WO2008151469A1

WO2008151469A1 - Heating device and method using a pseudo-uniform electromagnetic field

Info

Publication number: WO2008151469A1
Application number: PCT/CN2007/001883
Authority: WO
Inventors: Changxue Ren
Original assignee: Changxue Ren
Priority date: 2007-06-15
Filing date: 2007-06-15
Publication date: 2008-12-18

Abstract

A microwave heating device and a microwave heating method for evenly heating an object, such as a person's body involve use of at least one microwave source (2) that outputs multiple microwaves and an antenna array (3) that radiates substantially plane microwaves to form a pseudo uniform microwave electromagnetic field (15), wherein the microwaves are not frequency-correlated, in order to eliminate non-uniform heating caused by interference. The antenna array (3) includes multiple antenna units (14), and each antenna unit (14) includes at least one microwave radiator (10) and at least one converter (11) that converts the spherical microwave field into a plane microwave field. A computer based control system (1) and redundant temperature monitoring subsystems (5) can be used to adjust the output of each antenna unit (14), in order to enhance the uniform heating effect. The device also includes a pressure monitor and/or a heart rate monitor (6) that resist microwave interference for the safety of the hyperthermia-treated subject.

Description

HEATING DEVICE AND METHOD USING A PSEUDO-UNIFORM ELECTROMAGNETIC FIELD

Technical Field

[0001] The present invention relates generally to improved microwave heating devices and methods, particularly to a microwave heating apparatus and method for using microwaves to heat a lossy medium or a conducting medium by forming pseudo uniform microwave electromagnetic fields, which can be adjusted to provide even heating of a large mass or a localized region of a medium that absorbs at least some of the microwave energy.

Background of the Invention

[0002] Microwave heating can be used to selectively deliver energy to certain types of molecules having dipole moments, such as water; the result of absorption of this energy is an increase in temperature, thus microwaves can be used to heat a portion of a lossy medium, such as the human body. It is also well known that a modest increase in temperature, such as heating to 42-44⁰C, can cause cancer cells to become much more susceptible to various methods of injuring or killing cells; thus increasing the temperature of a person's body during a cancer treatment can enhance the effectiveness of the treatment. One way to heat cancer cells in vivo is thus to apply microwave energy to the cells, which can be used for hyperthermia.

[0003] Since 1980, various hyperthermia methods have been developed to raise the temperature of part or all of the body of a cancer patient. These methods have been used locally (i.e., within a small area, such as directly in tumor tissue), regionally (in a larger portion of the body, such as a particular limb where a tumor is located), and even for the entire body of the patient (whole-body hyperthermia). Local and regional hyperthermia methods attempt to selectively warm a targeted tumor directly, without substantially affecting the rest of the patient's body. Whole-body hyperthermia is often used as a systemic treatment for a cancer condition that is delocalized or has metastasized. These methods have been shown to reduce some of the adverse effects caused by radiation and chemical cancer therapies, and to make these therapies more effective. Recent basic and clinical research shows that whole body hyperthermia may be widely applicable as an adjunct treatment used in combination with conventional chemotherapy and ration treatments, as methods for providing whole-body hyperthermia temperatures improve.

[0004] Heating methods used for hyperthermia treatments include exposure to warm air or water, as well as application of heat in the form of electromagnetic radiation, including infrared and microwave radiation. Microwave heating has been most effectively used for localized heating, where various means for focusing the microwave energy in and around the targeted tumor have been used. See, e.g., U.S. Patent No. 5,571,154. Heated air or water tend to be too slow and uncomfortable for patients to endure. Most of the traditional whole-body hyperthermia devices use infrared (IR) heating technology. For example, ET-SP ACE™, one of the whole- body heating apparatus manufactured by ET Medical Corporation of the P.R. China, is a hyperthermia apparatus using infrared radiation to heat a patient's body. This system raises body temperature by exposing the body to specific infrared frequencies. The infrared energy is absorbed at the surface of the skin, and the heated skin gradually transfers the heat to the fat and then to the muscle by conductive heat transfer. The heat is then slowly transferred to the inside of body where it warms the blood, which gradually increases the whole body temperature. Other devices known in the art utilize microwave energy to heat the body of a subject, but are generally designed to focus microwave energy in a local or regional treatment, e.g., U.S. Patents No. 4,586,516; 4,589,423; 4,669,475; 4,672,980; and 4,798,215; and 4,860,752 appear to relate to localized treatment methods, and contemplate ways to utilize interference to focus energy selectively on a tumor to be treated.

[0005] However, there are several shortcoming with this type of device:

1. The infrared radiation cannot penetrate the skin, nor does it penetrate the fat or muscle. It relies on heat transfer from the skin, and the skin can only be heated modestly before pain and injury thresholds are exceeded.

2. The skin of a human body can incur severe skin burns when exposed to temperature higher than 46⁰C for a long period of time, while muscle and other tissues will suffer if maintained at temperatures above about 43⁰C. Hence, the temperature inside an infrared treatment chamber can not be over about 45⁰C for safety reasons. However, the normal human temperature is around 37⁰C. This means the temperature difference between the treatment chamber and human body is no more than about 8⁰C. As a result, heat transfer during such treatments is very slow, which results in long heating time - thus a single IR hyperthermia treatment usually last for 5-6 hours, because the body temperature increases very slowly toward the level where a significant hyperthermia effect occurs. Thus this method risks skin burn and other injuries, and stresses the entire body for a long period of time.

3. It is intolerable for a patient to stay inside an enclosed IR treatment chamber at 45⁰C for 5-6 hours, so the patient must be put into deep anesthesia which adds additional stress and risk for the cancer patient, in addition to the stresses caused by the primary radiation or chemotherapeutic treatment that is being used.

4. The reported incidence of adverse effects from heating a subject with the ET-SPACE™ systems is 10.6%, consisting of 2nd degree skin burns and bedsores.

5. The infrared based device has limited application in that it cannot be used to perform regional hyperthermia. Thus a cancer treatment facility must have separate devices in order to provide local / regional hyperthermia treatments and whole-body hyperthermia treatments.

[0006] There is thus a need for improved methods and devices for heating a subject's whole body during hyperthermia treatments. Improved methods and devices should provide at least some of the following advantages: faster heating time, to achieve an effective body temperature more quickly; decreased risk of injuries caused by localized heating; reduced discomfort so that patients may not require prolonged or general anesthesia during hyperthermia treatment; and the flexibility to use a single device for both local / regional treatments and for whole-body hyperthermia treatments. The present invention provides devices and methods that offer such advantages. In addition, it provides additional features that increase the flexibility of the apparatus of the invention, and that increase the comfort and safety of a subject undergoing hyperthermia treatment with the apparatus.

Summary of the Invention

[0007] An object of the present invention is to overcome the shortcomings of the existing hyperthermia technology by providing a microwave heating apparatus and method that can produce a pseudo uniform microwave electromagnetic field that can be used to heat a targeted subject or other object. The uniform field is produced by an array of at least two, and preferably at least four or more, antenna units.

[0008] Another object of the invention is to enhance the functionality of the microwave heating apparatus to better adapt it for use in regional or local therapy, while retaining its ability to provide whole-body hyperthermia treatments. Another object of the invention is to provide features that enhance the comfort and safety of a subject being treated with the microwave output of the device.

[0009] Microwave energy is used by the devices and methods of the invention, because it is absorbed within the body, unlike infrared energy, which is absorbed almost entirely at the surface of the skin. A generally uniform field is used to deliver heating energy over a large area, permitting relatively rapid heating of a region or of the whole body. The microwaves in this generally uniform field penetrate through skin and fat, and can further penetrate 2-3 cm inside the muscle, hence their energy is absorbed within a relatively large volume of tissue, allowing delivery of a larger amount of energy than can be achieved by infrared technology, without excessive localized heating. Moreover, since heat is absorbed in a larger volume of tissue, it more quickly transfers heat into the blood to further accelerate distribution of the heat to portions of the body that do not receive substantial amounts of microwave energy. As a result, the time required to elevate the body temperature of a treated subject is greatly reduced, without localized heating of the skin that causes injury in an infrared heating device.

