CA2191312A1 - Microwave tomographic spectroscopy system and method - Google Patents
Microwave tomographic spectroscopy system and methodInfo
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- CA2191312A1 CA2191312A1 CA002191312A CA2191312A CA2191312A1 CA 2191312 A1 CA2191312 A1 CA 2191312A1 CA 002191312 A CA002191312 A CA 002191312A CA 2191312 A CA2191312 A CA 2191312A CA 2191312 A1 CA2191312 A1 CA 2191312A1
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Classifications
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- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
- A61B5/00—Measuring for diagnostic purposes; Identification of persons
- A61B5/05—Detecting, measuring or recording for diagnosis by means of electric currents or magnetic fields; Measuring using microwaves or radio waves
- A61B5/0507—Detecting, measuring or recording for diagnosis by means of electric currents or magnetic fields; Measuring using microwaves or radio waves using microwaves or terahertz waves
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- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
- A61B18/00—Surgical instruments, devices or methods for transferring non-mechanical forms of energy to or from the body
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- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
- A61B18/00—Surgical instruments, devices or methods for transferring non-mechanical forms of energy to or from the body
- A61B18/18—Surgical instruments, devices or methods for transferring non-mechanical forms of energy to or from the body by applying electromagnetic radiation, e.g. microwaves
- A61B18/1815—Surgical instruments, devices or methods for transferring non-mechanical forms of energy to or from the body by applying electromagnetic radiation, e.g. microwaves using microwaves
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- A—HUMAN NECESSITIES
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N22/00—Investigating or analysing materials by the use of microwaves or radio waves, i.e. electromagnetic waves with a wavelength of one millimetre or more
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- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
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- A61B17/00—Surgical instruments, devices or methods, e.g. tourniquets
- A61B17/00234—Surgical instruments, devices or methods, e.g. tourniquets for minimally invasive surgery
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- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
- A61B18/00—Surgical instruments, devices or methods for transferring non-mechanical forms of energy to or from the body
- A61B18/04—Surgical instruments, devices or methods for transferring non-mechanical forms of energy to or from the body by heating
- A61B18/12—Surgical instruments, devices or methods for transferring non-mechanical forms of energy to or from the body by heating by passing a current through the tissue to be heated, e.g. high-frequency current
- A61B18/14—Probes or electrodes therefor
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- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
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- A61B18/00—Surgical instruments, devices or methods for transferring non-mechanical forms of energy to or from the body
- A61B18/18—Surgical instruments, devices or methods for transferring non-mechanical forms of energy to or from the body by applying electromagnetic radiation, e.g. microwaves
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- A—HUMAN NECESSITIES
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- A61B18/00—Surgical instruments, devices or methods for transferring non-mechanical forms of energy to or from the body
- A61B18/18—Surgical instruments, devices or methods for transferring non-mechanical forms of energy to or from the body by applying electromagnetic radiation, e.g. microwaves
- A61B18/20—Surgical instruments, devices or methods for transferring non-mechanical forms of energy to or from the body by applying electromagnetic radiation, e.g. microwaves using laser
- A61B18/22—Surgical instruments, devices or methods for transferring non-mechanical forms of energy to or from the body by applying electromagnetic radiation, e.g. microwaves using laser the beam being directed along or through a flexible conduit, e.g. an optical fibre; Couplings or hand-pieces therefor
- A61B18/24—Surgical instruments, devices or methods for transferring non-mechanical forms of energy to or from the body by applying electromagnetic radiation, e.g. microwaves using laser the beam being directed along or through a flexible conduit, e.g. an optical fibre; Couplings or hand-pieces therefor with a catheter
Abstract
The invention is a system for non-invasive microwave tomographic spectroscopy of tissue using a plurality of microwave emitter/receivers (16) spatially oriented to the tissue, an interface medium (106) placed between the emitter/receivers (16), a control subsystem (65) operably coupled to the plurality of microwave emitter/receivers (16) for selectively controlling power to the plurality of emitter/receivers (16) for receiving microwave signals from the plurality of emitter/receivers (16) so that multiple frequency microwave radiation is emitted from a selected plurality of emitter/receivers (16) and received by a selected plurality of emitter/receivers (16) after interacting with and passing through the tissue (135), and a computational subsystem (77) operably connected to the control subsystem (65) for computing a tomographic spectroscopic image of the tissue (135) from the microwave signals received from the selected plurality of emitter/receivers (16).
Description
wo s~t3266s ~ 1 9 1 3 1 2 ~crAlsss~06so7 MICROWAVE TOMOGRAPHIC SPECTROSCOPY
SYSTEM AND MFI HOD
Field of the Invention The invention is related to microwave fomographic imaging and in particular to imaging biological tissues to obtain internal structural imaging as well as functional imaging.
5 Background of the Invention Microwave tomographic imaging uses microwave radiation to image an object by detecting the effects the object had on the microwave beam after it has interacted with the object. With microwave radiation, it is the dielectric permittivity and conductivity properties of the tissues of 10 the object being imaged that deterrnines the nature of the interaction. The dielectric permittivity and conductivity properties of an object are expressed together as a complex permittivity.
Microwaves, as a component of the electromagnetic radiation spectrum, are in the frequency range between approximately 0.1 Giga Hertz 15 GHz to 300 GHz. This corresponds to the wavelength range between 300 mm and 1 mm. The microwave range useful for microwave imaging of biological tissues is in the range from about 0.5 to about 3 GHz, but other ranges of the microwave spectrum can be used as well. The quantum WO95/3266S 2 ~ q 1 3 1 2 PCTIUS95/06507 energy of the photons in this range of the electromagnetic spectrum comprises non-ionizing radiation.
In general, microwave imaging differs from X-rays, positron emission, ultrasound, or nuclear magnetic resonance imaging because the 5 microwave radiation interacts with the object to be imaged as a function of the complex permittivity of the object. Complex permittivity is made up of the dielectric permittivity and the dielectric loss. The dielectric permittivity is the real part and is given by the equation:
Equation 1 - ' = /o.
The relative dielectric loss is given by the imaginary part as Equation 2 - " =
2~f o Where o iS the dielectric permittivity of vacuum, ~ is the conductivity of the material and f is the working frequency. For example, water has a fairly broadband dielectric permittivity, being approximately 80 at about 1 20 GHz and falling to about 4.5 at frequencies higher than 100 GHz. Water ~iielectric loss increases from values at about 1 GHz to around 25 GHz. An additional factor affecting the permittivity of water is its temperature.
There are two basic categories of microwave imaging. The first category is static imaging based on forming images by determining the 25 absolute permittivity values of the microwave radiation after its interaction with the object. The second category is dynamic imaging which is based on variations in permittivity within the object occurring at the time of incidence of the microwave radiation. This second form of imaging is extremely useful in applications for imaging biological tissues 30 to monitor ongoing physiologic change. It must be understood, however, that both static imaging and dynamic imaging still require an active WO~5/32665 2 1 9 1 3 1 2 PCT/US95/06507 imaging process whereby a microwave scanner employs moving or scanning incident radiation and detects the changes in the microwave radiation based on interaction with the object being imaged.
Most non-biological objects that are amenable to imaging by 5 microwaves are very simple structures in terms of dielectric and conductivity variability. On the other hand, biological tissues demonstrate a wide range of relative dielectric constants. These ranges are thought to be due in large part to the interaction of the microwave radiation with charges on the surface of cellular membranes, the actual structure of the cellular membrane with its hydrophobic layer between the hydrophilic layers, and the water and electrolyte content both within and without the cellular structures. Consequently, biological tissue interaction is extremely complex and will even change with time due to the subtle change in temperature secondary to the absorption of the microwave energy used to obtain the microwave image. This absorption is converted to heat, especially by water. This is quite important because the average biological tissue contains a~roxilllately 70% water.
Tomographic microwave imaging has used a series of microwave emitters and receivers arrayed spatially around an object to be imaged. In a 1990 publication in IEEE Transactions on Biomedical Engineerin~, vol. 37 no. 3; pp. 303-12, March, 1990, titled "Medical Imaging with a Microwave Tomographic Scanner", Jofre et al., disclose a cylindrical array of microwave emitters and receivers. The array totalled 64 waveguide antennas in four groups of 16 antennas. Each waveguide antenna is capable of function as an emitter or receiver. The object to be imaged is placed within the array circle and immersed in water to minimize attenuation of the microwave incident beam as it interacts with the surface of the object. Each antenna within a group emits in sequence and the 16 antennas in the group opposite the emitting group act as receivers. This procedure is sequentially repeated for each antenna until one revolution is completed. The output microwave signal was 2.45 GHz, WO~/32665 2 1 9 1 3 1 2 PCT/US95/06507 providing a collimated field approximately 2 cm in height and having a power density of less than 0.1 milliwatt per square centimeter at the object.
The Jofre et. al structure uses a coherent phase quadrature detector to measure the magnitude and phase of the signal from the 5 receiving antennas. The data is digitized and a computer performs a reconstruction of the image based on changes in the microwave radiation.
This reconstruction is carried out by an algorithm formulated to yield an approximation of the microwave diffraction in two dimensions. The algorithm makes use of the Born approximation which assumes that 10 scattering acts as a small perturbation on the illumination and therefore the field within the body is approximated by the incident field. This approximation problem remains as a substantial limitation to microwave tomography.
In a publication in Journal of Neuroscience Methods, 36; pp.
15 239-51, 1991, entitled "Active Microwave Computed Brain Tomography:
The Response to a Challenge", Amirall et al., disclose an application of the cylindrical array in Jofre's paper to imaging the brain. The image was again reconstructed using a diffraction algorithm for cylindrical geometries using Fast Fourier Transform techniques and the Born first order 20 approximation. The data as reconstructed through the algorithm generates a contrast in permittivity values of a cut of the body as a function of the spatial coordinates of the portion of the imaged body creating that contrast in permittivity. Resolving power theoretically is limited to diffraction values of one half the wavelength of the microwave radiation.
25 For a frequency of 2.45 GHz this would mean a theoretical minimum resolution of about 6 cm in air and 7 mm in water. As a consequence of the reconstruction algorithms and limitations in the electronics used in the devices, these theoretical values are not achieved.
The validity of the first order approximations and the 30 algorithms used in the above device limit imaging to static images of small bodies such as limbs. In the case of larger bodies, such as a human '1'09a/32665 2 1 9 1 3 1 2 PCI/IJS95/06507 head, the reconstructed image would only show correctly the outer contour of the body but not the internal structure.
Using dynamic imaging, image reconstruction is based on the difference in diffracted fields recorded from several data sets taken from a 5 body with a changing dielectric contrast. Amirall et al., were able to achieve intemal imaging within the larger bodies, however, resolution was approximately only half the theoretical predictions.
Summary of the Invention The invention is a system for non-invasive microwave 10 tomographic spectroscopy of tissue using a plurality of microwave emitter-receivers spatially oriented to the tissue, an interface medium placed between the emitter-receivers, control means operably coupled between a power source and the plurality of microwave emitter-receivers for selectively controlling power to the plurality of emitter-receivers and for 15 receiving microwave signals from the plurality of emitter-receivers so that multiple frequency microwave radiation is emitted from a selected plurality of emitter-receivers and received by a selected plurality of emitter-receivers after interacting with and passing through the tissue, and computational means operably connected to the control means for 20 computing a tomographic spectroscopic image of the tissue from the microwave signals received from the selected plurality of emitter-receivers.
The invention includes a method for non-invasive microwave tomographic spectroscopy of tissue using steps of providing a 25 microwave radiation power source, providing a plurality of microwave radiation emitter-receivers, controlling the plurality of microwave radiation emitter-receivers so that a plurality of emitter-receivers are able to emit multiple microwave frequency radiation from the power source to a plurality of emitter-receivers that are receiving the microwave radiation, 30 placing an interface medium between the emitting and receiving microwave emitter-receivers, placing tissue to be irradiated within the interface medium, emitting the microwave radiation from the microwave wos~/3266s ~ I 9 1 3 ~ 2 PCI/US95~0650~
emitter-receivers, receiving the microwave radiation in the microwave emitter-receivers after interacting with the tissue, and measuring a change in the microwave radiation after interacting with the tissue.
This invention embodies a method of identifying discrete 5 signals correlating to specific antenna arrays in a microwave tomographic spectroscopy tissue imaging system using steps of providing a microwave tomographic spectroscopy system having a microwave power source, a plurality of microwave emitters-receivers, an interface medium between the microwave emitters-receivers, control means for providing 10 microwave signals to the emitters-receivers and for receiving microwave signals from the emitters-receivers after the microwave signals have interacted with the tissue, orienting a tissue to be imaged in the interface medium, encoding the signals originating simultaneously from different emitters and interacting with the tissue, and decoding the signals received 15 by different receivers so that the signals are distinguishable according to the originating emitter.
This invention also embodies a method of non-invasive microwave tomographic spectroscopy of tissue using the steps of designating a target tissue area for microwave irradiation, determining 20 expected tissue dielectric values for the designated target tissue area, providing a multiple frequency microwave radiation emitting and receiving system having microwave emission means, microwave receiving means and microwave analysis means, irradiating the target tissue area with microwave radiation from the microwave emission 25 means, receiving the microwave radiation from the irradiated target tissue area with the receiving means, analyzing the received microwave radiation with the analysis means to obtain an observed tissue dielectric values, and comparing the observed tissue dielectric values with the expected tissue dielectric values to determine a physiologic state of the 30 tissue within the designated target tissue area.
Brief Description of the Drawing~
WO 95/32665 2 1 9 1 3 1 2 PCT/USg5/06507 Figure 1 is a schematic diagram of the microwave tomographic spectroscopy system of the invention.
Figure 2 is a schematic diagram of the microwave tomographic spectroscopy system of the invention.
5Figure 3 is a flow diagram of the algorithm for the reverse problem solution.
