. the required temperature range to cause the desired precise cell injury. The relationship between temperature and conductivity of a self-limiting conductive material electrical component is typically nonlinear, so we use log scales to describe thermistor properties. Conductivity is typically measured by the inverse of such which is resistivity.

[0101] In the preferred embodiment, self-limiting conductive material electrical component 150 is made of PTC material. Fig. 7 is a graph of the electrical resistivity versus temperature of a PTC heater material suitable for our purposes. Suitability for typical procedures requires a resistivity that gradually increases with temperature as noted by the mid-level positive slope character of the graph. Further, there is an inflection point in the graph at To. As temperature rises above T_0; resistivity increases at a decreasing rate with temperature. Thus, there is a gentle decrease at a decreasing rate of electrical current passing through the target tissue as temperature rises above To. As temperature falls below To_, resistivity decreases at a decreasing rate with temperature. Thus, there is a gentle increase at a decreasing rate of electrical current passing through the target tissue as temperature falls below To. With reference to Fig. 7, going from To to T_H, resistivity gradually increases, thereby decreasing heat production in the target tissue. Likewise, going from To to T_L, resistivity gradually decreases, thereby increasing heat production in the target tissue. There is a mathematically stable temperature point at To, otherwise known as an inflection point. Materials with this inflection point relationship are preferred to provide optimal stability or the self-limiting conductive material electrical component at To, thereby producing a steady alternating current in the target area. [0102] The temperature of the self-limiting conductive material electrical component 150 determines the electrical current passing through the target area. Thus, the key design criteria of the high frequency alternating current medical device 91 is the determination of what minimum electrical current is required to produce the desired precise cell injury, then what self-limiting conductive material electrical component provides this quantity of current at it mathematical equilibrium, thereby determining the best self-limiting conductive material electrical component for the application of the high frequency alternating current medical device.

[0103] Different precise cell injury procedures may require different cell heating or electrical current operating ranges. For instance, different procedures may require different shaped and sized probes of needle-type projections 200, thereby changing current requirements, thereby changing the self-limiting conductive material electrical component requirements of the high frequency alternating current medical device 91. Different target tissues may require different current or heating thereby doing the same. Thus, certain procedures may require different self-limiting conductive material electrical component with different target temperatures To with different operating ranges TH to TL. These criteria may be adjusted by carefully choosing a PTC, NTC, or ZTC thermistor material for the high frequency alternating current medical device 91. Further, various dopants and various concentration of dopants may be used to vary characteristics to yield different resistance temperature graphs. Further combinations of PTC, NTC, and ZTC materials may be used to yield different resistance temperature graphs.

[0104] Fig. 9A includes the resistance temperature relationship of a NTC material. This arrangement may be used to create a maximum operating current as determined by temperature To with sharp cut-off at currents above such. Fig. 9B includes the resistance temperature relationship of a ZTC material. This arrangement may be used to create constant current across the target area at a certain level across a wide range of temperatures TH to TL. Fig. 9C includes the resistance temperature relationship of a NTC/ZTC material. This arrangement may be used to create a wide operating current range correlated to that of TH to TL with constant current at a certain level but with sharp cut-off at temperature T_L Fig. 9D includes the resistance temperature relationship of a PTC/ZTC material. This arrangement may be used to create a wide operating current range correlated to that of TH to TL with constant current at a certain level but with sharp increase in current at temperature TL thereby preventing the target tissue a certain temperature. [0105] PTC, NTC, and ZTC materials can be made from a crystalline or semi-crystalline polymer base material with certain conductive "doping" material added. With polymer based thermistors, transition temperature results from the melting or freezing of polymer molecules. With crystalline or semi-crystalline polymers, molecular structure is more tightly packed in solid phase and less tightly packed in amorphous phase or elastomer phase. Polymer molecules are generally non-conductive, so a conductive dopant must be added to make the material conductive. At temperatures below To, most polymer molecules are in solid phase, thus closely packed, thus at their most conductive state or level. At temperatures above To, most polymer molecules are in amorphous phase or elastomer phase, thus loosely packed, thus at their least conductive state or level. For the same choice of a matrix polymer, transition temperatures To generally coincide with the polymer softening point of the selected matrix polymer.