[0010] The pseudo uniform microwave electromagnetic field used in these devices and methods is formed using principles of non-interfering electromagnetic wave theory. The devices include one or more arrays of antenna units that are individually controllable, and that deliver substantially planar microwaves that are not frequency correlated and/or that are not phase correlated.

[0011] The system is adapted to provide microwaves from each antenna unit that are non- interfering with respect to overlapping microwaves from other antenna units. The non- interfering microwaves can be produced by avoiding phase correlation of microwaves that overlap, or by avoiding frequency correlation for microwaves that overlap. Avoiding phase correlation eliminates constructive and destructive interference between waves from different antennas, which minimizes 'hotspots' and 'cold spots' that would develop where in-phase microwaves overlap. Alternatively, providing microwaves that are not correlated in frequency also eliminates constructive and destructive interference between waves from different antennas. As another alternative, a combination of different phases and different frequencies can be used to provide non-interfering microwaves.

[0012] The microwave frequency of the methods and devices of the invention can be any frequency or frequencies between about 0.1 GHz and 20 GHz. In some embodiments, each frequency can be in the range of about 2 GHz to about 3 GHz, such as about 2450 MHz. [0013] The devices and method use a microwave source (or sources) that will ultimately provide microwaves that are non-interfering, where such non-interfering microwaves will be radiated by the antenna units of the antenna array. The microwave source (or sources) has a microwave output or multiple outputs that is/are suitable for generating non-interfering microwaves that are not phase correlated and/or not frequency correlated.

[0014] The device provides multiple microwaves directed toward an object to be heated. A microwave source having only one output can be used to provide multiple microwaves by splitting the single output into multiple outputs with a splitter. Once the microwave energy from a single source is split into two or more outputs, at least one and optionally more than one of the outputs is then modified in frequency or phase or both, so that their phase and/or frequency are not correlated with the phase and/or frequency of a microwave that can overlap with it when in use. Thus if, for example, the microwave output of antenna unit A can overlap during operation with that from antenna unit B, the microwave outputs from those two antenna units should be non-interfering with respect to each other. This can be accomplished by adjusting the phase, frequency, or both of the microwave output of at least one of the two antenna units. Methods for adjusting the phase and/or frequency of the microwaves are well known in the art.

[0015] Alternatively, multiple microwave generating sources may be used to provide a suitable number of non-interfering microwaves, that are adapted in phase and/or frequency to be non-interfering. Likewise, a combination of, e.g., two sources or three sources with one or more splitters may also be used to provide the desired number of separate microwaves to feed into an array of antennas.

[0016] Once multiple microwaves are produced, the phase and/or frequency of the signals can be adjusted to avoid phase correlations and/or frequency correlations between the microwaves before they reach the antennas of the antenna unit. This can be done by employing one or more random phase shifting devices, or a random phase generator, to adjust phasing of at least some of the microwaves before they reach the antenna units; frequency correlations can similarly be avoided between two antenna units by changing the frequency of one of then to a different fixed frequency from the other, or by varying the frequency of one randomly or systematically while the other remains fixed, or even while the other frequency is varied in a way that differs from the first. In some embodiments of the invention, the frequency of the microwaves from one antenna unit is different from the frequency of each antenna unit whose output substantially overlaps with that unit's output; in others, each of the microwave antenna units provides a microwave output that is not phase correlated with any other antenna unit that operates at the same time.

[0017] In one aspect, the invention provides a microwave source that produces a multiplicity of non-interfering microwaves, which device comprises a source of microwave energy, a splitter to separate the microwave energy into a multiplicity of separate microwaves, and a frequency modulator that changes the frequencies of at least one of the microwaves so that at least two of the separate microwaves are non-interfering. The microwave source (or sources) with a microwave output or multiple outputs provides power that is suitable for heating a person's body rapidly enough to provide effective hyperthermia treatment as either whole-body or local or regional treatment. In such treatments, the total power of the device is provided by one or more microwave sources, and the microwave energy may be divided and distributed by a number of different antenna units. Thus each antenna unit may radiate less power than is output by hyperthermia devices of the prior art; however, because there can be many antenna units, the net result is efficient and rapid heating of the body without creating localized hotspots. In addition, because the power output by the individual units can be individually controlled, the user can electronically adjust the electromagnetic field so it is applied only by certain antenna units, which deliver microwave energy only to selected portions of the object. This permits the device to adjust energy input into the subject to achieve a desired temperature distribution. It also permits the devices of the invention to be used for regional hyperthermia treatments, or even directed to one localized portion of the body such as a limb.

[0018] In order to provide a pseudo uniform microwave field over a large area, the devices include an antenna array or multiple arrays. Each antenna array consists of multiple antenna units. Each antenna unit comprises at least a microwave radiator that radiates a spherical wave, and at least a converter that converts the spherical microwaves to plane microwaves which are directed toward a targeted object. Thus each antenna unit provides a plane wave output, and the outputs of various units are non-interfering. The array of antenna units delivers plane waves over large portions of a targeted object such as a hyperthermia patient's body.

[0019] The antenna units are distributed relatively evenly around or at least on one side of a targeted subject or object, to deliver microwave energy onto and into the target to be heated. This reduces localized overheating and potential for injury. Because the antenna units produce plane wave outputs, the output power is mostly directed in an output column directly in front of the antenna unit. Properly spacing the antenna units apart reduces the overlap of the output columns of adjacent antennas. The antenna units in an array are generally separated by a distance that reduces overlap between the output columns of microwave output from other antenna units. This reduces interference between microwaves from different antennas, by minimizing the overlap between the microwave fields from different antenna units. Avoiding phase matching or phase correlation between at least adjacent antenna units further reduces such interference, to provide a uniform microwave field.

[0020] The antenna units may also be positioned within a structure that is at least partly microwave reflective. This permits the device to more efficiently direct microwave energy to the treated subject.

[0021] In some embodiments, at least one antenna unit is partially surrounded by a microwave-reflective structure that is shaped so that the reflection of spherical or cylindrical microwaves converts the spherical microwaves into substantially planar microwaves. For example, one or more antenna units may be positioned along a linear axis, and the microwave- reflective structure can be shaped with a parabolic cross-section and positioned so that it reflects spherical or cylindrical microwave output from the antenna units to provide a substantially planar microwave field that can be directed onto a subject to be heated.

[0022] Alternatively, two antenna units may be positioned at the foci of an ellipse-shaped microwave-reflective structure that serves to convert output from each of the antenna units into substantially planar microwaves.

[0023] The power density and the distribution of the power density of the microwave electromagnetic field are adjustable, by a control system that controls the energy output of each antenna unit in the array. This results in quickly raising body temperature while the patient feels comfortable without deep anesthesia: it does not rely primarily on heating the subject's skin, which is rich in pain receptors and thus particularly heat sensitive. Furthermore, it greatly shortens the treatment time and it does not cause skin burns to the patient, thus it addresses many of the shortcomings of previous technology.

One aspect of the invention provides a microwave diathermy device for heating a lossy or conducting medium, said device comprising: a) at least one microwave source that provides microwaves through a multiplicity of microwave output ports, wherein each output port is operatively connected to deliver microwaves to an antenna unit; and b) a plurality of microwave radiating antenna units; wherein, each antenna unit comprises a radiator to produce a non-planar microwave, and a converter to convert the non-planar microwave into a substantially plane microwave, wherein the frequency of the microwave output of any antenna unit is not correlated in frequency with the frequency of the microwave output of the other antenna unit whose microwave field overlaps with the microwave field from the first antenna unit.

[0024] In some embodiments, the device further comprises a temperature monitoring subsystem and a computer based control system that receives input from the temperature monitoring subsystem, and the computer based control system is adapted to adjust the power output of one or more of the antenna units in response to input from the temperature monitoring subsystem, and the temperature monitoring subsystem is adapted to measure a temperature of at least one portion of the medium while the device is in use.

[0025] In some such devices, the microwave source produces multiple microwaves, wherein the microwaves are not correlated in frequency, or the microwave source produces a single microwave that is split into multiple output microwaves, and the frequency of at least one microwave signal is modified before that microwave is radiated from an antenna unit.