Figure 4 is a flow diagram of an alternate reconstruction algorithm for the reverse problem solution.
Figure 5 is a graph of canine cardiac tissue dielectric 10characteristics as a function of heart cycle.
Figure 6 is a graph of canine cardiac tissue dielectric characteristics as a function of heart cycle.
Figure 7 is a graph of canine cardiac tissue dielectric characteristics as a function of occlusion and re-perfusion.
15Figure 8 is a graph of canine cardiac tissue dielectric characteristics as a function of occlusion and re-perfusion.
Figure 9 is a graph of canine cardiac tissue dielectric characteristics as a function of occlusion and re-perfusion.
Figure 10 is a graph of canine cardiac tissue dielectric 20characteristics as a function of occlusion and re-perfusion.
Figure 11 is a graph of canine cardiac tissue first order and second order dielectric characteristics as a function of time and frequency of microwave emission.
Figure 12 is a graph of canine cardiac tissue first order and 25second order dielectric characteristics as a function of time and frequency of microwave emission.
Figure 13 is a graph of first order canine cardiac tissue dielectric characteristics correlated to frequency of microwave emission.
Figure 14 is a graph of blood oxygen content correlated to 30second order canine cardiac tissue dielectric characteristics and frequency ofmicrowave emissions.
wo~s/3266s 2 ~ 9 1 3 1 2 PCTIUS9 /36507 Figure 15 is a graph of blood oxygen contents correlated to first order dielectric correlation coefficients and frequency of microwave emissions.
Figure 16 is a graph of blood oxygen contents correlated to 5 second order dielectric correlation coefficients and frequency of microwave emissions.
Figure 17 is a graph of first order and second order dielectric coefficients correlated to total hemoglobin correlation coefficients and frequency of microwave emissions.
Figure 18 is a graph of second order dielectric characteristics for a human left ventricular myocardium normal tissue to diseased tissue correlated by frequency of microwave emissions.
Figure 19 is a graph of first order ~liPlectric characteristics for a human left ventricular myocardium normal tissue to diseased tissue correlated by frequency of microwave ~mi~sions.
Figure 20 is an expanded scale graph of the second order dielectric characteristics for a human left ventricular myocardium normal tissue to diseased tissue correlated by frequency of microwave emissions shown in Figure 18.
Figure 21 is a flow diagram of an ablation choice algorithm.
Detailed Description of the Invention Figures 1 and 2 are each schematic diagrams of the tomographic spectroscopy system 10 of this invention. Utility of this invention encompasses many fields, however the pfefel~ed field described below is that of medical uses. More particularly, the embodiments of the invention claimed below relate to non-invasive diagnosis and therapy for heart arrhythmias. The microwave system enables rapid and highly accurate non-invasive detection and localization of cardiac arrhythmogenic foci, as well as non-invasive cardiac mapping capabilities.
System 10 accomplishes these procedures using a multiple frequency regimen, signal encoding techniques, improved mathematical algorithms, and previously unrecognized correlation functions. These and other -U O 95/32665 PCI-/l,TS~5/06507 features of the invention will become apparent from the more detailed description below.
Identification of the origin of cardiac arrhythmias has previously depended on one of three principal techniques: catheter - 5 mapping, electrical excitation mapping during cardiac surgery, or body surface mapping of electric potentials or magnetic fields. Each of these techniques has substantial risks and limitations. For example, catheter mapping and excitation mapping during surgery are inherently invasive, access limited, and time sensitive. Body surface mapping can be performed in a non-invasive, low risk manner but with such poor definition that the data is generally considered unsuitable for directing therapy. The mapping may be performed using either sequential temporal changes in the electrical potential distribution on the surface of the body or sequential changes in magnetic fields on the body surface.
The invention does not require insertion of a catheter into a body, nor does it require inserting probes into cardiac tissue. However, reliable and precise (2-5 mm) three dimensional reconstruction of the heart and its electrical excitation sequence is now possible using this invention. Use of the techniques listed below for ablation of arrhythmogenic sites is non-invasive and advantageously utilizes the different frequencies and directions of energy available so that the ablation threshold will occur only at the designated location. The invention does anticipate invasive procedures, for example, ablation systems delivered by catheters or surgical procedures to accomplish physician directed therapy.
As briefly mentioned above, the invention utilizes novel correlation functions. These functions relate to tissue physical properties and changes of those properties during cell excitation. In particular, the dielectrical behavior of biological tissue can be defined by two characteristic parameters: dielectric permeability and conductivity. The parameter functions include frequency, temperature, and tissue type. The tissue type parameter provides opportunities for detection of anatomical structure by measuring transmitted, i.e. rPflecte~l and scattered, electromagnetic energy WO~ai32665 2 ~ 9 1 3 1 2 Pcr~ls9s/06so7 through tissue. For homogenous objects the dielectric characteristics can be readily detected by measuring amplitude and phase of transmitted electromagnetic radiation. However, the problem is more complicated when trying to measure the dielectric values of radiation transmitted 5 through non-homogenous biological tissue simply by using measured amplitude and phase of the transmitted wave. This problem is known as the "inverse" or "reverse" problem and has attracted some attention to its solution. This invention incorporates the strong dependance of tissue characteristics on temperature, and solves the "reverse" problem in novel 10 ways by using multiple frequency and multiple position emitter-receiver configurations.
Referring to Figures 1 and 2, system 10 comprises microwave emitter-receiver sub-assembly 14 suitable for mounting a plurality of microwave emitters-receivers 16. A preferred configuration of emitters-15 receivers is in a circular array. However, any other 3-Dimensional or 2-Dimensional array configurations, suitable for certain parts of the body or for the whole body (for example, the "head," "heart," "arm," "leg," etc.), is usable in this invention. Each emitter-receiver 16 may be enabled for radial movement relative to the circular array.-- Sub-assembly 14 may also 20 comprise a plurality of vertically stacked emitters-receivers. A power source 19 provides narrow pulse-width electromagnetic energy signals to each emitter of not more than about 10 mW/cm2 incident power density on an object. Preferably, the frequency band width of these narrow pulse-width signals is centered between about 0.1 GHz to about 6 GHz, and more 25 preferably within the frequency range of about 0.2 GHz to about 2.5 GHz.
Power source 19 may comprise either a plurality of power sources or a single power source, such as a generator. In the embodiment of Figure 2, power source 19 comprises a sweeping diagnostic generator 22, a diagnostic generator control block 24, an ablation generator 27, and an ablation 30 generator control block 29. Sweeping diagnostic generator 22 provides multiple frequency low power energy for use in diagnostic applications, while ablation generator 27 provides high power energy for microwave W095132665 ~ i 9 1 3 1 2 PCr/US9S/06507 ablation of designated tissue regions. Selection of either of the above generators is accomplished by switch 33 which connects generator output with the emitters 16.
A channelization mechanism 35 is provided for activation 5 and control of channels i, i+1, i+n, for energy emission and reception.
This subsystem comprises a channel number switch 36, an amplitude attenuator-detector manipulation (ADM) 39, a phase rotator-detector 42, an amplitude detector 45, a phase detector 48, and an antenna mode switch 53.
In diagnostic operation, channel number switch 36 connects the output of the diagnostic generator 22 with the input of the emitter (or a multiple of emitters) at any particular time. In the ablation or therapeutic mode, the switch connects all channels with the output of the ablation generator 27.
Amplitude attenuator-detector 39 and phase rotator-detector 42 are in the emitter path of all channels. Arnplitude attenuator-detector 39 attenuates the amplitude of ~mitte~l power, and with phase rotator-detector 42 detects and encodes the output signal. Amplitude detector 45 and phase detector 48 are in the received path of all channels and, in the diagnostic mode, detect and decode the amplitude and phase of the received signal. It is recognized that other coding means, such as polarity, may require additional encoding/de-coding components. Antenna mode switch 53 functions in all channels to connect the output of the emitter path with the antenna or input path, at the receive. path, with the same antenna.
Computation and control module means 65 includes a central processing unit (CPU) 68, an interface subsystem 72, a display 75 and a display software 77, as well as a memory 82. The interface subsystem 72 consists of a digital-to-analog converter(s) (DAC) 86, a multiplexer 89, an analog-to-digital converter (ADC) 92, and a control block 94 which creates time synchronization of controlled processes and receives data to be analyzed.
An auxiliaries subsy~elli 102 comprises a thermostatic shield 105 for controlling the temperature of an interface me~ m 106. A suitable interface medium, for example, would be a fluid such as a solution of WO 9a/32665 PCT/US95/06507 titanium and barium. Other suitable liquids (or substrates), such as specially homogenized fatty solutions, are usable in this invention. These liquids would have a preliminary dielectrically adjustable dielectric permittivity between about 50 and 90 at 2.45 GHz and a dielectric loss 5 between about 5 and 25, between the emitters-receivers 16; the subsystem 102 also comprises a thermostatic control block 108 for controlling thermostatic shield 105, and a basic channel control block 111 for control of the received signal from the Bi control channels when the system 10 is in a calibration mode. Additional auxiliary components may be added 10 depending on desired performance features of the system, for example, an electrocardiogram analyzer and/or a printer 119 may be useful to the system 10.
In a sequential multiple frequency tomographic spectroscopy system 10, target tissue 135 is irradiated in sequence with low energy 15 microwave radiation from the first to the n~h emitter (receiver) 16, while simultaneously taking measurement of the received signals in (emitter) receivers 16 which in that particular step of the sequence are not functioning as an emitter. Several emitter-receivers 16 are used to receive signals emitted by a single emitter - receiver 16 in any given instance of 20 time. The system 10 rapidly changes channel number and antenna mode in sequence according to the above configuration. After one cycle of n-channel emissions and receptions, sweeping diagnostic generator 22 provides another cycle of n-channel switched measurements. The total quantity of cycle measurements is normally not more than N x M, where 25 N is the quantity of antennas, and M is the quantity of used diagnostic frequencies. It is also recognized that simultaneous measurements may be obtained using a multiple encoded frequency configuration. Following the measurements, system 10 solves the "reverse" problem according to the received information and the novel algorithms described more fully 30 below in relation to Figures 3 and 4. When measuring physiologic changes it is important to understand the time it takes for a physiologic 2~ 9 1 3 1 2 ~'0 95/32665 PCIIUS9~106507 event to occur, for example a myocardial contraction. These time periods are defined as tissue event time cycles.
Data acquisition in system 10 is performed in time intervals which are a fraction of a tissue event time cycle so that data acquisition 5 may occur many times during each tissue event and are stored in memory 82. Reconstruction time is fast enough that body motion is not a problem.
Anatomical object structure and temperature profiles are observable on display 75, may be manipulated using routines of display software 77, and may be printed using printer 119. The arrhythmogenic zones of the heart 10 are defined as those regions with particular ' and " values. Spatial coordinates of these zones are defined with the help of the display software, the CPU, and the memory.
During measurement cycles, system 10 periodically makes temperature control corrections of the interface medium 106 with the aide 15 of the thermostatic control block 108. System 10 also synchronizes with the heart cycle in which the tissue is resident using electrocardiogram analyzer 115.
A key feature of system 10 which facilitates the speed and accuracy of calculation is the use of a coding device for encoding the 20 microwave signals supplied to the emitters. When the receivers receive the cor~e~onding signals after interaction with the tissue, the signals are distinguishable by their originating emitter or emitter group. Preferred encoding techniques are phase, amplitude, or polarity modulation;
however it is also within the scope of the invention to employ frequency 25 modulation. Frequency modulation may be useful in certain applications where simultaneous emissions from a plurality of emitters are required.
System 10 is one embodiment for using the novel method steps of this invention which permits non-invasive microwave tomographic spectroscopy of tissue. The method comprises the steps of:
30 providing a microwave radiation power source; providing a plurality of microwave radiation emitter-receivers; and controlling the plurality of microwave radiation emitter-receivers so that a plurality of emitter-2~913~2 WO 9~/32665 PCT./llS95~06507 receivers are able to emit multiple microwave frequency radiation from the power source to a plurality of emitter-receivers that are receiving the microwave radiation. Further steps include: placing an interface medium between the emitting and receiving microwave emitter-receivers for 5 dielectric matching; placing tissue to be irradiated within the interface medium; emitting the microwave radiation from the microwave emitter-receivers; receiving the microwave radiation in the microwave emitter-receivers after interacting with the tissue; and measuring a change in the microwave radiation after interacting with the tissue.
As disclosed above, novel algorithms are used to solve the "reverse" problem calculations. In this invention, there are no approximations, such as the Born approximation discussed above, used to define dielectric or conductivity parameters of non-homogenous irradiated tissue objects. Rather, the measuring step of the above method 15 incorporates both old and new concepts to refine and render useful the data derived from this form of electromagnetic imaging. In particular, and as shown in the flow diagram of Figure 3, the measuring steps comprise computations using an input data formation component 220, a direct problem solution component 222, a reverse problem solution component 20 224, a multiple frequency correlation component 226, a computer visualization control 236, and a tomographic spe~l~osco~ic image 238.
The direct problem solution is a known calculation which solves microwave propagation from emitter to receiver through a biological means. Solution of the reverse problem a'lows precise 25 computation and generation of a tomographic spectroscopically useful image of the tissue based on the measured change of the microwave radiation. The reverse problem solution steps comprise: determination of a functional formation component 228 which sums the input from all emitters-receivers; using a gradient formation component 230 as a 30 derivative of the functional formation component to simplify processing speed; calculating a minimization parameter tau to verify the accuracy of the gradient function and to reconstruct in the most accurate manner; and 2 ~ 9 1 3 1 2 '0 95/32665 PCI'/US95~06507 performing an E" calculation 234. The E~ calculation 234 uses the follo wing:
Equation 3 E~ = ' + i"
Where ' said ~" are the values of dielectric permittivity and loss measured by the invention and i represents the imaginary number. Using ~ as a representative value of ' and " is a convenient mathematical tool.