[0106] Dopant material is added to base material in order to render it conductive which allows the material to perform like a heating element. Also dopant is added to slow the resistance change or to widen the graph discussed above. Dopants are conductive material such as carbon black, metal oxide, semi-conductor material, blends thereof, or other material that is conductive and capable of being produced in small particles. The specific resistivity temperature relationships of PTC, NTC, and ZTC materials are arrived at by varying the type and concentration of dopant. Thus, a lower concentration or density of conductive particles in the polymer base composition is one way to obtain the desired gradual change in resistance for a self-limiting heater element. Generally speaking, dopant levels above 50% yield switch type material, dopant levels of 15-40% yield thermistor material, and dopant levels of 10% yield electro magnetic interference and or electrostatic discharge. Also, porosity, surface area, particle size, and oxygen content, of the conductive dopant may be varied to produce various properties. Also, more than one type of dopant may be added to base material.

Either the base material molecules or the dopant material particles may actually cause the heating in the thermistor. Thus, dopant may function to produce electron transfer or vibrational heating or both. All of these factors together with various carbon black loading levels and others results in a near endless amount of combinations between type(s) and amount(s) of dopant along with type(s) of base material to yield a near endless amount of specific resistivity temperature relationships.

[0107] PTC, NTC, and ZTC materials can also be made from a ceramic material or ceramic based material with conductive dopant added. Ceramic material can be conductive or not conductive depending on phase or structure. Ceramic material can be engineered to change phase from solid to elastomer or elastomer to solid at specific temperatures To. Typically, ceramic base material is barium titanate and/or related divalent titanates and zirconates.

Typical dopants include lead, strontium, rare earth metals, antimony, bismuth, or similar. Dopants are added to increase or decrease the anomaly range of the base material or further adjust the slope of the resistivity temperature relationship. Various ceramic thermistor heaters with different temperature resistivity relationships are commercially available. Also, a ceramic thermistor heater material manufacturer may endeavor to undertake special development programs to deliver specially desired characteristics.

[0108] In some modes, traditional switches are added to the tissue heating circuit or circuits or traditional thermocouples are placed near conductive segments 225 or both to further enhance temperature control of target tissue 250 or to add additional layers of safety current cut-off control or similar during electric field generation mode or surgical mode.

[0109] The high frequency alternating current medical device 91 (Fig. 13) typically includes a user interface 92 comprising a main power on/off switch 93, an electric field on/off switch 94, a main power indicator light 95, and an electric field indicator light 96. User interface 92 is electrically connected to control module 125 (Fig. 12), sending and receiving signals there from, and is indirectly powered by battery 97 through control module 125 electrical connections. Main power switch 93 engages power to electric field generator inputs and to control module 125. When switch 93 is on, power indicator light 95 is illuminated. Surgery may be performed when the electric fields are generated, which is controlled by the electric field on/off switch 94. When switch 94 is activated, the electric field is engaged between the at least one probe or needle-type projection 200. Electric field indicator light 96 illuminates when electric field on/off switch 94 in engaged.

[0110] As stated, the high frequency alternating current medical device 91 is preferably a hand-held battery powered single device. To facilitate this, all components are assembled onto one small circuit board. In this configuration, switches 93 and 94 may be located on the exterior of high frequency alternating current medical device 91 and at a location in close proximity to the index finger of the surgeon holding high frequency alternating current medical device 91. Lights 95 and 96 may also be located on the exterior of high frequency alternating current medical device 91. Frequency modulation setting 1 1 1 and cut-off setting (Fig. 12) may be located in the interior of device 91 because they are typically set differently for certain procedures and do not need to be adjusted during the procedure. [0111] In order to yield the most comfortably and logical instrument for a surgeon, the high frequency alternating current medical device 91 is preferably shaped like a pen. The delicate nature of producing a desired precise cell injury requires fine hand movements similar to that of writing in very small print. Thus, the surgeon that is comfortable writing with a pen is also comfortable using high frequency alternating current medical device 91 to yield desired precise cell injury.

[0112] The at least one probe or needle-type projection 200 typically has a diameter of 0.5 to 0.7 millimeters in outer diameter and length of 5 millimeters and up with a tissue piercing distal end. The surface of the at least one probe or needle-type projection 200 is non- conductive surface and thus does not emit an electric field except for at certain segments 225 of the probe or needle-type projection 200. Only at segments 225 will emit an electric field therefrom.