[0026] Typically, the device is configured so that the antenna units are oriented to direct the substantially plane microwaves toward a surface of a targeted object to be heated, and the antenna array is configured to provide a pseudo uniform field of microwaves over the majority of one aspect of a lossy medium to be heated. This is suitable for whole-body hyperthermia treatment. Frequently, the medium is a human subject who is to receive a hyperthermia treatment, which may be whole-body or local or regional. Therefore, in some preferred embodiments, the antenna array is sized to provide a pseudo-uniform microwave field large enough to provide whole-body hyperthermia. Thus the array of antenna units may be sized and configured to correspond in size and shape to the outline of a typical human being, which may be a child or an adult. Often the array of antenna units is sized to provide a pseudo-uniform microwave field over an area of at least about 3 square feet or four square feet, and some embodiments provide a microwave field that covers an area of at least about 6 square feet. Often, the array of antenna units comprises at least four antenna units, and the computer based control system is adapted to control the output power of each antenna unit. Optionally, these devices have a continuously adjustable output power and produce a microwave field comprising one or more frequencies in the range of about 0.1 GHz and 20 GHz. Often, the devices operate in a frequency range of 0.5 to 10 GHz. In many embodiments, at least one antenna unit outputs a microwave in the frequency range of 2-3 GHz, and often it comprises at least one microwave source that produces microwaves having a frequency between 2 GHz and 3 GHz. [0027] Each antenna unit typically includes at least one converter for transforming a spherical microwave, which is radiated by the antenna unit into a planar microwave. The converter may operate by either reflective or refractive principles, or by a combination of these principles. In many embodiments of the present invention, the functional element of the converter that performs this transformation comprises a reflective element that converts a spherical microwave to a substantially planar microwave.

[0028] In many embodiments, the devices of the invention further comprise a temperature monitoring sub-system that provides a temperature sensor associated with each antenna unit, and they may also comprises a computer-based controller that is adapted to adjust the output of each antenna unit to achieve a desired temperature distribution in the medium, such as a subject receiving hyperthermia treatment. In addition, the device may comprise one or more blood pressure-monitoring devices and one or more heart-rate monitoring devices. The temperature sensors, blood pressure monitoring devices, and heart-rate monitoring devices may be adapted for a portion of their sensors to be positioned within the microwave field of the device so they can conveniently be used to monitor the condition of a hyperthermia-treated subject during treatments that involve delivery of microwave energy to the portion of the body that is proximal to the sensor(s).

[0029] Frequently, the antenna units of the devices of the invention are held in place by a support structure that permits the position and/or angle of at least one of the antenna units to be adjusted. Optionally, the support structure is adapted to permit the antenna units to be adjusted in either position or angle relative to one another in order to optimize the size and shape of the microwave field for each subject or object to be heated. Where reflective principles are used to produce the substantially planar microwaves, the support structure may also serve as part of the reflective converter that converts spherical microwaves into plane microwaves.

[0030] The multiplicity of output ports required to provide inputs to the antenna units of the array may be on one microwave source, or they may be on a splitter or other device that receives microwaves from a microwave source and participates in delivery of the microwaves to one or more antenna units. More than one microwave source can be used, such as one source for each antenna unit; or a combination of more than one source with one or more splitters may be used to provide a microwave input for each antenna unit.

[0031] Optionally, the device may also include a computer-based real-time control system and/or a temperature control sub-system, which may be connected together to allow the control system to adjust the output of the antennas to provide a desired heating rate, temperature, or temperature distribution within the heated object. The device may provide a pseudo uniform microwave field for heating the object. It may be configured to direct this microwave field onto at least one aspect, or at least a majority of one aspect of the object to be heated; and that object may be a human subject to be treated using hyperthermia.

[0032] Another aspect of the present invention provides a method of forming a pseudo uniform microwave electromagnetic field for heating an object. This method uses one or more microwave sources to produce multiple microwaves that are not correlated in phase and/or frequency. The multiple non-interfering microwaves that are non-phase correlated and/or non- frequency correlated are delivered to an array of antennas, or to multiple arrays of antennas, which are used to distribute the microwaves relatively uniformly over a target, such as a hyperthermia patient's body. The antennas radiate substantially plane waves, so they provide a more uniform microwave field than devices known in the art. Because an array of antennas is used, controlling the individual antennas permits the microwave energy to be selectively delivered to each region of the targeted object, thus enabling the user to achieve a desired temperature distribution within a relatively large object.

[0033] The device may provide microwaves within the range of about 0.5 to 10 GHz, preferably in the range of 2 GHz to 3 GHz, such as 2.45 GHz. It may utilize any suitable number and arrangement of antenna units to produce the microwave field, preferably by producing plane microwaves, and typically using at least four antenna units in an arrangement that may be sized suitably for producing a microwave field large enough to cover the majority of a hyperthermia subject's body. The plane microwaves may be produced as spherical microwaves by conventional antennas, and then converted by a converter into plane waves. Suitable converters may use a dielectric material having a refractive index greater than one; preferably the dielectric material has a refractive index of 1.2 to 1.3. In some embodiments, the converter comprises a reflective element, and uses reflective principles to convert the spherical microwave into a substantially planar microwave.

[0034] The devices of the invention are adapted to provide a microwave field comprising a plurality of substantially planar microwaves radiated by an array of antenna units. Each of the antenna units in the array comprises at least one microwave radiator. Typically, the microwave radiator, produces a spherical microwave, and the spherical microwave is converted by a converter into a substantially planar microwave. Alternatively, the microwave radiator may produce a cylindrical microwave, which is then converted into or used as a substantially planar microwave. In some embodiments, the antenna produces a substantially planar microwave and requires no converter. In some embodiments, the antenna units may include a mixture of different microwave radiators operating by any of these principles, provided that the antenna units produce a pseudo-uniform microwave field that preferably consists of substantially planar microwaves. In preferred embodiments, each antenna unit produces a spherical microwave and includes at least one converter that converts a spherical microwave to a plane microwave. Hence, each antenna unit receives a microwave input from a microwave source, and radiates a substantially planar wave, which is directed toward the treated subject or object.

[0035] In addition, the device may include a temperature monitoring subsystem, such subsystem can use various temperature sensing technologies such as but not limited to thermistor, infrared sensor, MRI etc. to monitor temperature of the lossy object. In preferred embodiments of the apparatus, the temperature monitoring subsystem utilizes at least two different temperature-sensing technologies to increase the safety of the subject being treated. Preferably, two sensors that employ different temperature-sensing technologies are used to monitor the temperature of one portion of the subject or object being heated. This provides redundancy in case one sensor fails, and also provides confirmation that the sensors are properly calibrated and operational.

[0036] At least one temperature sensor is placed either in contact with or not in contact with the medium to be heated by the array of antennas so that it measures a temperature of at least one portion of the medium to be heated. The temperature monitoring subsystem monitors heating to determine where a target temperature has been achieved, for example, and is operatively connected to a control system. The control system uses this temperature information from the temperature monitoring subsystem to adjust the power output of individual antennas in the antenna array. By adjusting the power density and the distribution of the power density of the planar microwaves from individual antenna units using electronic scanning, this method can be used in both whole body hyperthermia (including the body and limbs) and regional hyperthermia.

[0037] Another object of the present invention is to provide an apparatus that uses at least one array of antenna units to achieve a desired temperature distribution in a relatively large object, such as a person's body. The desired temperature distribution may be uniform throughout the targeted object, or it may include localized elevation of temperature of certain regions within the object. The apparatus includes one or more antenna arrays, consisting of multiple antenna units, and a microwave energy source that provides a multiplicity of microwave signals to power the antennas in the array. Each antenna unit comprises a microwave radiator that radiates a spherical wave, and a converter that converts the spherical microwave to plane microwaves which is used toward a targeted object. The microwave source typically includes more than one output port, or feeds into a splitter that divides the signal into more than one output. The microwave output is directed to the antenna units, which then output non-interfering microwaves, which are not correlated in phase or frequency. The apparatus may also include a computer based real-time control system and a temperature monitoring subsystem. The temperature monitoring subsystem can comprise one or more temperature measuring devices using various temperature measuring technologies that are adapted to measure a temperature of at least one portion of the targeted object.