It should be understood that the invention may also use either ' and/or 10 " as the measured dielectric parameter for generating an image. The reason for using ~ that dielectric contrast between tissue and/or tissue physiologic states may be found in either a difference or change in ' and/or ". If ' and " are calculated together as f then any dielectric change in either ' or " will be detected in an ~ calculation. As will be 15 seen later, some physiological dielectric changes are best evaluated by using only ' or ". It is important to recognize that wherever ~ is used, ' or " can also be used in place of ~.
The flow chart depicted in Figure 4 represents an embodiment of the present invention which can be used in a catheter 20 system as well. Data is fed into a direct problem solution step 240 from a working arrays formation step 242 and an antenna simulation step 244.
The working arrays formation step 242 receives data from a frequency anci temperature correlation step 248 which derived its initial values from a zero approximation step 250. The antenna simulation step 244 provides 25 values for starting the calculation process acting as a base line from which to construct an image. l:)irect problem solution step 240 then is able to solve an image problem based on knowing what the amplitude and phase of the emitted microwave energy is and making an assumption as to what the biological tissue dielectric effects will be and calculating an expected 30 amplitude and phase value for the transmitted microwave energy. This wos~/3266s ~ 1 9 1 3 1 2 PcT~Ts95l0650~
solution from the direct problem solution step 240 is then passed to reverse problem solution step 252 comprising an e~uation system formation step 254, a Jacobian formation step 256, and a matrix irreversing step 258. The reverse problem solution step 252 then calculates an image 5 of the biological tissue based on known emitted microwave amplitude and phase values and known received amplitude and phase values from the emitter receiver arrays. In effect, the reverse problem solution is generating the tomographic image by knowing the amplitude and phase of the emitted microwave energy and the amplitude and phase of the 10 transmitted or received microwave energy in order to calculate the dielectric characteristics of the biological tissue through which the microwave energy has passed. This image data from the matrix irreversing step 258 is then passed through an error correcting iteration process involving an error estimfition step 260 and a first error correction 15 step 262. For each value of amplitude and phase emitted and received, where i is equal to 1-n, the matrix irreversing step 258 in conjunction with error estimation 260 and first error correction 262 forms an iterative loop that begins with inputing the first grid point }~T into the error estimation step 260. For each value of i, from 1-n, a }j + 1, Tj + I is 20 generated in which j is the grid number in the coordinate system for generating the two or three dimensional image construct and where j is equal to values from 1-n. After each ~, T value has undergone an error estimation and first error correction, the value is then passed to an anatomical and T reconstruction and anatomy error estimation step 264.
25 At this point the value as fed into error estimation step 264 is compared with the E" value and if the error estimation has occurred the value is passed onto an anatomical structure and T visualization step 266 which serves the purpose of generating the two dimensional or three dimensional image of the biological tissue based on dielectric contrast. If, 30 however, the error estimation step results in a no response, a data point is passed to a second error correction step 268 which then adjusts, in WO9al~2665 ~ 3 1 2 PCT/US95/06507 conjunction with the first correction step 262, the values generated by frequency and temperature correlation step 248.
Figure 5 is a graph demonstrating the capability of system 10 to detect cardiac excitation by changes in dielectric characteristics of cardiactissue. In particular, Figure 5 shows the change in ' values at the onset and throughout the period ~Tl of an electrical excitation process and during the transition period /`T2 to recovery. Figure 6 discloses similar detection capabilities for system 10, but for values of the " dielectric parameter. In both Figures 5 and 6, each point represents a mean value for seven measurements.
Figures 7-10 are graphs demonstrating the percent change of a selected dielectric characteristic, for multiple frequencies, during a series ofcoronary arterial occlusions. Figures 7 and 8 disclose, over a long duration, a series of sho!t occlusions followed by a long occlusion. These figures demonstrate the correlation of dielectric characteristics for ' and "
depending on the degree of cardiac ischemia. This pattern of dielectric changes conforms with the known tissue phenomenon of a protective effect from pre-conditioning prior to a total occlusion. Figures 9 and 10 disclose, over a short duration, a series of short occlusions followed by a long occlusion. These figures support the conclusions stated above in relation to Figures 7 and 8.
Figure 10 provides further example of the value of multiple frequency or spectroscopic analysis of tissue. In this figure, the curve of the values of percent change of " at 4.1 GHz is relatively flat and less useful as compared to the corresponding values at either 0.2 GHz or 1.17 GHz. This highlights the need for system 10 to detect tissue excitation phenomena and other physiological events, e.g. ischemia, using multiple frequency techniques which might otherwise remain undetected or not useful in a single frequency analysis. This is further demonstrated in the E~(f) graphs of Figures 11 and 12, in which curves 145, 147, 149, 151, 153, and 155 represent time after occlusion (i.e., acute ischemia) of 0, 15, 30, 45, 120, and Wo 9a/3266a 2 ~ 9 1 3 1 2 PCr/l~S9~/06507 125 minutes respectively for ' (shown by ~ curves) and " (shown by o curves). The value of ~ is ~~ before. Reperfusion occurs at time 125 minutes, and is represented by curves 155. These figures demonstrate that if analysis is limited to a single frequency, then very little useful data is 5 derived during short tissue excitation periods. However, if multiple frequency analysis is conducted essentially simultaneously then the tissue physiological phenomena are clearly exhibited.
Figures 13 and 14 disclose the correlation of dielectric characteristics to blood oxyhemoglobin content. In Figure 13, the dielectric 10 characteristic is the percent of ('(HbO2)-'(86.9))/'(86.9), and in Figure 14 the dielectric characteristic is the percent of ("(HbO2)-~"(86.9))/"(86.9). Ineach figure the frequency curves 161, 163, 165, 167, 169, 171, and 173 correspond to 0.2 GHz, 1.14 GHz 2.13 GHz, 3.12 GHz, 4.01 GHz, 5.0 GHz, and 6.0 GHz, respectively.
The dielectric permittivity of oxyhemoglobin (HbO2), the partial pressure of oxygen (PO2) and total hemoglobin (tHb) content are correlated to microwave frequency range 0.2 - 6 MHz in Figure 15. The highest degree of correlation for oxyhemoglobin occurs between the frequency range 0.5 - 2.5 MHz. Through this range the dielectric 20 permittivity value ' iS most sensitive to the oxyhemoglobin saturation content of blood.
The correlation coefficient curve for ~", dielectric loss, is aisclosed in Figure 16. The correlation coefficient for HbO2 is highest at approximately 2 GHz with the correlation coefficient for PO2 approaching 25 unity between 2.5 and 4 GHz.
The correlation coefficient studies disclosed in Figures 15 and 16 are representative of the invention's ability to distinguish between oxyhemoglobin (HbO2) saturation percentage and PO2. Both of these values are important pieces of information useful to health care providers.
30 Presently, there exists real time bed side photometric means for determining oxyhemoglobin saturation percentage called an oximeter.
W09~13266~ 2 1 9 1 3 1 2 PCTIUS95/06507 However, in order to obtain a PO2 value, arterial blood must be withdrawn from a patient into specialized syringes and put through a machine capable of directly measuring the partial pressure of gases in a liquid.
The ' and " curves for total hemoglobin as a reference 5 correlation are depicted in Figure 17. The ' curve as shown is a fairly flat correlation curve that is fairly non-correlative, maintaining values of correlation less than -0.995 throughout most of the curve. The " curve, however, shows an increase in correlation to total hemoglobin for the microwave frequency range between 4 and 5 GHz. As noted above in the 10 discussions pertaining to Figures 3 and 4, correlation values for oxyhemoglobin PO2 and total hemoglobin may accurately derive from these correlation curves during a single frequency range scan from 0.2-6 GHz and calculating the dielectric permittivity ' and dielectric loss "
values for blood. The concentration of oxyhemoglobin saturation would 15 then be best correlated with the ' value at, or about, 1.5 GHz, the PO2 value would then be calculated from the correlation value of the dielectric loss, ", calculated at, or about, 3.5 GHz, and tHb could be calculated from the correlation value of the dielectric loss curve, ", calculated at, or about,4.5 GHz. Each scan through the frequency range from 0.2 - 6 GHz would 20 require no more than several milliseconds of microwave exposure and then computing the value calculations. Thus, the present invention could feasibly be used at the bedside for virtual real time assessment of these parameters.
The present invention is able to provide a real time bedside 25 monitoring of HbO2 saturation percentage and PO2 values. The present invention does so without necessitating removal of blood from the patient and the delay and cost of sending the blood to the laboratory for analysis.
This invention is not limited to HbO2 and PO2 values. Any blood and tissue component possessing a dielectric contrast characteristic is 30 capable of direct rneasurement and real time evaluation, non-invasively, using this invention. The present invention also possesses an ability to WOg~/32665 2 1 ~ 1 3 1 2 PCrlUS95/06507 detect dielectric characteristic changes that occur in a tissue that is becoming diseased. By way of example, a weakened diseased aneurysmal portion of a ten year old male's left ventricle was repaired. During this repair the diseased portion was resected from the heart such that the diseased portion was removed entirely. This requires that the resection margins contain normal myocardium. The invention was used to evaluate this piece of resected heart tissue and the test results are presented in Figures 18-20.
The E" dielectric loss characteristic of normal myocardium is 10 shown in Figure 18 as a curve 200 measured over a microwave frequency range between 0.2 and 6 GHz. Throughout the entire frequency range this normal tissue is distinguishable from the abnormal tissue as shown by curve 202.
Figure 19 shows the ' dielectric permittivity characteristic 15 curves for this same tissue sample. Normal tissue has a ' single curve represented by curve 204. The abnormal tissue is shown in curve 206. The normal myocardial tissue is distinguishable from abnormal myocardial tissue over the entire microwave frequency range used in the present invention.
Figure 20 is an expanded scale graphic representation of the same " dielectric loss data of Figure 18. Curve 208 represents the " for normal myocardial tissue with curve 210 representing the " values for abnormal cardiac tissue.
The present invention is able to use this dielectric characteristic difference to generate an image. For example, as system 10 of Figures 1-4 scans a patient's chest, an anatomical image of the organs is obtained based on the dielectric characteristic differences between the various tissues as demonstrated in Figures 5-12 and 18-20. Additionally, the invention facilitate anatomical location of diseased abnormal tissue within normal tissue. This anatomical information is useful in many ways. An example of one important use would be to direct real time WO~a/3266a 2 1 9 1 3 1 2 PCT~Sg5/06'07 therapy. Often abnormal myocardial tissue causes deleterious rhythm disturbances. Unfortunately, this abnormal tissue may be visually indistinguishable from surrounding normal myocardium. The present invention provides real time imaging of the abnormal tissue based on the dielectric characteristic differences such as those detected in Figures 18-20.
Using fast reconstruction routines and scanning through the frequency range in at time rates that are fractions of the tissue event time cycle, a clinician creates a map of the abnormal tissue. Depending upon which frequency and dielectric characteristic is evaluated, the investigator may reconstruct the dielectric properties to generate a functional excitation map through the abnormal tissue area or alternatively may reconstruct a temporal change map and correlate those temporal changes to known electrical markers for anomalies within the tissue. The clinician may then direct ablation therapy to remove this abnormal rhythm focus and evaluate the adequacy of the tissue removal.
An embodiment of the present invention using laser or microwave sources of ablation is disclosed in Figure 21. As disclosed, a method for ablation of a lesion, for example, an arrhythmogenic focus within normal myocardial tissue, is performed beginning with inputing information into an input data formation step 300 from anatomical structure analysis derived from data generated by the invention disclosed in Figure 2 and expected temperature distribution values. The input data formation step uses information from a microwave power source as an approximation step 302 or a laser power source as an approximation step 304 to derive input to be fed to a direct problem solution for microwave 306 or direct problem solution for laser control 308. A determination step for determining the possible available microwave and laser power sources is undertaken at step 310. The result of this determination is passed onto a sources and lesions correlation databank 312 to derive an approximation step 314, also taking input from an antenna simulation step 316. The current expected temperature is calculated at step 318 and corrected for a temperature non-linearity at step 320. The results of the direct problem -wo ss/3266s 2 ~ 9 1 3 1 2 PCTIUS95/06507 solutions for microwave or laser 306, 308 in conjunction with the corrected current temperature from 320 is incorporated into a biological heat equation solution 322 to derive an actual temperature solution.
Temperature distribution from the bioequation step 322 is passed to a lesion localization step 324 which provides data back to the source lesion correlation databank 312 for running the next approximation through to the input data formation 300 for the next determination of the bioheat equation solution step 322. Information from the equation solution step 322 is also passed to a different necessary lesion current lesion formation step for comparing the current lesion size with the estimated necessary lesion size to determine if optimum therapy has been achieved or not. If treatment has been achieved, the decision then passes to optimal region step 328. If the current lesion is different than the necessary lesion, the different information is passed back to step sources lesion correlation databank 312 for a reapproximation at step 314 on through input data formation 300 to undertake the next treatment in order to more closely approximate the necessary lesion through treatment. The number of steps through the iterative process are monitored by switch 330 with comparison of an expected location size of lesion step 332 at step 0, step 334.
For steps greater than 0, switch 330 switches to step greater than zero step 336. The entire process is continuously re-evaluated for completeness of ablation therapy and re-evaluating on a real time basis the lesion generated by analysis of the anatomical structure derived from the microwave tomographic imaging system.
The invention provides for using microwave energy in a novel approach providing rapid real time assessment of biological function and anatomical structure by reverse problem solution for the dielectric characteristics of biological tissues. The invention achieves substantial increase in processing speed as well as substantial improvement in resolving power over any known prior art. The present invention also provides for techniques in evaluating real time parameters for determining biological component concentrations or physiologic ~ - .
u 0 95132665 2 ~ 9 1 3 1 2 PCT/US95106507 characteristics based on the dielectric contrast between different states of physiologic activity for the biological compound or physiologic reaction.