[0113] As described previously, at least two conductive segments 225 are required to generate electrical current in target tissue. In two embodiments of the high frequency alternating current medical device 91, at least two conductive segments 225 are both located on one probe or needle-type projection 200 or one segment 225 is located on each of two needle-type projections 200. Conductive segments 225 may have a layer or coating or alternately may not have a layer or coating that causes segments 225 to be conductive. For instance, the needles may be made of nonconductive material where conductive segments are formed by one or more conductive coatings thereon. Needles may be made of conductive material with nonconductive coatings on the surface except at conductive segments 225. Any assembly of conductive and nonconductive materials may be used to yield needles/probes with effective conductive segments 225. Segments 225 are electrically connected to signals 105 or 107. When segments 225 are located on the distal ends of probes or needle-type projections 200, heat is produced below the surface of the tissue only, thereby providing much more opportunity to cause the desired precise cell injury without also changing the surface of the tissue. Segments 225 are preferably located at the distal ends of needle-type projections 200 and are about 1-4 millimeters in length.

[0114] The method of using said high frequency alternating current medical device 91 comprises picking up said high frequency alternating current medical device 91, turning on said high frequency alternating current medical device, touching said at least one probe or needle-type projection 200 to the surface of target tissue 250, inserting said at least one probe or needle-type projection 200 beneath the surface of target tissue 250, or inserting said at least one probe or needle-type projection 200 into a body cavity 250, energizing said electric field generator 100 thereby inducing or generating an electrical alternating current in target tissue 250, disengaging the electric field generator 100, removing said at least one probe or needle-type projection 200 from said target tissue 250, and repeating the former steps as necessary to cause the desired certain desired precise cell injury. Optionally, a low power dc current can be used to locate a nerve of interest prior to delivery of the alternative current.

[0115] A high frequency alternating current medical device constructed according to the present invention may be used by touching at least one probe or needle-type projection 200 to target tissue 250, whether on the skin surface of a patient, subcutaneously or deeper. If the target tissue is skin or subcutaneous tissue, a specific type of probe and temperature may be chosen to achieve skin tightening, resurfacing or collagen remodeling. The maintenance temperature of the device could be chosen to be not more than 41° C (106° F). At such a moderate temperature 200 can produce skin tightening, skin resurfacing and collagen remodeling, for dermal regeneration and cosmetic applications. This can also be

accompanied by mechanical ablation of skin surface cells. Alternatively, a higher temperature could be used to cut skin, while simultaneously cauterizing any bleeding.

[0116] If the target tissue is subcutaneous adipose (fat) tissue, the at lest one probe 200 must have a tissue-piercing structure to be inserted transcutaneously into the skin to cause selective damage to fat cells proximate to the end of 200.

[0117] The target tissue might be any of the tissues set forth previously with respect to the first embodiment. The second embodiment is particularly suited for locating and treating nerves.

[0118] The target tissue might be any organ system in the body, such as heart, lungs, brain, eyes, kidney, liver, ovaries, thyroid, bladder, uterus, stomach, intestines, appendix, gall bladder, or similar.

Claims

WHAT IS CLAIMED IS: L A medical heating device comprising:

a hand-held enclosure;

a power source within the enclosure;

a heat conductive probe extending from an end of the enclosure, said probe having a tissue contacting distal end; and

a temperature change coefficient (TCC) element forming a miniaturized heater having a change in resistance in the range from two to four orders of magnitude in response to a temperature change in the range from 20 C° to about 80 C°;

wherein the heat conductive probe is coupled to the TCC element to conduct heat from the TCC element to the tissue contacting distal end.

2. A medical heating device as in claim 1 , wherein the TCC element comprises a PTC or NTC/ZTC element which changes in resistance in response to a rise in temperature and which is composed of:

a thermistor heater material comprising a polymer base material with from 5% to 40% conductive dopant material, a ceramic base material with from 5% to 40% conductive dopant material in a ceramic material without dopant material, wherein, said thermistor heater material is characterized by an electrical resistance that varies with temperature, wherein said variance in turn causes a variation of the heat production from said element.

3. A medical heating device as recited in claim 1 , wherein said electrical power supply is a direct current battery.

4. A medical heating device as recited in claim 1 , wherein said enclosure comprises a thermally-insulating j acket.

5. A medical heating device as recited in claim 1 , wherein said TCC element has physical form of at least one coil wound around a core electrical spacer wherein said core electrical spacer functions to electrically separate some areas while electrically connecting other areas of said TCC element to said electrical power supply to yield an electrical current path through the length of said at least one coil.