[0038] Another aspect of the invention provides a method to establish a desired temperature distribution in the body of a subject by forming a pseudo uniform microwave electromagnetic field to heat at least a portion of the subject's body. Often, the method comprises the following steps: providing a microwave source that produces non-interfering microwaves . providing at least one array of microwave antenna units, wherein each antenna unit receives microwaves from the microwave source and produces a substantially plane microwave, wherein the power output of each antenna unit can be adjusted by a computer based control system; providing a temperature monitoring sub-system adapted to measure the temperature of at least one portion of the body of the subject, wherein the temperature monitoring subsystem provides temperature information to the computer based control system; directing the substantially plane microwaves to form a pseudo uniform microwave electromagnetic field incident upon the subject to be heated; and adjusting the power output of the antenna units in response to information from the temperature monitoring sub-system to achieve the desired temperature distribution in the targeted subject.

[0039] Optionally, the method further comprises providing at least one heart rate monitor and/or at least one blood pressure monitor, and these are used to monitor the condition of the treated subject without interrupting treatment or exposing the health care provider to the microwave field. Optionally, the heart rate monitor and/or blood pressure monitor can be configured to produce a warning signal or alarm to alert a user to undesired levels or changes in the subject's blood pressure and/or heart rate, and may also be adapted for use in the microwave field or shielded to prevent microwaves from interfering with the operation of the monitor.

[0040] The method may be used to produce a pseudo uniform microwave field sized to heat the entire body, or the majority of the body, of a subject to be treated with hyperthermia. Alternatively, it may be used to create a localized heating center in the body of a subject to be treated with hyperthermia. Preferably, these methods use at least two redundant temperature monitoring sensors at one single point to provide accurate temperature data in case one fails. The temperature at multiple points of the subject are monitored. When used for localized heating, the methods often use two or more temperature sensors to monitor the temperature of the subject near the portion of the body where localized heating is desired.

[0041] Another aspect of the invention provides a method to use microwave energy to elevate the temperature of a subject's body, characterized by use of substantially planar microwaves delivered by an array of antenna units that direct the microwaves onto a majority of one aspect of the subject's body, wherein the microwaves are not correlated in frequency. Typically, where microwaves from two antenna units of the array would overlap in use, the two antenna units radiate microwaves that are not correlated in frequency, or that are not correlated in phase, in order to avoid overheating caused by interference where the microwave fields from the two antenna units overlap.

[0042] The method can further incorporate using a temperature monitoring subsystem, such as a multiplicity of temperature sensors. The temperature monitoring subsystem typically measures a temperature at one or preferably more than one location in or on the object to be heated. The method can also incorporate using a control system such as a computer-based realtime control system that uses the temperature measurements to adjust the power output of some of the antenna array, or of some or all of the antenna units in the array, to achieve the desired temperature distribution in the heated object. In some embodiments, the method is used to provide a hyperthermia treatment to a subject in need of such treatment. Frequently, the temperature monitoring subsystem in such embodiments includes multiple temperature sensors in contact with or not in contact with the subject, but measuring a temperature of a portion of the subject's body. These temperature measurements are delivered to a control system, which uses this information to adjust the power output of one or more antenna units to facilitate producing a desired temperature distribution or rate of temperature change in the treated subject. These methods are frequently used to treat a subject having widespread, or metastasized or delocalized cancer, and are often employed in combination with a radiation or chemotherapy treatment method, and to enhance the effectiveness of the radiation or chemotherapy treatment.

[0043] The control system can be used to provide electronic scanning, which refers to using the temperature monitoring subsystem to measure the temperature of a subject's body at one or more positions on or in the body, and feeding those temperature measurements to the control system, which uses the temperature information to adjust the power output of the individual antenna units in the antenna array. By controlling power output by the microwave source(s) and by the individual antenna units, the control system ensures that the targeted subject's body is heated to a sufficient temperature without injury.

[0044] The output of a non-interfering microwave source is connected to each antenna unit; the radiator in the antenna unit produces a spherical microwave and the converter converts the microwave into a plane wave, that impinges on the targeted object. The array comprises multiple antenna units that may be held in position by a frame, and may be of any shape or arrangement suitable for a particular use. Figure 2 provides an illustration of one embodiment of a frame carrying an array of antenna units.

[0045] The devices and methods of the invention thus provide an array of antenna units that receive microwaves from one or more microwave sources. The antenna units convert these signals into plane wave microwaves that are incident on the targeted subject. The plane waves are not phase/frequency correlated, so they do not produce substantial constructive interference that would cause localized heating. Thus a pseudo uniform microwave field can be generated. In use, the device may include a temperature monitoring subsystem and a control system, wherein the control system uses temperature information from the temperature monitoring subsystem to adjust the output power of each antenna unit as needed to heat the whole body or a region of the body as needed. The energy delivered into the body is redistributed by blood circulation to facilitate rapid heating for whole-body hyperthermia treatments. Electronic scanning can be used to adjust the power output and distribution based on input from the temperature monitoring subsystem, and can also be used to provide localized heating for a regional hyperthermia treatment, e.g., by selectively heating an area, region or limb, such as one where a tumor is located. In addition, unlike an infrared treatment method, the invention can be used without enclosing the subject in a chamber, so it is easier to permit air circulation to cool the subject's skin, further reducing the risk of injury and promoting the comfort and safety of the treated subject, who would not require. prolonged or deep anesthesia during treatment. [0046] In another aspect, the invention provides a microwave diathermy device for heating a lossy or conducting medium, which device comprises: a) an array of antennas, and b) means to generate a plurality of microwaves that are not correlated in frequency; wherein each of the plurality of microwaves is directed to at least one of the antennas. The means for generating a plurality of microwaves may be a single microwave generating source whose output is then split by a splitter into a multiplicity of separated microwaves that are directed to individual antenna units in the antenna array; wherein at least some of the separated microwaves are modified in frequency before the signals reach the antennas, so that the microwaves output by some of the antennas are not correlated in frequency. In other embodiments, the means for generating a plurality of microwaves comprises two or more microwave sources that generate microwaves that are not frequency correlated; the outputs of these microwave sources may be further split as needed to provide a suitable number of microwaves to feed each antenna unit in the array so that the outputs from the antenna units are non-interfering microwaves. The device may utilize a combination of means, e.g. microwaves that are not frequency correlated, or that are not phase correlated, or both, to provide a pseudo- uniform field of non-interfering microwaves. In many embodiments, the antenna arrays receive microwaves from the microwave source(s) and outputs spherical microwaves, which the antenna units then convert into plane waves that are radiated by the antenna units and are incident upon a subject to be treated with hyperthermia.

Brief Description of the Drawings

[0047] The Figures describe various features of the present invention, including the following features:

(1) Computer based real time control subsystem,

(2) Non-interference microwave source,

(3) Antenna array,

(4) Heated lossy medium.

(5) Temperature monitoring subsystem.

(6) Heart rate monitor and blood pressure monitor.

(7) Software package.

(8) Computer. (9) Computer peripheral circuit.

(10) Microwave radiator.

(11) Converter that converts the non-planar microwave to planar microwave.

(12) Conventional microwave source

(13) Random delay timer with less than 0.1ns delay time

(14) Antenna units.

(15) Pseudo uniform microwave electromagnetic fields.

(16) Reflective structure with parabolic cross-section..

[0048]

[0049] FIG. 1 is a block diagram illustrating a microwave heating apparatus of the present invention, which is generally similar to one described in Example 3.

[0050] FIG. 2 is an illustration of one of the preferred embodiment of the non-interfering microwave source.

[0051] FIG. 3 is a depiction of an embodiment of the reflective converter that converts the spherical or cylindrical microwave to substantially planar microwave.

FIG. 4 is a block diagram of a preferred embodiment of the antenna array in the microwave heating apparatus of the present invention FIG. 5 is a block diagram of a computer based control system.

Detailed Description

[0052] The devices and methods of the invention use pseudo uniform microwave field to heat an object or medium, which may be a lossy medium or a conducting medium. An example of a lossy medium is one having a substantial water content, since water absorbs microwave radiation relatively well. Notably, however, microwave radiation can penetrate into a water- containing object by at least a few centimeters, allowing the microwave energy to be absorbed within the object, while shorter and longer wavelengths would be either absorbed entirely at the surface of the object or transmitted through the object without efficient absorption.