SYSTEM AND MFI HOD
Field of the Invention The invention is related to microwave fomographic imaging and in particular to imaging biological tissues to obtain internal structural imaging as well as functional imaging.
5 Background of the Invention Microwave tomographic imaging uses microwave radiation to image an object by detecting the effects the object had on the microwave beam after it has interacted with the object. With microwave radiation, it is the dielectric permittivity and conductivity properties of the tissues of 10 the object being imaged that deterrnines the nature of the interaction. The dielectric permittivity and conductivity properties of an object are expressed together as a complex permittivity.
Microwaves, as a component of the electromagnetic radiation spectrum, are in the frequency range between approximately 0.1 Giga Hertz 15 GHz to 300 GHz. This corresponds to the wavelength range between 300 mm and 1 mm. The microwave range useful for microwave imaging of biological tissues is in the range from about 0.5 to about 3 GHz, but other ranges of the microwave spectrum can be used as well. The quantum WO95/3266S 2 ~ q 1 3 1 2 PCTIUS95/06507 energy of the photons in this range of the electromagnetic spectrum comprises non-ionizing radiation.
In general, microwave imaging differs from X-rays, positron emission, ultrasound, or nuclear magnetic resonance imaging because the 5 microwave radiation interacts with the object to be imaged as a function of the complex permittivity of the object. Complex permittivity is made up of the dielectric permittivity and the dielectric loss. The dielectric permittivity is the real part and is given by the equation:
Equation 1 - ' = /o.
The relative dielectric loss is given by the imaginary part as Equation 2 - " =
2~f o Where o iS the dielectric permittivity of vacuum, ~ is the conductivity of the material and f is the working frequency. For example, water has a fairly broadband dielectric permittivity, being approximately 80 at about 1 20 GHz and falling to about 4.5 at frequencies higher than 100 GHz. Water ~iielectric loss increases from values at about 1 GHz to around 25 GHz. An additional factor affecting the permittivity of water is its temperature.
There are two basic categories of microwave imaging. The first category is static imaging based on forming images by determining the 25 absolute permittivity values of the microwave radiation after its interaction with the object. The second category is dynamic imaging which is based on variations in permittivity within the object occurring at the time of incidence of the microwave radiation. This second form of imaging is extremely useful in applications for imaging biological tissues 30 to monitor ongoing physiologic change. It must be understood, however, that both static imaging and dynamic imaging still require an active WO~5/32665 2 1 9 1 3 1 2 PCT/US95/06507 imaging process whereby a microwave scanner employs moving or scanning incident radiation and detects the changes in the microwave radiation based on interaction with the object being imaged.
Most non-biological objects that are amenable to imaging by 5 microwaves are very simple structures in terms of dielectric and conductivity variability. On the other hand, biological tissues demonstrate a wide range of relative dielectric constants. These ranges are thought to be due in large part to the interaction of the microwave radiation with charges on the surface of cellular membranes, the actual structure of the cellular membrane with its hydrophobic layer between the hydrophilic layers, and the water and electrolyte content both within and without the cellular structures. Consequently, biological tissue interaction is extremely complex and will even change with time due to the subtle change in temperature secondary to the absorption of the microwave energy used to obtain the microwave image. This absorption is converted to heat, especially by water. This is quite important because the average biological tissue contains a~roxilllately 70% water.
Tomographic microwave imaging has used a series of microwave emitters and receivers arrayed spatially around an object to be imaged. In a 1990 publication in IEEE Transactions on Biomedical Engineerin~, vol. 37 no. 3; pp. 303-12, March, 1990, titled "Medical Imaging with a Microwave Tomographic Scanner", Jofre et al., disclose a cylindrical array of microwave emitters and receivers. The array totalled 64 waveguide antennas in four groups of 16 antennas. Each waveguide antenna is capable of function as an emitter or receiver. The object to be imaged is placed within the array circle and immersed in water to minimize attenuation of the microwave incident beam as it interacts with the surface of the object. Each antenna within a group emits in sequence and the 16 antennas in the group opposite the emitting group act as receivers. This procedure is sequentially repeated for each antenna until one revolution is completed. The output microwave signal was 2.45 GHz, WO~/32665 2 1 9 1 3 1 2 PCT/US95/06507 providing a collimated field approximately 2 cm in height and having a power density of less than 0.1 milliwatt per square centimeter at the object.
The Jofre et. al structure uses a coherent phase quadrature detector to measure the magnitude and phase of the signal from the 5 receiving antennas. The data is digitized and a computer performs a reconstruction of the image based on changes in the microwave radiation.
This reconstruction is carried out by an algorithm formulated to yield an approximation of the microwave diffraction in two dimensions. The algorithm makes use of the Born approximation which assumes that 10 scattering acts as a small perturbation on the illumination and therefore the field within the body is approximated by the incident field. This approximation problem remains as a substantial limitation to microwave tomography.
In a publication in Journal of Neuroscience Methods, 36; pp.
15 239-51, 1991, entitled "Active Microwave Computed Brain Tomography:
The Response to a Challenge", Amirall et al., disclose an application of the cylindrical array in Jofre's paper to imaging the brain. The image was again reconstructed using a diffraction algorithm for cylindrical geometries using Fast Fourier Transform techniques and the Born first order 20 approximation. The data as reconstructed through the algorithm generates a contrast in permittivity values of a cut of the body as a function of the spatial coordinates of the portion of the imaged body creating that contrast in permittivity. Resolving power theoretically is limited to diffraction values of one half the wavelength of the microwave radiation.
25 For a frequency of 2.45 GHz this would mean a theoretical minimum resolution of about 6 cm in air and 7 mm in water. As a consequence of the reconstruction algorithms and limitations in the electronics used in the devices, these theoretical values are not achieved.
The validity of the first order approximations and the 30 algorithms used in the above device limit imaging to static images of small bodies such as limbs. In the case of larger bodies, such as a human '1'09a/32665 2 1 9 1 3 1 2 PCI/IJS95/06507 head, the reconstructed image would only show correctly the outer contour of the body but not the internal structure.
Using dynamic imaging, image reconstruction is based on the difference in diffracted fields recorded from several data sets taken from a 5 body with a changing dielectric contrast. Amirall et al., were able to achieve intemal imaging within the larger bodies, however, resolution was approximately only half the theoretical predictions.
Summary of the Invention The invention is a system for non-invasive microwave 10 tomographic spectroscopy of tissue using a plurality of microwave emitter-receivers spatially oriented to the tissue, an interface medium placed between the emitter-receivers, control means operably coupled between a power source and the plurality of microwave emitter-receivers for selectively controlling power to the plurality of emitter-receivers and for 15 receiving microwave signals from the plurality of emitter-receivers so that multiple frequency microwave radiation is emitted from a selected plurality of emitter-receivers and received by a selected plurality of emitter-receivers after interacting with and passing through the tissue, and computational means operably connected to the control means for 20 computing a tomographic spectroscopic image of the tissue from the microwave signals received from the selected plurality of emitter-receivers.
The invention includes a method for non-invasive microwave tomographic spectroscopy of tissue using steps of providing a 25 microwave radiation power source, providing a plurality of microwave radiation emitter-receivers, controlling the plurality of microwave radiation emitter-receivers so that a plurality of emitter-receivers are able to emit multiple microwave frequency radiation from the power source to a plurality of emitter-receivers that are receiving the microwave radiation, 30 placing an interface medium between the emitting and receiving microwave emitter-receivers, placing tissue to be irradiated within the interface medium, emitting the microwave radiation from the microwave wos~/3266s ~ I 9 1 3 ~ 2 PCI/US95~0650~
emitter-receivers, receiving the microwave radiation in the microwave emitter-receivers after interacting with the tissue, and measuring a change in the microwave radiation after interacting with the tissue.
This invention embodies a method of identifying discrete 5 signals correlating to specific antenna arrays in a microwave tomographic spectroscopy tissue imaging system using steps of providing a microwave tomographic spectroscopy system having a microwave power source, a plurality of microwave emitters-receivers, an interface medium between the microwave emitters-receivers, control means for providing 10 microwave signals to the emitters-receivers and for receiving microwave signals from the emitters-receivers after the microwave signals have interacted with the tissue, orienting a tissue to be imaged in the interface medium, encoding the signals originating simultaneously from different emitters and interacting with the tissue, and decoding the signals received 15 by different receivers so that the signals are distinguishable according to the originating emitter.
This invention also embodies a method of non-invasive microwave tomographic spectroscopy of tissue using the steps of designating a target tissue area for microwave irradiation, determining 20 expected tissue dielectric values for the designated target tissue area, providing a multiple frequency microwave radiation emitting and receiving system having microwave emission means, microwave receiving means and microwave analysis means, irradiating the target tissue area with microwave radiation from the microwave emission 25 means, receiving the microwave radiation from the irradiated target tissue area with the receiving means, analyzing the received microwave radiation with the analysis means to obtain an observed tissue dielectric values, and comparing the observed tissue dielectric values with the expected tissue dielectric values to determine a physiologic state of the 30 tissue within the designated target tissue area.
Brief Description of the Drawing~
WO 95/32665 2 1 9 1 3 1 2 PCT/USg5/06507 Figure 1 is a schematic diagram of the microwave tomographic spectroscopy system of the invention.
Figure 2 is a schematic diagram of the microwave tomographic spectroscopy system of the invention.
5Figure 3 is a flow diagram of the algorithm for the reverse problem solution.
Figure 4 is a flow diagram of an alternate reconstruction algorithm for the reverse problem solution.
Figure 5 is a graph of canine cardiac tissue dielectric 10characteristics as a function of heart cycle.
Figure 6 is a graph of canine cardiac tissue dielectric characteristics as a function of heart cycle.
Figure 7 is a graph of canine cardiac tissue dielectric characteristics as a function of occlusion and re-perfusion.
15Figure 8 is a graph of canine cardiac tissue dielectric characteristics as a function of occlusion and re-perfusion.
Figure 9 is a graph of canine cardiac tissue dielectric characteristics as a function of occlusion and re-perfusion.
Figure 10 is a graph of canine cardiac tissue dielectric 20characteristics as a function of occlusion and re-perfusion.
Figure 11 is a graph of canine cardiac tissue first order and second order dielectric characteristics as a function of time and frequency of microwave emission.
Figure 12 is a graph of canine cardiac tissue first order and 25second order dielectric characteristics as a function of time and frequency of microwave emission.
Figure 13 is a graph of first order canine cardiac tissue dielectric characteristics correlated to frequency of microwave emission.
Figure 14 is a graph of blood oxygen content correlated to 30second order canine cardiac tissue dielectric characteristics and frequency ofmicrowave emissions.
wo~s/3266s 2 ~ 9 1 3 1 2 PCTIUS9 /36507 Figure 15 is a graph of blood oxygen contents correlated to first order dielectric correlation coefficients and frequency of microwave emissions.
Figure 16 is a graph of blood oxygen contents correlated to 5 second order dielectric correlation coefficients and frequency of microwave emissions.
Figure 17 is a graph of first order and second order dielectric coefficients correlated to total hemoglobin correlation coefficients and frequency of microwave emissions.
Figure 18 is a graph of second order dielectric characteristics for a human left ventricular myocardium normal tissue to diseased tissue correlated by frequency of microwave emissions.
Figure 19 is a graph of first order ~liPlectric characteristics for a human left ventricular myocardium normal tissue to diseased tissue correlated by frequency of microwave ~mi~sions.
Figure 20 is an expanded scale graph of the second order dielectric characteristics for a human left ventricular myocardium normal tissue to diseased tissue correlated by frequency of microwave emissions shown in Figure 18.
Figure 21 is a flow diagram of an ablation choice algorithm.
Detailed Description of the Invention Figures 1 and 2 are each schematic diagrams of the tomographic spectroscopy system 10 of this invention. Utility of this invention encompasses many fields, however the pfefel~ed field described below is that of medical uses. More particularly, the embodiments of the invention claimed below relate to non-invasive diagnosis and therapy for heart arrhythmias. The microwave system enables rapid and highly accurate non-invasive detection and localization of cardiac arrhythmogenic foci, as well as non-invasive cardiac mapping capabilities.
System 10 accomplishes these procedures using a multiple frequency regimen, signal encoding techniques, improved mathematical algorithms, and previously unrecognized correlation functions. These and other -U O 95/32665 PCI-/l,TS~5/06507 features of the invention will become apparent from the more detailed description below.
Identification of the origin of cardiac arrhythmias has previously depended on one of three principal techniques: catheter - 5 mapping, electrical excitation mapping during cardiac surgery, or body surface mapping of electric potentials or magnetic fields. Each of these techniques has substantial risks and limitations. For example, catheter mapping and excitation mapping during surgery are inherently invasive, access limited, and time sensitive. Body surface mapping can be performed in a non-invasive, low risk manner but with such poor definition that the data is generally considered unsuitable for directing therapy. The mapping may be performed using either sequential temporal changes in the electrical potential distribution on the surface of the body or sequential changes in magnetic fields on the body surface.
The invention does not require insertion of a catheter into a body, nor does it require inserting probes into cardiac tissue. However, reliable and precise (2-5 mm) three dimensional reconstruction of the heart and its electrical excitation sequence is now possible using this invention. Use of the techniques listed below for ablation of arrhythmogenic sites is non-invasive and advantageously utilizes the different frequencies and directions of energy available so that the ablation threshold will occur only at the designated location. The invention does anticipate invasive procedures, for example, ablation systems delivered by catheters or surgical procedures to accomplish physician directed therapy.