6. A medical heating device as recited in claim 1 , wherein said TCC element has physical form of a sheet wrapped around a core electrical spacer, with opposite ends of said sheet being connected to said electrical power supply to provide an electrical current path through the entire sheet.

7. A medical heating device as recited in claim 1 , wherein said TCC element has physical form on an elongated core with longitudinal channels running therethrough to house said means for electrically coupling said TCC element to the power source and said heat conductive probe, so as to provide a current path through said elongated core where the probe has an electrically-insulating sheathing covering areas of it adjacent to said TCC element.

8. A medical heating device as recited in claim 1 , wherein said heat conductive probe comprises one or more needle-shaped probes.

9. A medical heating device as recited in claim 9, wherein said thermally- conductive probe comprises at least one hollow tube adapted for delivering or removing material from the target tissue.

10. A medical heating device as recited in claim 9, wherein said thermally- conductive probe has cross-sectional shape that is circular, oval, square, rectangular, or oblong.

1 1. A medical heating device as recited in claim 9, wherein said thermally- conductive probe has a distal end that is rounded, roller-balled, piercing, pointed, or blunt.

12. A method for delivering heat to a tissue location, said method comprising:

providing a medical heating device as in claim 1 ;

passing current from the power source through the TCC element so that the TCC element heats;

engaging the tissue contacting distal end of the heat conductive probe against the tissue location;

wherein heat is delivered to the tissue causing the probe to cool which causes the TCC element to cool and display a temperature change which in turn causes the resistance to change and return the temperature of the TCC element to a control point.

13. A high frequency medical heating device comprising: a hand-held enclosure;

a power source within the enclosure;

an electrical field generator which draws current from the power source and generates radio frequency current;

at least one tissue probe;

at least two conductive segments on one or more tissue probes; and a temperature change coefficient (TCC) element having a change in resistance in the range from two to four orders of magnitude in response to a temperature change in the range from 20 C° to about 80 C°;

wherein the TCC element is in series between the electric field generator and the at least two conductive segments.

14. A medical heating device as in claim 13, wherein the TCC element comprises a NTC/ZTC or PTC element which changes in resistance in response to a rise in temperature and which is composed of:

a thermistor heater material comprising a polymer base material with from 5 to 40% conductive dopant material, a ceramic base material with from 5 to 40% conductive dopant material, or a ceramic material without dopant material, wherein, said thermistor heater material is characterized by an electrical resistance that varies with temperature, wherein said variance in turn causes a variation of the heat production from said positive temperature coefficient element.

15. A medical heating device as recited in claim 13, wherein said electrical power supply is a direct current battery.

16. A medical heating device as recited in claim 13, wherein said enclosure comprises thermally insulating jacket.

17. A high frequency alternating current medial device as recited in claim 13 with two tissue probes and two conductive segments where each probe has one conductive segment located thereon.

18. A high frequency alternating current medical device as recited in claim 13 with three tissue probes and three conductive segments where each probe has one conductive segment located thereon.

19. A high frequency alternating current medical device as recited in claim 13, wherein said at least one tissue probe and at least two conductive segments located thereon are removably attachable to the enclosure.

20. A medical heating device as in claim 13, comprising at least two interchangeably tissue probe assemblies.

21. A medical heating device as in claim 20, comprising a first tissue probe assembly with one or more tissue-penetrating tissue probes and a second tissue probe assembly with one or more surface-engaging tissue probes.

22. A medical heating device as in claim 13, wherein the electrical field generator is adapted to selectively produce a direct current which can stimulate and locate nerves and produce high frequency current to treat the nerve located by the direct current.

23. A method for heating tissue comprising:

providing a high frequency medical heating device as in claim 13;

passing radio frequency current from the electric field generator to the tissue probe; and

engaging the two conductive segments against tissue to ohmically heat the tissue;

wherein the TCC element controls the current flow to the two conductive segments to maintain the current flow in a desired range.

24. A method for treating nerve tissue with radio frequency current, said method comprising:

providing a high frequency medical heating device as in claim 22;

passing direct current form the electric field generator to the tissue probe; engaging the two conductive segments against tissue to stimulate a target nerve;

observing the location where the nerve is stimulated; and

passing radio frequency current form the electric field generator to the tissue probe while the probe is at the observed location; wherein the TCC element controls the current flow to the two conductive segments to maintain the current flow in a desired range.