[0053] The term "whole-body" as used herein means heating the human body, including the limbs to a temperature above its normal homeostatic temperature. Because heat is redistributed by conduction and by the circulating blood, whole body hyperthermia can be achieved without covering every square inch of the subject's body with microwave radiation, but it typically involves administering microwave heating to at least a majority of one aspect of the subject's body.

[0054] 'One aspect' of the body as used herein refers to, for example, the front or back of the body, or one side of the body. The methods and devices described herein operate successfully by delivering microwaves to one aspect or to more than one aspect of the body; thus, for example, an array of microwave antennas in a substantially flat frame could be • positioned above a person's prostrate body, and would deliver microwaves to the front of the body only. This is quite sufficient to heat the entire body of the subject, because other mechanisms redistribute the heat energy as it builds up in the areas where microwaves are absorbed. Alternatively, an array of antennas could be held in one or more frames so that the array is curved or contoured to partially surround a person's body, and could, for example, deliver microwaves to the front and sides of a person's prostrate body. In other embodiments, the person could be standing upright or could be seated, and one or more antenna array could surround most of the person's body.

[0055] In some embodiments, the antenna units are held in position by a support or a frame that is adapted to permit movement of the antenna units. The frame may be adapted to allow the user to change the spacing and/or relative orientation of one or more, and optionally of each of the antenna units. The frame may also be adapted to allow the antenna units to be tilted relative to the plane of the frame, or relative to the orientation of other antenna units. In such embodiments, each of the antenna units may conveniently be positioned to direct its output to a desired location or in a desired direction. This permits the antenna array to be adjusted so it will conform more precisely to the body of a subject to be treated for whole-body hyperthermia, and it alsq permits the antenna array to be adjusted more precisely for providing local or regional hyperthermia treatments.

[0056] The term "control system" refers to a computer based real time control system. It can consists of one or more computers (for example, the computer may be one or more microprocessors or microcontrollers, or it may be a computer network , personal computer, etc.), one or more display devices or terminals, user input devices such as key board, mouse, or touch screen; and computer peripherals for control and sampling purpose. The computer based control sub-system can also have the networking connection to access local area network or wide area network for remote access. The computer based real-time control sub-system takes the user inputs from the input device, sets the selected operating mode. According to selected operating mode, it can run through an algorithms and produce one or more control signals to modulate the output of one or more antenna units or of the non-interfering microwave source(s). Thus it controls and adjusts the output power of the non-interfering microwave source and/or the output of individual antennas and consequently changes the distribution of the power density of the electromagnetic field and hence adjusts the temperature of the diathermized position in the medium inside the electromagnetic field.

[0057] The term "electronic scan" as used herein refers to the following process: using a temperature monitoring subsystem having one or more temperature sensors either in contact or non-contact with the object to be heated, to measure the temperatures at different parts of the object such as a human body; sending temperature information from the sensors of the temperature monitoring subsystem to a control system, such as a computer based real-time control system; and having the control system use the temperature information to modify the microwave energy being delivered to the object by the array of plane- wave radiators. The control system processes the temperature information it receives to determine what the temperature distribution inside the targeted object appears to be, and compares that to a desired temperature distribution. For example, in a whole-body hyperthermia treatment, the control system could be programmed to achieve a particular uniform target temperature, such as 43⁰C, throughout the targeted object. The control system would then calculate a control signal for one or more of the antenna units in the antenna array, which often controls each antenna unit separately. The control signal would adjust the power density and/or the distribution of the power density produced by the antenna array, in order to increases the rate of heating in 'cool' spots in the targeted object and it could stop heating areas that have achieved or exceeded their target temperature by turning the power down or off for antennas that most directly deliver microwaves to those areas.

[0058] The devices and methods use at least one microwave source to power an array of antenna units. One microwave source is sufficient, provided it has multiple output ports or its output can be split to provide multiple output ports, so that there are enough outputs to feed a microwave to each antenna unit. However, multiple microwave sources can be used, and can be adapted or controlled to provide non-interfering microwaves. The microwaves that are output from one or more microwave sources can be modified to be non-interfering at any point prior to their emission from the antenna unit as non-interfering plane waves.

[0059] The array of antenna units can be of any shape or arrangement to fit different needs. For example, a relatively flat frame or support structure may be used to support and position the antenna units. A frame that is contoured to wrap partially around a person's body can be used for a device specifically adapted for whole-body hyperthermia. In some embodiments, the frame is flexible and permits the user to adjust to some degree the shape of the array of antennas so that it fits each object or each patient. Alternatively, the frame may comprise two or more panels, which may be separate or may be connected together such as by a hinge to permit the panels to be adjusted. Illustrative examples are shown in Figure 2.

[0060] The size of the array can be any that is suitable for the particular application, and is determined partly by the size and spacing of the antenna units. In some embodiments, the array is at least about three square feet in area, so it can be used to apply plane microwaves to an object of about that size. In other embodiments, the array is at least about five square feet in area. In some embodiments, the antenna array is at least about four feet in its longest dimension so it can be used to apply microwave energy over the majority of the body of an adult person. The array comprises a plurality of antenna units, and can include four or more antenna units, or ten or more antenna units. In some embodiments, it includes 8 or more, and optionally 16-32 or more antenna units. The antenna units may be 5-10 or 10-15 or 15-20 cm in their major dimensions, or they may be larger or smaller when consistent with their function. They may be symmetric, e.g. square, rectangular or circular in shape, or they may be irregular in shape. They may be placed close together (e.g., each may be less than 2 cm from its nearest neighbor), or they may be spaced further apart. In some embodiments, their spacing is described according to the distance between the center point of the face of each antenna unit, and that spacing may be about 5 cm or about 10 cm or about 15 cm or about 20 cm, or it may be 25 cm or more.

[0061] The principle method of the present invention includes use of an antenna array to transform multiple microwaves into approximate plane waves, to form a pseudo uniform electromagnetic field which surround and impinge upon a human body. The plane microwaves are directed toward and incident upon at least one aspect of a person's body to induce hyperthermia. The microwaves can penetrate through skin and fat, and further penetrate 2-3 cm into the muscle tissue, to directly heat the muscle and blood. Because the multiple non- interfering microwaves are not correlated in phase, or they are not correlated in frequency, or both, they will not cause interference with each other after radiating from the antenna units; the superimposed microwaves thus form a pseudo uniform electromagnetic field incident upon and/or surrounding the human body when all of the units are operating, so no over-heated spot will be produced during the initial phase of heating, yet the thermal energy can penetrate deeply into the human body, greatly reducing the time to raise a patient's body temperature to the target temperature required by the treatment. The patient's circulating blood helps transfer heat to the whole-body to ensure the subject's temperature rises rapidly throughout the whole body.

[0062] Another method of the present invention is to use electronic scanning to operate outside of the pseudo uniform field method. While the device can achieve substantially uniform energy delivery over the entire body of a subject, in many applications that is not all that is required. For example, when heating a person's body, microwave energy will be absorbed with different efficiencies in different portions of the body, and the heat produced will be redistributed at different rates in different tissues. Thus even though the energy field applied is uniform, the resulting changes in temperature in the subject's body will not be. Rather, some areas will heat more quickly and others more slowly. Accordingly, the device and methods of the invention provide a control system that can individually control each antenna in the array, preferably using a continuously variable power control mechanism. The control system can adjust the power density and power distribution from each antenna unit to provide even heating throughout the body if desired, or it can be programmed to form a heating center. The heating center is usually the place where a tumor is located, and the device can be used to produce higher temperature inside the tumor than in the surrounding regions by adjusting the power of the antenna units to maximize delivery of microwave energy to the affected tissue or region. Such method can be used to perform deep local or regional hyperthermia, using the same device that is also well suited to provide whole-body hyperthermia treatment.