As briefly mentioned above, the invention utilizes novel correlation functions. These functions relate to tissue physical properties and changes of those properties during cell excitation. In particular, the dielectrical behavior of biological tissue can be defined by two characteristic parameters: dielectric permeability and conductivity. The parameter functions include frequency, temperature, and tissue type. The tissue type parameter provides opportunities for detection of anatomical structure by measuring transmitted, i.e. rPflecte~l and scattered, electromagnetic energy WO~ai32665 2 ~ 9 1 3 1 2 Pcr~ls9s/06so7 through tissue. For homogenous objects the dielectric characteristics can be readily detected by measuring amplitude and phase of transmitted electromagnetic radiation. However, the problem is more complicated when trying to measure the dielectric values of radiation transmitted 5 through non-homogenous biological tissue simply by using measured amplitude and phase of the transmitted wave. This problem is known as the "inverse" or "reverse" problem and has attracted some attention to its solution. This invention incorporates the strong dependance of tissue characteristics on temperature, and solves the "reverse" problem in novel 10 ways by using multiple frequency and multiple position emitter-receiver configurations.
Referring to Figures 1 and 2, system 10 comprises microwave emitter-receiver sub-assembly 14 suitable for mounting a plurality of microwave emitters-receivers 16. A preferred configuration of emitters-15 receivers is in a circular array. However, any other 3-Dimensional or 2-Dimensional array configurations, suitable for certain parts of the body or for the whole body (for example, the "head," "heart," "arm," "leg," etc.), is usable in this invention. Each emitter-receiver 16 may be enabled for radial movement relative to the circular array.-- Sub-assembly 14 may also 20 comprise a plurality of vertically stacked emitters-receivers. A power source 19 provides narrow pulse-width electromagnetic energy signals to each emitter of not more than about 10 mW/cm2 incident power density on an object. Preferably, the frequency band width of these narrow pulse-width signals is centered between about 0.1 GHz to about 6 GHz, and more 25 preferably within the frequency range of about 0.2 GHz to about 2.5 GHz.
Power source 19 may comprise either a plurality of power sources or a single power source, such as a generator. In the embodiment of Figure 2, power source 19 comprises a sweeping diagnostic generator 22, a diagnostic generator control block 24, an ablation generator 27, and an ablation 30 generator control block 29. Sweeping diagnostic generator 22 provides multiple frequency low power energy for use in diagnostic applications, while ablation generator 27 provides high power energy for microwave W095132665 ~ i 9 1 3 1 2 PCr/US9S/06507 ablation of designated tissue regions. Selection of either of the above generators is accomplished by switch 33 which connects generator output with the emitters 16.
A channelization mechanism 35 is provided for activation 5 and control of channels i, i+1, i+n, for energy emission and reception.
This subsystem comprises a channel number switch 36, an amplitude attenuator-detector manipulation (ADM) 39, a phase rotator-detector 42, an amplitude detector 45, a phase detector 48, and an antenna mode switch 53.
In diagnostic operation, channel number switch 36 connects the output of the diagnostic generator 22 with the input of the emitter (or a multiple of emitters) at any particular time. In the ablation or therapeutic mode, the switch connects all channels with the output of the ablation generator 27.
Amplitude attenuator-detector 39 and phase rotator-detector 42 are in the emitter path of all channels. Arnplitude attenuator-detector 39 attenuates the amplitude of ~mitte~l power, and with phase rotator-detector 42 detects and encodes the output signal. Amplitude detector 45 and phase detector 48 are in the received path of all channels and, in the diagnostic mode, detect and decode the amplitude and phase of the received signal. It is recognized that other coding means, such as polarity, may require additional encoding/de-coding components. Antenna mode switch 53 functions in all channels to connect the output of the emitter path with the antenna or input path, at the receive. path, with the same antenna.
Computation and control module means 65 includes a central processing unit (CPU) 68, an interface subsystem 72, a display 75 and a display software 77, as well as a memory 82. The interface subsystem 72 consists of a digital-to-analog converter(s) (DAC) 86, a multiplexer 89, an analog-to-digital converter (ADC) 92, and a control block 94 which creates time synchronization of controlled processes and receives data to be analyzed.
An auxiliaries subsy~elli 102 comprises a thermostatic shield 105 for controlling the temperature of an interface me~ m 106. A suitable interface medium, for example, would be a fluid such as a solution of WO 9a/32665 PCT/US95/06507 titanium and barium. Other suitable liquids (or substrates), such as specially homogenized fatty solutions, are usable in this invention. These liquids would have a preliminary dielectrically adjustable dielectric permittivity between about 50 and 90 at 2.45 GHz and a dielectric loss 5 between about 5 and 25, between the emitters-receivers 16; the subsystem 102 also comprises a thermostatic control block 108 for controlling thermostatic shield 105, and a basic channel control block 111 for control of the received signal from the Bi control channels when the system 10 is in a calibration mode. Additional auxiliary components may be added 10 depending on desired performance features of the system, for example, an electrocardiogram analyzer and/or a printer 119 may be useful to the system 10.
In a sequential multiple frequency tomographic spectroscopy system 10, target tissue 135 is irradiated in sequence with low energy 15 microwave radiation from the first to the n~h emitter (receiver) 16, while simultaneously taking measurement of the received signals in (emitter) receivers 16 which in that particular step of the sequence are not functioning as an emitter. Several emitter-receivers 16 are used to receive signals emitted by a single emitter - receiver 16 in any given instance of 20 time. The system 10 rapidly changes channel number and antenna mode in sequence according to the above configuration. After one cycle of n-channel emissions and receptions, sweeping diagnostic generator 22 provides another cycle of n-channel switched measurements. The total quantity of cycle measurements is normally not more than N x M, where 25 N is the quantity of antennas, and M is the quantity of used diagnostic frequencies. It is also recognized that simultaneous measurements may be obtained using a multiple encoded frequency configuration. Following the measurements, system 10 solves the "reverse" problem according to the received information and the novel algorithms described more fully 30 below in relation to Figures 3 and 4. When measuring physiologic changes it is important to understand the time it takes for a physiologic 2~ 9 1 3 1 2 ~'0 95/32665 PCIIUS9~106507 event to occur, for example a myocardial contraction. These time periods are defined as tissue event time cycles.
Data acquisition in system 10 is performed in time intervals which are a fraction of a tissue event time cycle so that data acquisition 5 may occur many times during each tissue event and are stored in memory 82. Reconstruction time is fast enough that body motion is not a problem.
Anatomical object structure and temperature profiles are observable on display 75, may be manipulated using routines of display software 77, and may be printed using printer 119. The arrhythmogenic zones of the heart 10 are defined as those regions with particular ' and " values. Spatial coordinates of these zones are defined with the help of the display software, the CPU, and the memory.
During measurement cycles, system 10 periodically makes temperature control corrections of the interface medium 106 with the aide 15 of the thermostatic control block 108. System 10 also synchronizes with the heart cycle in which the tissue is resident using electrocardiogram analyzer 115.
A key feature of system 10 which facilitates the speed and accuracy of calculation is the use of a coding device for encoding the 20 microwave signals supplied to the emitters. When the receivers receive the cor~e~onding signals after interaction with the tissue, the signals are distinguishable by their originating emitter or emitter group. Preferred encoding techniques are phase, amplitude, or polarity modulation;
however it is also within the scope of the invention to employ frequency 25 modulation. Frequency modulation may be useful in certain applications where simultaneous emissions from a plurality of emitters are required.
System 10 is one embodiment for using the novel method steps of this invention which permits non-invasive microwave tomographic spectroscopy of tissue. The method comprises the steps of:
30 providing a microwave radiation power source; providing a plurality of microwave radiation emitter-receivers; and controlling the plurality of microwave radiation emitter-receivers so that a plurality of emitter-2~913~2 WO 9~/32665 PCT./llS95~06507 receivers are able to emit multiple microwave frequency radiation from the power source to a plurality of emitter-receivers that are receiving the microwave radiation. Further steps include: placing an interface medium between the emitting and receiving microwave emitter-receivers for 5 dielectric matching; placing tissue to be irradiated within the interface medium; emitting the microwave radiation from the microwave emitter-receivers; receiving the microwave radiation in the microwave emitter-receivers after interacting with the tissue; and measuring a change in the microwave radiation after interacting with the tissue.
As disclosed above, novel algorithms are used to solve the "reverse" problem calculations. In this invention, there are no approximations, such as the Born approximation discussed above, used to define dielectric or conductivity parameters of non-homogenous irradiated tissue objects. Rather, the measuring step of the above method 15 incorporates both old and new concepts to refine and render useful the data derived from this form of electromagnetic imaging. In particular, and as shown in the flow diagram of Figure 3, the measuring steps comprise computations using an input data formation component 220, a direct problem solution component 222, a reverse problem solution component 20 224, a multiple frequency correlation component 226, a computer visualization control 236, and a tomographic spe~l~osco~ic image 238.
The direct problem solution is a known calculation which solves microwave propagation from emitter to receiver through a biological means. Solution of the reverse problem a'lows precise 25 computation and generation of a tomographic spectroscopically useful image of the tissue based on the measured change of the microwave radiation. The reverse problem solution steps comprise: determination of a functional formation component 228 which sums the input from all emitters-receivers; using a gradient formation component 230 as a 30 derivative of the functional formation component to simplify processing speed; calculating a minimization parameter tau to verify the accuracy of the gradient function and to reconstruct in the most accurate manner; and 2 ~ 9 1 3 1 2 '0 95/32665 PCI'/US95~06507 performing an E" calculation 234. The E~ calculation 234 uses the follo wing:
Equation 3 E~ = ' + i"
Where ' said ~" are the values of dielectric permittivity and loss measured by the invention and i represents the imaginary number. Using ~ as a representative value of ' and " is a convenient mathematical tool.
It should be understood that the invention may also use either ' and/or 10 " as the measured dielectric parameter for generating an image. The reason for using ~ that dielectric contrast between tissue and/or tissue physiologic states may be found in either a difference or change in ' and/or ". If ' and " are calculated together as f then any dielectric change in either ' or " will be detected in an ~ calculation. As will be 15 seen later, some physiological dielectric changes are best evaluated by using only ' or ". It is important to recognize that wherever ~ is used, ' or " can also be used in place of ~.
The flow chart depicted in Figure 4 represents an embodiment of the present invention which can be used in a catheter 20 system as well. Data is fed into a direct problem solution step 240 from a working arrays formation step 242 and an antenna simulation step 244.
The working arrays formation step 242 receives data from a frequency anci temperature correlation step 248 which derived its initial values from a zero approximation step 250. The antenna simulation step 244 provides 25 values for starting the calculation process acting as a base line from which to construct an image. l:)irect problem solution step 240 then is able to solve an image problem based on knowing what the amplitude and phase of the emitted microwave energy is and making an assumption as to what the biological tissue dielectric effects will be and calculating an expected 30 amplitude and phase value for the transmitted microwave energy. This wos~/3266s ~ 1 9 1 3 1 2 PcT~Ts95l0650~
solution from the direct problem solution step 240 is then passed to reverse problem solution step 252 comprising an e~uation system formation step 254, a Jacobian formation step 256, and a matrix irreversing step 258. The reverse problem solution step 252 then calculates an image 5 of the biological tissue based on known emitted microwave amplitude and phase values and known received amplitude and phase values from the emitter receiver arrays. In effect, the reverse problem solution is generating the tomographic image by knowing the amplitude and phase of the emitted microwave energy and the amplitude and phase of the 10 transmitted or received microwave energy in order to calculate the dielectric characteristics of the biological tissue through which the microwave energy has passed. This image data from the matrix irreversing step 258 is then passed through an error correcting iteration process involving an error estimfition step 260 and a first error correction 15 step 262. For each value of amplitude and phase emitted and received, where i is equal to 1-n, the matrix irreversing step 258 in conjunction with error estimation 260 and first error correction 262 forms an iterative loop that begins with inputing the first grid point }~T into the error estimation step 260. For each value of i, from 1-n, a }j + 1, Tj + I is 20 generated in which j is the grid number in the coordinate system for generating the two or three dimensional image construct and where j is equal to values from 1-n. After each ~, T value has undergone an error estimation and first error correction, the value is then passed to an anatomical and T reconstruction and anatomy error estimation step 264.
25 At this point the value as fed into error estimation step 264 is compared with the E" value and if the error estimation has occurred the value is passed onto an anatomical structure and T visualization step 266 which serves the purpose of generating the two dimensional or three dimensional image of the biological tissue based on dielectric contrast. If, 30 however, the error estimation step results in a no response, a data point is passed to a second error correction step 268 which then adjusts, in WO9al~2665 ~ 3 1 2 PCT/US95/06507 conjunction with the first correction step 262, the values generated by frequency and temperature correlation step 248.
Figure 5 is a graph demonstrating the capability of system 10 to detect cardiac excitation by changes in dielectric characteristics of cardiactissue. In particular, Figure 5 shows the change in ' values at the onset and throughout the period ~Tl of an electrical excitation process and during the transition period /`T2 to recovery. Figure 6 discloses similar detection capabilities for system 10, but for values of the " dielectric parameter. In both Figures 5 and 6, each point represents a mean value for seven measurements.
Figures 7-10 are graphs demonstrating the percent change of a selected dielectric characteristic, for multiple frequencies, during a series ofcoronary arterial occlusions. Figures 7 and 8 disclose, over a long duration, a series of sho!t occlusions followed by a long occlusion. These figures demonstrate the correlation of dielectric characteristics for ' and "
depending on the degree of cardiac ischemia. This pattern of dielectric changes conforms with the known tissue phenomenon of a protective effect from pre-conditioning prior to a total occlusion. Figures 9 and 10 disclose, over a short duration, a series of short occlusions followed by a long occlusion. These figures support the conclusions stated above in relation to Figures 7 and 8.