[0063] The pseudo uniform electromagnetic field of the invention is not perfectly uniform, due to practical limitations; however, the use of plane waves provides much more uniform heating than devices using a spherical microwave source or sources. Thus some aspects of the invention employ a generally planar microwave, which is known in the art as distinct in characteristics from a 'spherical' wave, eve if it is not entirely planar. This plane waves provide a more even thermal energy delivery method than a device using a spherical microwave, because spherical microwaves deliver most of their energy into a relatively small area, creating local 'hot spots' in the targeted object. Even the use of multiple spherical wave sources produces localized 'hot spots' in the region nearest each radiator. An array of planar wave radiators, by comparison, provides a more nearly uniform energy distribution over a relatively large surface, such as a human body. The devices and methods of the invention employ an array of antennas to create a 'patchwork' of plane microwaves that can, in certain embodiments, effectively cover at least the majority of one aspect of a targeted object, such as one aspect of a human body. [0064] The pseudo uniform electromagnetic field produced by the array of antennas is distributed in a relatively large volume that includes at least part of a targeted object. The power density of such field in a unit area is much smaller than that produced by a single antenna would be, assuming both are using the same amount of total power to perform hyperthermia. However, because it delivers energy over a larger area, and indeed a larger volume, of the targeted object, it can introduce more thermal energy overall than a single higher-powered antenna, and it can do so without focusing that energy into a small volume, which would cause injury to a human subject, for example. Plus, no enclosed treatment chamber is needed using the present invention, since heat is delivered into the subject rather than just onto the surface of the subject; this allows the air at about normal ambient temperature, or even cooled air, to naturally cool down the patient's skin. This improves patient comfort in hyperthermia treatments, because the skin is where the greatest perception of pain may occur, and where the patient's body has fewer methods for reducing the build-up of heat, i.e., while internal tissue has greater blood flow and is surrounded by other water-laden material that can help redistribute heat that begins to build up, the skin has only air on one side and has a relatively low blood flow, and at the same time it has many pain sensors; thus avoiding heat build-up at the skin is a critical factor in avoiding discomfort and injury. As a result of the relatively even heat distribution and the delivery of energy into the tissue rather than just onto the surface of the skin as an IR heater would do, the patient using the present invention's methods and devices feels comfortable and does not need to be deeply sedated. More importantly, the methods and devices described herein greatly reduce the risks involved with longer heating time required by IR technologies, and they do not burn the skin of the patient as IR devices can, thus the invention overcomes many of the shortcomings of previous technology.

[0065] In one aspect, the invention provides a microwave diathermy device for heating a human subject's body, which device comprises: at least one microwave source; a multiplicity of microwave output ports, wherein each output port is operatively connected to receive microwaves from a microwave source and to output microwaves to an antenna unit; a plurality of microwave radiating antenna units; wherein each antenna unit is operatively connected to receive microwaves from one of said output ports, and each antenna unit comprises a radiator to produce a spherical microwave, and a converter to convert the spherical microwave into a plane wave; wherein the output of each antenna unit is non-interfering with respect to the output of other antenna units.

[0066] Optionally, the device further comprises a temperature monitoring subsystem and a control system that receives input from the temperature monitoring subsystem, wherein the control system is adapted to adjust the power output of one or more of the antenna units in response to input from the temperature monitoring subsystem.

[0067] Typically, the antenna units are oriented to direct the pseudo planar microwaves they produce toward a surface of a targeted object to be heated, e.g., toward one aspect of the body of a subject to be treated via hyperthermia.

[0068] The devices may thus be sized to provide a substantially uniform field of plane microwaves over the majority of one aspect of a human subject's body. For example, it may be sized to produce a pseudo uniform microwave field over an area of about three square feet. It may also be sized so that its longest dimension is at least three feet long, or at least four feet long. Alternatively, the devices can be sized to perform localized hyperthermia using the method in this invention, so it can be sized to much smaller dimensions.

[0069] The devices of the invention may have an adjustable or continuously adjustable output power and operate at a single operating frequency or multiple operating frequencies, such as at least one frequency between about 0.1 GHz and 20 GHz. In some embodiments, the apparatus includes at least one microwave source that provides microwaves in the 2000 MHz to 3000 MHz frequency range. Optionally, more than one microwave source can be used. In a preferred embodiment, at least one microwave source provides microwaves at a frequency of about 2450 MHz.

[0070] In certain embodiments, more than one microwave source is used, and the sources used to produce microwaves are not correlated in frequencies. The microwave frequency of a signal may also be changed by a frequency modulator that shifts the frequency of one output from a microwave source as the microwave is en route to an antenna of an antenna unit, so that it radiates at a frequency that is not correlated with the frequency produced by the microwave source. Alternatively, a frequency modulator may be used to vary the frequency of a signal during operation so that the frequency of the microwave that it produces is not correlated with the frequency of microwaves that overlap with it in operation. Additionally, the frequency of the microwaves from any microwave source may be varied during operation by use of an adjustable frequency output or by use of a filter element that modifies the frequency or varies the frequency of microwaves passed through it so that the frequency of the microwave is not correlated with other microwaves in the field. .

[0071] The antenna unit includes a radiator that produces a spherical wave, and a converter to convert this spherical wave into a plane wave. In some embodiments, the converter operates by refractive principles, and uses a refractive element that comprises a dielectric material with a refractive index of 1.2 to 1.3, such as 1.23. In other embodiments, a reflective converter is used to produce the plane microwave used by the invention.

[0072] In certain embodiments, the array of antenna units comprises at least four antenna units, and the control system is adapted to individually control the output power of each antenna unit. In some such embodiments, the device further comprises one or more temperature sensors adapted to be either in contact or non-contact with the targeted object while the device is in use.

[0073] In addition to the antenna units and microwave source that are used to provide non- interfering plane microwaves, the apparatus of the invention optionally includes a heart rate monitor. In some embodiments, at least a portion of the heart rate monitor is adapted for use in the microwave field, and a monitor that resists interference or damage from microwaves is preferred. In preferred embodiments, the apparatus includes at least two heart rate monitors to provide a redundant system for the safety of the hyperthermia-treated subject. In some embodiments, the heart rate monitors include at least a portion that is adapted to shield the portion of the heart rate monitor from interference caused by the microwave field, so the portion can be placed within the microwave field during operation. This facilitates monitoring the condition of the subject during hyperthermia treatment without interrupting the treatment or exposing a health care provider to the microwave field. The heart rate monitor can be adapted for placement at least partially within the microwave field by connecting the heart rate monitor to a low-pass filter circuit at a low-pass frequency of less than 10 Hz, and further connecting it to an ultra-low frequency amplifier circuit. Each of these circuits is preferably shielded to improve its resistance to microwave interference.

[0074] The apparatus of the invention can also include an optional blood pressure monitor to track the status of a subject undergoing hyperthermia. In some embodiments, at least a portion of the blood pressure monitor is adapted for use in the microwave field, and a monitor that resists interference or damage from microwaves is preferred. In some embodiments, the apparatus includes at least two blood pressure monitors to provide a redundant system for the safety of the hyperthermia-treated subject. In some embodiments, the heart rate monitors include at least a portion that is adapted to shield the portion of the blood pressure monitor from interference caused by the microwave field, so the portion can be placed within the microwave field during operation. This facilitates monitoring the condition of the subject during hyperthermia treatment without interrupting the treatment or exposing a health care provider to the microwave field.

[0075] The invention also provides hyperthermia treatment methods, such as a method to establish a desired temperature distribution in a targeted lossy or conducting object by heating at least a portion of the object, which method comprises: providing a microwave source (or sources) that is adapted to deliver microwaves to an array of antenna units, providing an array or multiple arrays of microwave antenna units, wherein each antenna unit produces a substantially plane microwave and the power output of each antenna unit can be adjusted by a control system; wherein the substantially planar microwaves radiated by the individual antenna units are not phase correlated, or that are not frequency correlated, or both with overlapping microwaves radiated by other antenna units; providing a plurality of temperature sensors, wherein each temperature sensor communicates to the control system the temperature at a region within the targeted object; applying plane microwaves to the targeted object using the array of microwave antenna units, wherein the plane microwaves are non-interfering; thus forming a pseudo uniform microwave electromagnetic field around the heated object; and adjusting the power output of the antenna units in response to information from the temperature sensors to achieve the desired temperature distribution in the targeted lossy object.