Figure 10 provides further example of the value of multiple frequency or spectroscopic analysis of tissue. In this figure, the curve of the values of percent change of " at 4.1 GHz is relatively flat and less useful as compared to the corresponding values at either 0.2 GHz or 1.17 GHz. This highlights the need for system 10 to detect tissue excitation phenomena and other physiological events, e.g. ischemia, using multiple frequency techniques which might otherwise remain undetected or not useful in a single frequency analysis. This is further demonstrated in the E~(f) graphs of Figures 11 and 12, in which curves 145, 147, 149, 151, 153, and 155 represent time after occlusion (i.e., acute ischemia) of 0, 15, 30, 45, 120, and Wo 9a/3266a 2 ~ 9 1 3 1 2 PCr/l~S9~/06507 125 minutes respectively for ' (shown by ~ curves) and " (shown by o curves). The value of ~ is ~~ before. Reperfusion occurs at time 125 minutes, and is represented by curves 155. These figures demonstrate that if analysis is limited to a single frequency, then very little useful data is 5 derived during short tissue excitation periods. However, if multiple frequency analysis is conducted essentially simultaneously then the tissue physiological phenomena are clearly exhibited.
Figures 13 and 14 disclose the correlation of dielectric characteristics to blood oxyhemoglobin content. In Figure 13, the dielectric 10 characteristic is the percent of ('(HbO2)-'(86.9))/'(86.9), and in Figure 14 the dielectric characteristic is the percent of ("(HbO2)-~"(86.9))/"(86.9). Ineach figure the frequency curves 161, 163, 165, 167, 169, 171, and 173 correspond to 0.2 GHz, 1.14 GHz 2.13 GHz, 3.12 GHz, 4.01 GHz, 5.0 GHz, and 6.0 GHz, respectively.
The dielectric permittivity of oxyhemoglobin (HbO2), the partial pressure of oxygen (PO2) and total hemoglobin (tHb) content are correlated to microwave frequency range 0.2 - 6 MHz in Figure 15. The highest degree of correlation for oxyhemoglobin occurs between the frequency range 0.5 - 2.5 MHz. Through this range the dielectric 20 permittivity value ' iS most sensitive to the oxyhemoglobin saturation content of blood.
The correlation coefficient curve for ~", dielectric loss, is aisclosed in Figure 16. The correlation coefficient for HbO2 is highest at approximately 2 GHz with the correlation coefficient for PO2 approaching 25 unity between 2.5 and 4 GHz.
The correlation coefficient studies disclosed in Figures 15 and 16 are representative of the invention's ability to distinguish between oxyhemoglobin (HbO2) saturation percentage and PO2. Both of these values are important pieces of information useful to health care providers.
30 Presently, there exists real time bed side photometric means for determining oxyhemoglobin saturation percentage called an oximeter.
W09~13266~ 2 1 9 1 3 1 2 PCTIUS95/06507 However, in order to obtain a PO2 value, arterial blood must be withdrawn from a patient into specialized syringes and put through a machine capable of directly measuring the partial pressure of gases in a liquid.
The ' and " curves for total hemoglobin as a reference 5 correlation are depicted in Figure 17. The ' curve as shown is a fairly flat correlation curve that is fairly non-correlative, maintaining values of correlation less than -0.995 throughout most of the curve. The " curve, however, shows an increase in correlation to total hemoglobin for the microwave frequency range between 4 and 5 GHz. As noted above in the 10 discussions pertaining to Figures 3 and 4, correlation values for oxyhemoglobin PO2 and total hemoglobin may accurately derive from these correlation curves during a single frequency range scan from 0.2-6 GHz and calculating the dielectric permittivity ' and dielectric loss "
values for blood. The concentration of oxyhemoglobin saturation would 15 then be best correlated with the ' value at, or about, 1.5 GHz, the PO2 value would then be calculated from the correlation value of the dielectric loss, ", calculated at, or about, 3.5 GHz, and tHb could be calculated from the correlation value of the dielectric loss curve, ", calculated at, or about,4.5 GHz. Each scan through the frequency range from 0.2 - 6 GHz would 20 require no more than several milliseconds of microwave exposure and then computing the value calculations. Thus, the present invention could feasibly be used at the bedside for virtual real time assessment of these parameters.
The present invention is able to provide a real time bedside 25 monitoring of HbO2 saturation percentage and PO2 values. The present invention does so without necessitating removal of blood from the patient and the delay and cost of sending the blood to the laboratory for analysis.
This invention is not limited to HbO2 and PO2 values. Any blood and tissue component possessing a dielectric contrast characteristic is 30 capable of direct rneasurement and real time evaluation, non-invasively, using this invention. The present invention also possesses an ability to WOg~/32665 2 1 ~ 1 3 1 2 PCrlUS95/06507 detect dielectric characteristic changes that occur in a tissue that is becoming diseased. By way of example, a weakened diseased aneurysmal portion of a ten year old male's left ventricle was repaired. During this repair the diseased portion was resected from the heart such that the diseased portion was removed entirely. This requires that the resection margins contain normal myocardium. The invention was used to evaluate this piece of resected heart tissue and the test results are presented in Figures 18-20.
The E" dielectric loss characteristic of normal myocardium is 10 shown in Figure 18 as a curve 200 measured over a microwave frequency range between 0.2 and 6 GHz. Throughout the entire frequency range this normal tissue is distinguishable from the abnormal tissue as shown by curve 202.
Figure 19 shows the ' dielectric permittivity characteristic 15 curves for this same tissue sample. Normal tissue has a ' single curve represented by curve 204. The abnormal tissue is shown in curve 206. The normal myocardial tissue is distinguishable from abnormal myocardial tissue over the entire microwave frequency range used in the present invention.
Figure 20 is an expanded scale graphic representation of the same " dielectric loss data of Figure 18. Curve 208 represents the " for normal myocardial tissue with curve 210 representing the " values for abnormal cardiac tissue.
The present invention is able to use this dielectric characteristic difference to generate an image. For example, as system 10 of Figures 1-4 scans a patient's chest, an anatomical image of the organs is obtained based on the dielectric characteristic differences between the various tissues as demonstrated in Figures 5-12 and 18-20. Additionally, the invention facilitate anatomical location of diseased abnormal tissue within normal tissue. This anatomical information is useful in many ways. An example of one important use would be to direct real time WO~a/3266a 2 1 9 1 3 1 2 PCT~Sg5/06'07 therapy. Often abnormal myocardial tissue causes deleterious rhythm disturbances. Unfortunately, this abnormal tissue may be visually indistinguishable from surrounding normal myocardium. The present invention provides real time imaging of the abnormal tissue based on the dielectric characteristic differences such as those detected in Figures 18-20.
Using fast reconstruction routines and scanning through the frequency range in at time rates that are fractions of the tissue event time cycle, a clinician creates a map of the abnormal tissue. Depending upon which frequency and dielectric characteristic is evaluated, the investigator may reconstruct the dielectric properties to generate a functional excitation map through the abnormal tissue area or alternatively may reconstruct a temporal change map and correlate those temporal changes to known electrical markers for anomalies within the tissue. The clinician may then direct ablation therapy to remove this abnormal rhythm focus and evaluate the adequacy of the tissue removal.
An embodiment of the present invention using laser or microwave sources of ablation is disclosed in Figure 21. As disclosed, a method for ablation of a lesion, for example, an arrhythmogenic focus within normal myocardial tissue, is performed beginning with inputing information into an input data formation step 300 from anatomical structure analysis derived from data generated by the invention disclosed in Figure 2 and expected temperature distribution values. The input data formation step uses information from a microwave power source as an approximation step 302 or a laser power source as an approximation step 304 to derive input to be fed to a direct problem solution for microwave 306 or direct problem solution for laser control 308. A determination step for determining the possible available microwave and laser power sources is undertaken at step 310. The result of this determination is passed onto a sources and lesions correlation databank 312 to derive an approximation step 314, also taking input from an antenna simulation step 316. The current expected temperature is calculated at step 318 and corrected for a temperature non-linearity at step 320. The results of the direct problem -wo ss/3266s 2 ~ 9 1 3 1 2 PCTIUS95/06507 solutions for microwave or laser 306, 308 in conjunction with the corrected current temperature from 320 is incorporated into a biological heat equation solution 322 to derive an actual temperature solution.
Temperature distribution from the bioequation step 322 is passed to a lesion localization step 324 which provides data back to the source lesion correlation databank 312 for running the next approximation through to the input data formation 300 for the next determination of the bioheat equation solution step 322. Information from the equation solution step 322 is also passed to a different necessary lesion current lesion formation step for comparing the current lesion size with the estimated necessary lesion size to determine if optimum therapy has been achieved or not. If treatment has been achieved, the decision then passes to optimal region step 328. If the current lesion is different than the necessary lesion, the different information is passed back to step sources lesion correlation databank 312 for a reapproximation at step 314 on through input data formation 300 to undertake the next treatment in order to more closely approximate the necessary lesion through treatment. The number of steps through the iterative process are monitored by switch 330 with comparison of an expected location size of lesion step 332 at step 0, step 334.
For steps greater than 0, switch 330 switches to step greater than zero step 336. The entire process is continuously re-evaluated for completeness of ablation therapy and re-evaluating on a real time basis the lesion generated by analysis of the anatomical structure derived from the microwave tomographic imaging system.
The invention provides for using microwave energy in a novel approach providing rapid real time assessment of biological function and anatomical structure by reverse problem solution for the dielectric characteristics of biological tissues. The invention achieves substantial increase in processing speed as well as substantial improvement in resolving power over any known prior art. The present invention also provides for techniques in evaluating real time parameters for determining biological component concentrations or physiologic ~ - .
u 0 95132665 2 ~ 9 1 3 1 2 PCT/US95106507 characteristics based on the dielectric contrast between different states of physiologic activity for the biological compound or physiologic reaction.
Claims (39)
1. A system for non-invasive microwave tomographic spectroscopy of tissue, the system comprising:
a) power source means for supplying microwave radiation;
b) a plurality of microwave emitter-receivers spatially oriented to the tissue;
c) an interface medium placed between the emitter-receivers;
d) control means operably coupled between the power source means and the plurality of microwave emitter-receivers for selectively controlling power to the plurality of emitter-receivers and for receiving microwave signals from the plurality of emitter-receivers so that multiple frequency microwave radiation is emitted from a selected plurality of emitter-receivers and received by a selected plurality of emitter-receivers after interacting with and passing through the tissue; and e) computational means operably connected to the control means for computing a tomographic spectroscopic image of the tissue from the microwave signals received from the selected plurality of emitter-receivers.
a) power source means for supplying microwave radiation;
b) a plurality of microwave emitter-receivers spatially oriented to the tissue;
c) an interface medium placed between the emitter-receivers;
d) control means operably coupled between the power source means and the plurality of microwave emitter-receivers for selectively controlling power to the plurality of emitter-receivers and for receiving microwave signals from the plurality of emitter-receivers so that multiple frequency microwave radiation is emitted from a selected plurality of emitter-receivers and received by a selected plurality of emitter-receivers after interacting with and passing through the tissue; and e) computational means operably connected to the control means for computing a tomographic spectroscopic image of the tissue from the microwave signals received from the selected plurality of emitter-receivers.
2. The system of claim 1 in which the interface medium comprises a fluid having a preliminary dielectrically adjustable dielectric permittivity between about 50 and 90 at 2.45 GHz and a dielectric loss between about 5 and 25.
3. The system of claim 1 in which the multiple frequency microwave radiation is preferably within the range of about 0.2 GHz to about 5 GHz.
4. The system of claim 1 in which the multiple frequencies of microwave radiation are generated using pulse width emissions from one of the emitters, each emission having a power level of about 1 mW/cm.
5. The system of claim 1 in which the plurality of microwave emitter-receivers comprises an array of emitter-receivers arranged in a circular configuration.
6. The system of claim 5 in which the emitter-receivers are radially adjustable relative to the circular array.
7. The system of claim 1 in which the plurality of microwave emitter-receivers comprises a plurality of stacked emitter-receivers arranged in a circular configuration.
8. The system of claim 1 in which the control means comprises means for selecting a multiple of emitter-receivers to act as emitters and a separate multiple of emitter-receivers to act as receivers.
9. The system of claim 1 in which the computational means comprises:
an input data formation component;
a direct problem solution component;
a reverse problem solution component; and a frequency correlation component.
an input data formation component;
a direct problem solution component;
a reverse problem solution component; and a frequency correlation component.
10. The system of claim 9 in which the reverse problem solution component comprises:
a functional formation component;
a gradient formation component;
a minimization parameter tau calculation component; and an .epsilon.* calculation.
a functional formation component;
a gradient formation component;
a minimization parameter tau calculation component; and an .epsilon.* calculation.
11. The system of claim 1 further comprising encoding means for encoding the microwave radiation supplied to the selected plurality of emitter-receivers for projection so that when the microwave signals are received from the selected receiving plurality of emitter-receivers after interacting with the tissue, the signals are distinguishable by their originating emitter.
12. The system of claim 11 in which the encoding means comprises means for altering the microwave radiation phase.
13. The system of claim 11 in which the encoding means comprises means for altering the microwave radiation amplitude.
14. The system of claim 11 in which the encoding means comprises means for altering the microwave radiation polarity.
15. The system of claim 10 in which the .epsilon.* calculation is a value derived by calculating dielectric characteristics, .epsilon.' and .epsilon.", derived from the measured differences in the amplitude and phase changes of emitted and received microwave energy across a specified frequency range.
16. A method for non-invasive microwave tomographic spectroscopy of tissue, the method comprising the steps of:
a) providing a microwave radiation power source;
b) providing a plurality of microwave radiation emitter-receivers;
c) controlling the plurality of microwave radiation emitter-receivers so that a plurality of emitter-receivers are able to emit multiple microwave frequency radiation from the power source to a plurality of emitter-receivers that are receiving the microwave radiation;
d) placing an interface medium between the emitting and receiving microwave emitter-receivers;
e) placing tissue to be irradiated within the interface medium;
f) emitting the microwave radiation from the microwave emitter-receivers;
g) receiving the microwave radiation in the microwave emitter-receivers after interacting with the tissue; and h) measuring a change in the microwave radiation after interacting with the tissue.
a) providing a microwave radiation power source;
b) providing a plurality of microwave radiation emitter-receivers;
c) controlling the plurality of microwave radiation emitter-receivers so that a plurality of emitter-receivers are able to emit multiple microwave frequency radiation from the power source to a plurality of emitter-receivers that are receiving the microwave radiation;
d) placing an interface medium between the emitting and receiving microwave emitter-receivers;
e) placing tissue to be irradiated within the interface medium;
f) emitting the microwave radiation from the microwave emitter-receivers;
g) receiving the microwave radiation in the microwave emitter-receivers after interacting with the tissue; and h) measuring a change in the microwave radiation after interacting with the tissue.
17. The method of claim 16 further comprising the steps of:
encoding the emitted microwave radiation to distinguish an origin among the different emitters of the plurality of emitter-receivers; and decoding the received microwave radiation after interacting with the tissue so that the changed microwave radiation is distinguishable by the originating emitter.
encoding the emitted microwave radiation to distinguish an origin among the different emitters of the plurality of emitter-receivers; and decoding the received microwave radiation after interacting with the tissue so that the changed microwave radiation is distinguishable by the originating emitter.
18. The method of claim 16 in which the multiple frequency microwave radiation is simultaneously emitted from a plurality of emitters.
19. The method of claim 16 in which the measuring step includes solving the reverse problem to compute a tomographic image of the tissue based on the measured change of the microwave radiation, the reverse problem solution comprising the steps of:
a) determining a functional formation component;
b) using a gradient formation component;
c) calculating a minimization parameter tau; and d) performing an .epsilon.* calculation.
a) determining a functional formation component;
b) using a gradient formation component;
c) calculating a minimization parameter tau; and d) performing an .epsilon.* calculation.
20. A method of identifying discrete signals correlating to specific antenna arrays in a microwave tomographic spectroscopy tissue imaging system, comprising the steps of:
a) providing a microwave tomographic spectroscopy system having a microwave power source, a plurality of microwave emitters-receivers, an interface medium between the microwave emitters-receivers, control means for providing microwave signals to the emitters-receivers and for receiving microwave signals from the emitters-receivers after the microwave signals have interacted with the tissue;
b) orienting a tissue to be imaged in the interface medium;
c) encoding the signals originating simultaneously from different emitters and interacting with the tissue; and d) decoding the signals received by different receivers so that the signals are distinguishable according to the originating emitter.
a) providing a microwave tomographic spectroscopy system having a microwave power source, a plurality of microwave emitters-receivers, an interface medium between the microwave emitters-receivers, control means for providing microwave signals to the emitters-receivers and for receiving microwave signals from the emitters-receivers after the microwave signals have interacted with the tissue;
b) orienting a tissue to be imaged in the interface medium;
c) encoding the signals originating simultaneously from different emitters and interacting with the tissue; and d) decoding the signals received by different receivers so that the signals are distinguishable according to the originating emitter.
21. The method of claim 20 in which the step of encoding comprises changing the phase of the microwave radiation.
22. The method of claim 20 in which the step of encoding comprises changing the amplitude of the microwave radiation.
23. The method of claim 20 in which the step of encoding comprises changing the polarization of the microwave radiation.
24. The method of claim 20 in which the step of encoding comprises changing the frequency of the microwave radiation.
25. A method of non-invasive microwave tomographic spectroscopy of tissue, the method comprising the steps of:
a) designating a target tissue area for microwave irradiation;
b) determining expected tissue dielectric values for the designated target tissue area;
c) providing a multiple frequency microwave radiation emitting and receiving system having microwave emission means, microwave receiving means and microwave analysis means;
d) irradiating the target tissue area with microwave radiation from the microwave emission means;
e) receiving the microwave radiation from the irradiated target tissue area with the receiving means;
f) analyzing the received microwave radiation with the analysis means to obtain observed tissue dielectric values; and g) comparing the observed tissue dielectric values with the expected tissue dielectric values to determine a physiologic state of the tissue within the designated target tissue area.
a) designating a target tissue area for microwave irradiation;
b) determining expected tissue dielectric values for the designated target tissue area;
c) providing a multiple frequency microwave radiation emitting and receiving system having microwave emission means, microwave receiving means and microwave analysis means;
d) irradiating the target tissue area with microwave radiation from the microwave emission means;
e) receiving the microwave radiation from the irradiated target tissue area with the receiving means;
f) analyzing the received microwave radiation with the analysis means to obtain observed tissue dielectric values; and g) comparing the observed tissue dielectric values with the expected tissue dielectric values to determine a physiologic state of the tissue within the designated target tissue area.
26. The method of claim 25 in which the multiple frequency microwave radiation is simultaneously emitted from a plurality of emitters.
27. The method of claim 25 in which the analyzing and comparing steps include solving the reverse problem to compute a tomographic image of the tissue based on the measured change of the microwave radiation, the reverse problem solution comprising the steps of:
a) determining a functional formation component;
b) using a gradient formation component;
c) calculating a minimization parameter tau; and d) performing an E* calculation.
a) determining a functional formation component;
b) using a gradient formation component;
c) calculating a minimization parameter tau; and d) performing an E* calculation.
28. The method of claim 25 in which the providing the microwave radiation emitting step comprises providing microwave radiation in multiple frequencies.
29. The method of claim 25 in which the comparing step comprises comparing the received microwave radiation in real time permitting real time determining of a changing physiologic state.
30. The method of claim 25 in which the determined physiologic state is a physiologic state selected from the list of physiologic states consisting of temperature, electrical excitation state, oxyhemoglobin saturation, blood oxygen content, total hemoglobin, and blood gas partial pressures.
31. The method of claim 30 in which the blood gas partial pressures include PO2.
32. The method of claim 25 in which the designated target tissue area includes a patient's cardiac region to locate the origin of cardiac arrhythmias.
33. The method of claim 25 in which the step of providing a multiple frequency microwave radiation emitting and receiving system includes use of in vivo and in vitro subsystems.
34. The method of claim 33 comprising use of a catheter ablation energy delivery subsystem.
35. The method of claim 16, 20, or 25 further comprising the step of ablating designated tissue regions using an ablation catheter subsystem.
36. The method of claim 35 in which the ablation catheter subsystem uses laser energy for ablation.
37. The method of claim 35 in which the ablation catheter subsystem uses microwave energy for ablation.
38. The method of claim 35 in which the ablation catheter subsystem uses radio frequency energy for ablation.
39. A tomographic spectroscopic image generated using the method of claim 16, 20, or 25.
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US08/250,762 US5715819A (en) | 1994-05-26 | 1994-05-26 | Microwave tomographic spectroscopy system and method |
US08/250,762 | 1994-05-26 |
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EP (1) | EP0762847A4 (en) |
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Cited By (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
WO2016005909A1 (en) * | 2014-07-07 | 2016-01-14 | University Of Manitoba | Imaging using reconfigurable antennas |
Families Citing this family (175)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US6380751B2 (en) * | 1992-06-11 | 2002-04-30 | Cascade Microtech, Inc. | Wafer probe station having environment control enclosure |
US5345170A (en) * | 1992-06-11 | 1994-09-06 | Cascade Microtech, Inc. | Wafer probe station having integrated guarding, Kelvin connection and shielding systems |
SE501473C2 (en) | 1993-02-03 | 1995-02-27 | Stiftelsen Metallurg Forsk | Ways of determining the state of gases and flames in melt and combustion processes |
US6232789B1 (en) * | 1997-05-28 | 2001-05-15 | Cascade Microtech, Inc. | Probe holder for low current measurements |
US5561377A (en) * | 1995-04-14 | 1996-10-01 | Cascade Microtech, Inc. | System for evaluating probing networks |
US6876878B2 (en) * | 1996-06-26 | 2005-04-05 | University Of Utah Research Foundation | Medical broad band electromagnetic holographic imaging |
EP0928157B1 (en) * | 1996-07-05 | 2004-06-09 | The Carolinas Heart Institute | Electromagnetic imaging and therapeutic (emit) systems |
US6026173A (en) * | 1997-07-05 | 2000-02-15 | Svenson; Robert H. | Electromagnetic imaging and therapeutic (EMIT) systems |
US5914613A (en) * | 1996-08-08 | 1999-06-22 | Cascade Microtech, Inc. | Membrane probing system with local contact scrub |
CN1261259A (en) * | 1997-05-23 | 2000-07-26 | 卡罗莱纳心脏研究所 | Electromagnetical imaging and therpeutic (Emit) systems |
US6002263A (en) * | 1997-06-06 | 1999-12-14 | Cascade Microtech, Inc. | Probe station having inner and outer shielding |
US7550969B2 (en) * | 1997-06-26 | 2009-06-23 | University Of Utah Research Foundation | Security screening and inspection based on broadband electromagnetic holographic imaging |
US6256882B1 (en) | 1998-07-14 | 2001-07-10 | Cascade Microtech, Inc. | Membrane probing system |
US6097985A (en) * | 1999-02-09 | 2000-08-01 | Kai Technologies, Inc. | Microwave systems for medical hyperthermia, thermotherapy and diagnosis |
US6233490B1 (en) | 1999-02-09 | 2001-05-15 | Kai Technologies, Inc. | Microwave antennas for medical hyperthermia, thermotherapy and diagnosis |
US6275738B1 (en) * | 1999-08-19 | 2001-08-14 | Kai Technologies, Inc. | Microwave devices for medical hyperthermia, thermotherapy and diagnosis |
US6891381B2 (en) * | 1999-12-30 | 2005-05-10 | Secure Logistix | Human body: scanning, typing and profiling system |
SE517701C2 (en) * | 2000-08-31 | 2002-07-02 | October Biometrics Ab | Device, method and system for measuring distrubution of selected properties in a material |
US6965226B2 (en) * | 2000-09-05 | 2005-11-15 | Cascade Microtech, Inc. | Chuck for holding a device under test |
US6914423B2 (en) * | 2000-09-05 | 2005-07-05 | Cascade Microtech, Inc. | Probe station |
DE10143173A1 (en) | 2000-12-04 | 2002-06-06 | Cascade Microtech Inc | Wafer probe has contact finger array with impedance matching network suitable for wide band |
US6970634B2 (en) * | 2001-05-04 | 2005-11-29 | Cascade Microtech, Inc. | Fiber optic wafer probe |
WO2003052435A1 (en) | 2001-08-21 | 2003-06-26 | Cascade Microtech, Inc. | Membrane probing system |
US6777964B2 (en) * | 2002-01-25 | 2004-08-17 | Cascade Microtech, Inc. | Probe station |
US7352258B2 (en) * | 2002-03-28 | 2008-04-01 | Cascade Microtech, Inc. | Waveguide adapter for probe assembly having a detachable bias tee |
US20040077943A1 (en) * | 2002-04-05 | 2004-04-22 | Meaney Paul M. | Systems and methods for 3-D data acquisition for microwave imaging |
US7164105B2 (en) * | 2002-04-05 | 2007-01-16 | Microwave Imaging Systems Technologies, Inc. | Non-invasive microwave analysis systems |