[0076] In another aspect, the invention provides a method to use microwave energy to elevate the temperature of a subject's body for a hyperthermia treatment, where the method is characterized by use of substantially plane microwaves delivered by an array of antenna units that direct the microwaves onto a majority of one aspect of the subject's body, wherein the microwaves that are not correlated in phase, or that are not correlated in frequency, or both where they overlap. In these methods, a plurality of temperature sensors can be used to measure the temperature of the subject's body at different points, and the temperature measurements may be used to adjust the power output of antenna units in the array of antenna units in order to produce a desired temperature distribution within the subject's body.

[0077] The methods of the invention are sometimes used for treating a subject with a cancer that is widespread or delocalized, or one that has metastasized. This treatment includes elevating the temperature of the subject's body to increase the effectiveness of a cancer treatment such as chemotherapy or radiation therapy.

[0078] The following examples are illustrative of some preferred embodiments only, and are not intended to limit the scope of the invention.

Example 1

[0079] In one embodiment of the microwave heating method for whole-body or regional heating, the invention uses non-interfering microwave sources to output 24 microwaves that are not correlated in frequency; then it sends the 24 microwaves to corresponding antenna units in the antenna array to form a pseudo uniform microwave electromagnetic field. A patient is introduced into this field,, which surrounds and penetrates the patient's body to elevate the patient's body temperature for a hyperthermia treatment. Each of the antennas is positioned to deliver energy to a particular region of the patient's body, so that the majority of the patient's body is covered by microwaves from one of the antennas, and there is minimal overlap of the areas covered by the individual antenna units in the array of antennas. While the electromagnetic radiation heats the patient's body, electronic scanning technology is used to adjust both the power density and the distribution of the power in the electromagnetic field by turning each of the antenna units up, down, or off, as required.

[0080] Determining which antenna units to turn up or down is done by a control system. The control system collects temperature information from one or more locations in or on the treated subject, and compares it to a desired temperature or temperature distribution set by the user, such as a uniform temperature target of 42⁰C, or a similar suitable hyperthermia temperature level. The temperature information about the treated subject may be collected by any conventional means, but in a preferred embodiment, that information is collected by a plurality of temperature sensors on or in the subject's body. In this example, the device includes 24 temperature sensors, one of which is positioned in the region of the patient's body that is directly irradiated by each of the 24 antennas, so each antenna is associated with a particular temperature sensor. The control system then correlates the temperature information from the sensors to determine whether each antenna needs to have its power turned up or down. [0081] This electronic scanning continues until the desired temperature distribution within the patient's body is achieved. The controlled microwave heat delivery is then continued for the desired therapeutic time period, which can be selected by a user of the device. During the hyperthermia treatment, the subject's blood pressure and / or heart rate may be monitored to track the patient's condition or reactions to the hyperthermia process. The monitor(s) used for such monitoring may be adapted for use in the system; for example, the portion of the monitor that is exposed to microwave fields during use can be shielded so that the microwaves do not interfere with its operation. Selection of the temperature target and the time duration of the treatment are well within the art, based on extensive literature regarding hyperthermia treatments, and depend upon the age and condition of the patient and on what type of therapy (e.g., chemotherapy or radiation therapy) the hyperthermia treatment is being used to enhance.

Example 2

[0082] An exemplary device of the invention is depicted schematically in the Figures. As shown in Figure 1, the apparatus consists of an antenna array (1), at least one source of non-interfering microwaves (2), a computer based real-time control system (3) and a temperature monitoring subsystem (4), preferably including a plurality of temperature sensors that are suitable for use within the heated zone of the targeted object. The antenna array (1) is mounted in a frame as shown in figure 2 and consists of, for example, 16 antenna units (5), each antenna unit comprising a microwave radiator (6) and a converter (7) that converts the spherical microwave to a plane microwave. The microwave source (2) has, e.g., 16 output ports that output 16 microwaves which are non-correlated in frequency. In some embodiments, frequency correlation is avoided by applying a random frequency adjustment to one or more of the microwaves before it reaches the radiating antenna. The microwave source (2) has a continuously adjustable output power range of 0-3 kW and an output frequency in the range of 0.5-10 GHz. Preferably, the frequency is adjustable by the user. In one embodiment, the frequency is between 2 and 3 GHz, and can be 2.45 GHz.

[0083] Each output port of or connected to the non-interfering microwave source is connected to an input for a corresponding microwave antenna unit in the antenna array; each antenna unit includes a radiator and a converter. The radiator produces a spherical microwave, which then passes through the converter. The converter transforms the spherical microwave into a plane microwave. The converter in the antenna unit is made using a functional material that is synthetic and is a dielectric material with a refractive index of 1.23 (the refractive index of the functional material of the converter is >1, and the optimal value of the refraction index of the converter is within the range of 1.2 - 1.3). Methods for making suitable converters are known in the art.

[0084] The computer based real time control system adjusts both the output power of the microwave source and the distribution of power density of the microwave field based on the inputs it receives from the temperature monitoring subsystem. Electronic scanning can be used to perform whole-body heating, and it can be used to provide a non-uniform output when the temperature distribution indicates that non-uniform heating is needed to achieve the desired temperature distribution in the targeted object. The control system can be programmed to adjust the output of each antenna unit in the array to achieve the desired temperature distribution within the targeted object, which can be a uniform temperature for whole-body hyperthermia, or it can be non-uniform, in which case the control system can be programmed to adjust the power density and power distribution to form a heating center - for deep regional or local hyperthermia. In an exemplary embodiment, the temperature monitoring subsystem (4) has 6 sensors that are accurate to within ± 0.1 ⁰C.

[0085] When the microwave heating apparatus and method of the present invention are used to treat a cancer patient, the patient will only feel warm in the irradiated parts of the body, without experiencing hot-spots that would cause injury, and minimal uncomfortable sensations or side effects will be experienced. The microwave heating apparatus using a pseudo uniform electromagnetic field and electronic scanning based on multiple temperature sensors in or on a patient's body is safe, reliable, and easy to operate.

Example 3

[0086] An antenna support frame is constructed in the form of a rectangle at least about four feet long in a first dimension, and having a parabolic curvature transverse to the first dimension. Figure 3 provides a diagram of this arrangement. At least two and preferably four or more antenna units are placed at approximately equal spacing along the line that formed by the focal points of the parabolic cross sections of the frame. The frame is made of material that reflects microwaves. Each antenna unit produces a spherical microwave, or a cylindrical microwave whose axis is approximately aligned with the line formed by the focal points of the parabolic shape of the frame, and , the parabolic curvature of the frame is sized and shaped to convert microwaves from the antenna units to produce a reflected plane microwave. A subject to be treated is placed below the antenna units so that the plane microwave is incident upon one aspect of the subject's body. The antenna units are adapted so that each antenna unit produces non- interfering microwaves, that are not correlated in phase, and the adjacent units are placed at a distance that allows the microwave fields to overlap only in regions where the microwave energy field strength is less than about 50% of the maximum strength of the field from one antenna unit, which ensures that the overlapping regions of the microwave field do not exceed the energy input density maximum for a single antenna unit. The system further includes a temperature measuring system having a temperature sensor associated with each antenna unit, wherein each temperature sensor is directed to a portion of the subject's body near the center of the surface area of the subject's body that is covered by the microwave field from the antenna unit associated with that sensor.

[0087] A similar device can be constructed in a generally cylindrical form having an elliptical cross section, and having a series of at least two antenna units positioned along and parallel to the line corresponding to each focal point forming the elliptical cross section. The elliptical device may be sized to surround a human subject for whole-body treatment, or it may be sized to surround a portion of the body such as one limb.

The same concept can be applied to surround an antenna array with a housing having an inner surface of a microwave-reflective material and shaped in a generally cylindrical form having an elliptical cross-section. In that design, the antenna units are positioned along a line formed by the focal points of the elliptical cross-section, so that the microwaves from the antenna units are reflected from the inner reflective surface of the housing to form a plane microwave. The reflected plane microwave is used to heat the medium or object to be heated.

[0088] Although the present invention has been explained above by way of a preferred embodiment thereof, it should be pointed out that any modifications apparent to the skilled user are included in the invention, and these preferred embodiments do not limit the scope of the invention.

Claims

1. A microwave diathermy device for heating a lossy or conducting medium, said device comprising: a) at least one microwave source that provides microwaves through a multiplicity of microwave output ports, wherein each output port is operatively connected to deliver microwaves to an antenna unit; and b) a plurality of microwave radiating antenna units; wherein, each antenna unit comprises a radiator to produce a non-planar microwave, and a converter to convert the non-planar microwave into a substantially plane microwave, wherein the frequency of the microwave output of any antenna unit is not correlated in frequency with the frequency of the microwave output of the other antenna unit whose microwave field overlaps with the microwave field from the first antenna unit.

2. The device of claim 1 , which further comprises a temperature monitoring subsystem and a computer based control system that receives input from the temperature monitoring subsystem, wherein the computer based control system is adapted to adjust the power output of one or more of the antenna units in response to input from the temperature monitoring subsystem; and wherein the temperature monitoring subsystem is adapted to measure a temperature of at least one portion of the medium while the device is in use.

3. The device of claim 1, wherein at least one microwave source produces multiple non-interfering microwaves that are not correlated in frequencies;

or at least one microwave source produces a single microwave that is split into multiple output microwaves, and the frequency of at least one microwave signal is modified before that microwave is radiated from an antenna unit;

or at least one microwave source produces a single microwave that is split into multiple output microwaves, and the phase of at least one microwave signal is modified before that microwave is radiated from an antenna unit.

4. The device of claim 1 , wherein the antenna units are oriented to direct the substantially plane microwaves toward a surface of a targeted object to be heated; wherein the antenna array is configured to provide a pseudo uniform field of microwaves over the majority of one aspect of a lossy medium to be heated.

5. The device of claim 1 , wherein at least one microwave source has a continuously adjustable output power and at least one microwave source has an operating frequency between about 0.1 GHz and 20 GHz.

6. The device of claim 1, wherein the microwave source produces microwaves having a frequency between 0.5 GHz and 3 GHz.

7. The device of claim 1, wherein the functional element of the converter comprises either a reflective element that converts a spherical microwave to a substantially planar microwave, or a refractive element comprising a natural or synthetic dielectric material with a refractive index greater than 1 (no>l) .

8. The device of claim 1 , wherein the array of antenna units is configured to produce a pseudo uniform microwave field that is sized to be used for whole-body hyperthermia.

9. The device of claim 8, wherein the array of antenna units comprises at least four antenna units, and the computer based control system is adapted to control the output power of each antenna unit.

10. The device of claim 9, which further comprises a temperature monitoring subsystem that provides a temperature sensor associated with each antenna unit, and said device further comprises a computer-based controller that is adapted to adjust the output of each antenna unit to achieve a desired temperature distribution in the medium.

11. The device of claim 9, which comprises at least two redundant temperature monitoring sensors adapted to measure the temperature of the subject at one region near the heating center.

12. The device of claim 9, wherein the temperature monitoring sub-system comprises a multiplicity of temperature sensors.

13. The device of claim 9, wherein the antenna units are held in place by a support structure that permits the position and/or angle of at least one of the antenna units to be adjusted.

14. The device of claim 9, comprising at least one heart rate monitor and/or at least one blood pressure monitor, at least a portion of which is adapted to be placed within the microwave field, such that the heart rate monitor or blood pressure monitor resists the interference of the microwave field.

15. The device of claim 9, wherein the heart rate monitor is adapted for placement at least partially within the microwave field by connecting the heart rate sensor to a low- pass filter circuit at a low-pass frequency of less than 10 Hz, and further connecting it to an ultra-low frequency amplifier circuit.

16. The device of claim 9, wherein a microwave-reflective material is disposed behind or around the antenna units.

17. The device of claim 16, wherein the microwave reflective material is formed into a shape that converts non-planar microwaves from at least one antenna unit into a plane wave.

18. A method to establish a desired temperature distribution in the body of a subject by forming a pseudo uniform microwave field to heat at least a portion of the subject's body, which method comprises:

providing a microwave source that produces non-interfering microwaves that are not frequency correlated; providing at least one array of microwave antenna units, wherein each antenna unit receives microwaves from the microwave source and produces a substantially plane microwave, wherein the power output of each antenna unit can be adjusted by a computer based control system using electronic scanning; providing a temperature monitoring sub-system adapted to measure the temperature of at least one portion of the subject, wherein the temperature monitoring subsystem provides temperature information to the computer based control system; providing at least one heart rate monitor and/or at least one blood pressure monitor, at least a portion of which is adapted to be placed within the microwave field, such that the heart rate monitor or blood pressure monitor resists the interference of the microwave field; positioning the antenna array to deliver the substantially plane microwaves to form a pseudo uniform microwave electromagnetic field incident upon the subject to be heated; adjusting the power output of the antenna units in response to information from the temperature monitoring sub-system to achieve the desired temperature distribution in the targeted object; and

monitoring the subject's heart rate and/or blood pressure during a hyperthermia treatment.

19. The method of claim 18, wherein the power output of the antenna units is adjusted to produce a pseudo uniform microwave electromagnetic for substantially uniform heating of the subject.

20. The method of claim 18, wherein the power output of the antenna units is adjusted to form a heating center for regional hyperthermia treatment of the subject.

21. The method of claim 20, wherein at least two redundant temperature monitoring sensors are used to measure the temperature of the subject at one single point near the heating center. Wherein the temperature at multiple point of the subject are monitored.

22. A method to use microwave energy to elevate the temperature of a subject's body, characterized by use of substantially planar microwaves delivered by an array of antenna units that direct the microwaves onto a majority of one aspect of the subject's body, wherein the microwaves are not correlated in frequency.

23. The method of claim 22, wherein a plurality of temperature sensors is used to measure the temperature of the subject's body at different points.

24. The method of claim 23, wherein the temperature measured at different points of the subject's body is used to adjust the power output of antenna units in the array of antenna units in order to produce a desired temperature distribution within the subject's body.

25. The method of claim 24, wherein the substantially planar microwaves have a frequency in the range of about 0.1 GHz to about 20 GHz, and the frequencies of the substantially planar microwaves are not frequency correlated

26. The method of claim 22, wherein at least one heart rate monitor and/or at least one blood pressure monitor, at least a portion of which is adapted to be placed within the microwave field, is used to monitor the subject while the subject's temperature is elevated by heating with microwave energy. .

27. The method of claim 22, wherein elevating the temperature of a subject's body is used to increase the effectiveness of a cancer treatment selected from chemotherapy and radiation therapy.

28. The method of claim 24, wherein the subject has a cancer that is widespread or has metastasized.

29. A microwave diathermy device for heating a lossy medium, said device comprising: a) an array of antennas, and b) means to generate a plurality of microwaves that are not correlated in frequency, and the said microwaves have an operating frequency between about 0.1 GHz and 20 GHz.;

30. The device of claim 29, wherein the means to generate a plurality of microwaves comprises two or more microwave sources that are adapted to produce microwaves that are not correlated in phase, or that are not correlated in frequency, or both.

31. The device of claim 29, wherein the means to generate a plurality of microwaves comprises a microwave energy source, a splitter to divide the output of the microwave energy source into a multiplicity of separated microwaves, and a frequency modulating device to shift the frequency of at least one of the separated microwaves; wherein each of the separated microwaves is delivered to a different antenna.

32. The device of claim 29, wherein the microwave output from each of the antennas is converted by a converter into a plane microwave.

33. The device of claim 32, wherein the device is adapted to prevent interference between the microwave outputs that overlap with one another.

34. A microwave source that provides a multiplicity of non-interfering microwaves, which comprises a source of microwave energy, a splitter to separate the microwave energy into a multiplicity of separate microwaves, and a frequency modulator that changes the frequencies of at least one of the microwaves so that at least two of the separate microwaves are not frequency correlated.

35. A microwave source that provides a multiplicity of non-interfering microwaves, which comprises at least one source of microwave energy, a splitter to separate the microwave energy into a multiplicity of separate microwaves, and a phase modulator that changes the phases of at least one of the microwaves so that at least two of the separate microwaves are not phase correlated.