WO2003098234A2 (en) * | 2002-05-17 | 2003-11-27 | Mr Instruments, Inc. | A cavity resonator for mr systems |
DE10226845A1 (en) * | 2002-06-16 | 2004-01-08 | Otto-Von-Guericke-Universität Magdeburg | Complex permittivity measurement unit uses multiple cavity resonances |
US20040104268A1 (en) * | 2002-07-30 | 2004-06-03 | Bailey Kenneth Stephen | Plug in credit card reader module for wireless cellular phone verifications |
US6847219B1 (en) * | 2002-11-08 | 2005-01-25 | Cascade Microtech, Inc. | Probe station with low noise characteristics |
US7239731B1 (en) * | 2002-11-26 | 2007-07-03 | Emimaging Ltd | System and method for non-destructive functional imaging and mapping of electrical excitation of biological tissues using electromagnetic field tomography and spectroscopy |
US6861856B2 (en) * | 2002-12-13 | 2005-03-01 | Cascade Microtech, Inc. | Guarded tub enclosure |
US7825667B2 (en) * | 2003-04-04 | 2010-11-02 | Microwave Imaging Systems Technologies, Inc. | Microwave imaging system and processes, and associated software products |
US7221172B2 (en) * | 2003-05-06 | 2007-05-22 | Cascade Microtech, Inc. | Switched suspended conductor and connection |
US7057404B2 (en) | 2003-05-23 | 2006-06-06 | Sharp Laboratories Of America, Inc. | Shielded probe for testing a device under test |
US7492172B2 (en) * | 2003-05-23 | 2009-02-17 | Cascade Microtech, Inc. | Chuck for holding a device under test |
JP2007504910A (en) | 2003-09-12 | 2007-03-08 | ミノウ・メディカル・エルエルシイ | Selectable biased reshaping and / or excision of atherosclerotic material |
US7250626B2 (en) * | 2003-10-22 | 2007-07-31 | Cascade Microtech, Inc. | Probe testing structure |
JP2007517231A (en) | 2003-12-24 | 2007-06-28 | カスケード マイクロテック インコーポレイテッド | Active wafer probe |
US7187188B2 (en) * | 2003-12-24 | 2007-03-06 | Cascade Microtech, Inc. | Chuck with integrated wafer support |
US20050264303A1 (en) * | 2004-02-12 | 2005-12-01 | Bailey Kenneth S | Radiation monitoring of body part sizing and use of such sizing for person monitoring |
WO2005122061A2 (en) * | 2004-02-12 | 2005-12-22 | Celunet, Inc. | Radiation monitoring of body part sizing and use of such sizing for person monitoring |
DE202005021434U1 (en) * | 2004-06-07 | 2008-03-20 | Cascade Microtech, Inc., Beaverton | Thermo-optical clamping device |
JP4980903B2 (en) * | 2004-07-07 | 2012-07-18 | カスケード マイクロテック インコーポレイテッド | Probe head with membrane suspension probe |
US7616797B2 (en) * | 2004-08-23 | 2009-11-10 | Bailey Kenneth S | Minutia detection from measurement of a human skull and identifying and profiling individuals from the human skull detection |
US9713730B2 (en) | 2004-09-10 | 2017-07-25 | Boston Scientific Scimed, Inc. | Apparatus and method for treatment of in-stent restenosis |
US8396548B2 (en) | 2008-11-14 | 2013-03-12 | Vessix Vascular, Inc. | Selective drug delivery in a lumen |
JP2008512680A (en) | 2004-09-13 | 2008-04-24 | カスケード マイクロテック インコーポレイテッド | Double-sided probing structure |
US7656172B2 (en) | 2005-01-31 | 2010-02-02 | Cascade Microtech, Inc. | System for testing semiconductors |
US7535247B2 (en) | 2005-01-31 | 2009-05-19 | Cascade Microtech, Inc. | Interface for testing semiconductors |
US20060169897A1 (en) * | 2005-01-31 | 2006-08-03 | Cascade Microtech, Inc. | Microscope system for testing semiconductors |
US7449899B2 (en) * | 2005-06-08 | 2008-11-11 | Cascade Microtech, Inc. | Probe for high frequency signals |
JP5080459B2 (en) * | 2005-06-13 | 2012-11-21 | カスケード マイクロテック インコーポレイテッド | Wideband active / passive differential signal probe |
US7725167B2 (en) * | 2005-07-13 | 2010-05-25 | Clemson University | Microwave imaging assisted ultrasonically |
JP4803529B2 (en) * | 2005-08-31 | 2011-10-26 | 国立大学法人 長崎大学 | Mammography method using microwave and mammography apparatus |
US7659719B2 (en) * | 2005-11-25 | 2010-02-09 | Mr Instruments, Inc. | Cavity resonator for magnetic resonance systems |
GB2434872A (en) * | 2006-02-03 | 2007-08-08 | Christopher Paul Hancock | Microwave system for locating inserts in biological tissue |
EP2011081B1 (en) * | 2006-04-20 | 2018-11-07 | Koninklijke Philips N.V. | Method of motion correction for dynamic volume alignment without timing restrictions |
US8019435B2 (en) | 2006-05-02 | 2011-09-13 | Boston Scientific Scimed, Inc. | Control of arterial smooth muscle tone |
US7520667B2 (en) * | 2006-05-11 | 2009-04-21 | John Bean Technologies Ab | Method and system for determining process parameters |
US7403028B2 (en) | 2006-06-12 | 2008-07-22 | Cascade Microtech, Inc. | Test structure and probe for differential signals |
US7764072B2 (en) * | 2006-06-12 | 2010-07-27 | Cascade Microtech, Inc. | Differential signal probing system |
US7723999B2 (en) | 2006-06-12 | 2010-05-25 | Cascade Microtech, Inc. | Calibration structures for differential signal probing |
US20080012578A1 (en) * | 2006-07-14 | 2008-01-17 | Cascade Microtech, Inc. | System for detecting molecular structure and events |
FR2906369B1 (en) * | 2006-09-25 | 2009-03-06 | Satimo Sa | MICROWAVE DEVICE FOR CONTROLLING A MATERIAL |
EP2954868A1 (en) | 2006-10-18 | 2015-12-16 | Vessix Vascular, Inc. | Tuned rf energy and electrical tissue characterization for selective treatment of target tissues |
AU2007310991B2 (en) | 2006-10-18 | 2013-06-20 | Boston Scientific Scimed, Inc. | System for inducing desirable temperature effects on body tissue |
WO2008049082A2 (en) | 2006-10-18 | 2008-04-24 | Minnow Medical, Inc. | Inducing desirable temperature effects on body tissue |
RU2465826C2 (en) * | 2006-12-15 | 2012-11-10 | Конинклейке Филипс Электроникс Н.В. | X-ray imager with spectral resolution |
GB2445758A (en) * | 2007-01-17 | 2008-07-23 | Univ Hospital Of North Staffor | Intraoperative electromagnetic apparatus and related technology |
CN101668480B (en) * | 2007-04-26 | 2012-10-10 | 皇家飞利浦电子股份有限公司 | Localization system |
US7876114B2 (en) | 2007-08-08 | 2011-01-25 | Cascade Microtech, Inc. | Differential waveguide probe |
US7888957B2 (en) * | 2008-10-06 | 2011-02-15 | Cascade Microtech, Inc. | Probing apparatus with impedance optimized interface |
CN102196773B (en) * | 2008-10-23 | 2013-09-25 | 皇家飞利浦电子股份有限公司 | Molecular imaging |
WO2010049834A1 (en) * | 2008-10-31 | 2010-05-06 | Koninklijke Philips Electronics, N.V. | Method and system of electromagnetic tracking in a medical procedure |
GB0820689D0 (en) * | 2008-11-12 | 2008-12-17 | Siemens Ag | Antenna arrangement |
CN102271603A (en) | 2008-11-17 | 2011-12-07 | 明诺医学股份有限公司 | Selective accumulation of energy with or without knowledge of tissue topography |
WO2010059247A2 (en) | 2008-11-21 | 2010-05-27 | Cascade Microtech, Inc. | Replaceable coupon for a probing apparatus |
US8319503B2 (en) | 2008-11-24 | 2012-11-27 | Cascade Microtech, Inc. | Test apparatus for measuring a characteristic of a device under test |
GB0915491D0 (en) | 2009-09-04 | 2009-10-07 | Univ Keele | Electromagnetic tomography apparatuses and methods |
US9167985B2 (en) * | 2010-03-19 | 2015-10-27 | University Of Manitoba | Microwave tomography systems and methods |
EP2555699B1 (en) | 2010-04-09 | 2019-04-03 | Vessix Vascular, Inc. | Power generating and control apparatus for the treatment of tissue |
US9192790B2 (en) | 2010-04-14 | 2015-11-24 | Boston Scientific Scimed, Inc. | Focused ultrasonic renal denervation |
US8717430B2 (en) | 2010-04-26 | 2014-05-06 | Medtronic Navigation, Inc. | System and method for radio-frequency imaging, registration, and localization |
CN103068302B (en) * | 2010-05-13 | 2016-09-07 | 合理医疗创新有限公司 | Use the method and system of distributed electromagnetic (EM) tissue monitoring |
US8473067B2 (en) | 2010-06-11 | 2013-06-25 | Boston Scientific Scimed, Inc. | Renal denervation and stimulation employing wireless vascular energy transfer arrangement |
US9724010B2 (en) | 2010-07-08 | 2017-08-08 | Emtensor Gmbh | Systems and methods of 4D electromagnetic tomographic (EMT) differential (dynamic) fused imaging |
US9084609B2 (en) | 2010-07-30 | 2015-07-21 | Boston Scientific Scime, Inc. | Spiral balloon catheter for renal nerve ablation |
US9155589B2 (en) | 2010-07-30 | 2015-10-13 | Boston Scientific Scimed, Inc. | Sequential activation RF electrode set for renal nerve ablation |
US9408661B2 (en) | 2010-07-30 | 2016-08-09 | Patrick A. Haverkost | RF electrodes on multiple flexible wires for renal nerve ablation |
US9358365B2 (en) | 2010-07-30 | 2016-06-07 | Boston Scientific Scimed, Inc. | Precision electrode movement control for renal nerve ablation |
US9463062B2 (en) | 2010-07-30 | 2016-10-11 | Boston Scientific Scimed, Inc. | Cooled conductive balloon RF catheter for renal nerve ablation |
CN102397056B (en) * | 2010-09-07 | 2015-10-28 | 华东师范大学 | Difference in dielectric constant distribution detection method in a kind of microwave near-field space exploration |
CN106377312B (en) | 2010-10-25 | 2019-12-10 | 美敦力Af卢森堡有限责任公司 | Microwave catheter apparatus, systems, and methods for renal neuromodulation |
US8974451B2 (en) | 2010-10-25 | 2015-03-10 | Boston Scientific Scimed, Inc. | Renal nerve ablation using conductive fluid jet and RF energy |
US9220558B2 (en) | 2010-10-27 | 2015-12-29 | Boston Scientific Scimed, Inc. | RF renal denervation catheter with multiple independent electrodes |
US9028485B2 (en) | 2010-11-15 | 2015-05-12 | Boston Scientific Scimed, Inc. | Self-expanding cooling electrode for renal nerve ablation |
US9668811B2 (en) | 2010-11-16 | 2017-06-06 | Boston Scientific Scimed, Inc. | Minimally invasive access for renal nerve ablation |
US9089350B2 (en) | 2010-11-16 | 2015-07-28 | Boston Scientific Scimed, Inc. | Renal denervation catheter with RF electrode and integral contrast dye injection arrangement |
US9326751B2 (en) | 2010-11-17 | 2016-05-03 | Boston Scientific Scimed, Inc. | Catheter guidance of external energy for renal denervation |
US9060761B2 (en) | 2010-11-18 | 2015-06-23 | Boston Scientific Scime, Inc. | Catheter-focused magnetic field induced renal nerve ablation |
US9023034B2 (en) | 2010-11-22 | 2015-05-05 | Boston Scientific Scimed, Inc. | Renal ablation electrode with force-activatable conduction apparatus |
US9192435B2 (en) | 2010-11-22 | 2015-11-24 | Boston Scientific Scimed, Inc. | Renal denervation catheter with cooled RF electrode |
EP2457508B1 (en) * | 2010-11-24 | 2014-05-21 | eesy-id GmbH | Recording device for recording a blood count parameter |
US20120157993A1 (en) | 2010-12-15 | 2012-06-21 | Jenson Mark L | Bipolar Off-Wall Electrode Device for Renal Nerve Ablation |
US9220561B2 (en) | 2011-01-19 | 2015-12-29 | Boston Scientific Scimed, Inc. | Guide-compatible large-electrode catheter for renal nerve ablation with reduced arterial injury |
WO2013005134A2 (en) | 2011-07-01 | 2013-01-10 | University Of Manitoba | Imaging using probes |
AU2012283908B2 (en) | 2011-07-20 | 2017-02-16 | Boston Scientific Scimed, Inc. | Percutaneous devices and methods to visualize, target and ablate nerves |
AU2012287189B2 (en) | 2011-07-22 | 2016-10-06 | Boston Scientific Scimed, Inc. | Nerve modulation system with a nerve modulation element positionable in a helical guide |
US9186210B2 (en) | 2011-10-10 | 2015-11-17 | Boston Scientific Scimed, Inc. | Medical devices including ablation electrodes |
US9420955B2 (en) | 2011-10-11 | 2016-08-23 | Boston Scientific Scimed, Inc. | Intravascular temperature monitoring system and method |
WO2013055815A1 (en) | 2011-10-11 | 2013-04-18 | Boston Scientific Scimed, Inc. | Off -wall electrode device for nerve modulation |
US9364284B2 (en) | 2011-10-12 | 2016-06-14 | Boston Scientific Scimed, Inc. | Method of making an off-wall spacer cage |
EP2768568B1 (en) | 2011-10-18 | 2020-05-06 | Boston Scientific Scimed, Inc. | Integrated crossing balloon catheter |
EP2768563B1 (en) | 2011-10-18 | 2016-11-09 | Boston Scientific Scimed, Inc. | Deflectable medical devices |
CN104023662B (en) | 2011-11-08 | 2018-02-09 | 波士顿科学西美德公司 | Hole portion renal nerve melts |
US9119600B2 (en) | 2011-11-15 | 2015-09-01 | Boston Scientific Scimed, Inc. | Device and methods for renal nerve modulation monitoring |
US9119632B2 (en) | 2011-11-21 | 2015-09-01 | Boston Scientific Scimed, Inc. | Deflectable renal nerve ablation catheter |
TWI467184B (en) * | 2011-12-20 | 2015-01-01 | Univ Nat Cheng Kung | Spectrum analysis method and disease examination method |
US9265969B2 (en) | 2011-12-21 | 2016-02-23 | Cardiac Pacemakers, Inc. | Methods for modulating cell function |
EP3138521B1 (en) | 2011-12-23 | 2019-05-29 | Vessix Vascular, Inc. | Apparatuses for remodeling tissue of or adjacent to a body passage |
US9433760B2 (en) | 2011-12-28 | 2016-09-06 | Boston Scientific Scimed, Inc. | Device and methods for nerve modulation using a novel ablation catheter with polymeric ablative elements |
US9050106B2 (en) | 2011-12-29 | 2015-06-09 | Boston Scientific Scimed, Inc. | Off-wall electrode device and methods for nerve modulation |
WO2013169927A1 (en) | 2012-05-08 | 2013-11-14 | Boston Scientific Scimed, Inc. | Renal nerve modulation devices |
WO2014032016A1 (en) | 2012-08-24 | 2014-02-27 | Boston Scientific Scimed, Inc. | Intravascular catheter with a balloon comprising separate microporous regions |
CN104780859B (en) | 2012-09-17 | 2017-07-25 | 波士顿科学西美德公司 | Self-positioning electrode system and method for renal regulation |
WO2014047454A2 (en) | 2012-09-21 | 2014-03-27 | Boston Scientific Scimed, Inc. | Self-cooling ultrasound ablation catheter |
WO2014047411A1 (en) | 2012-09-21 | 2014-03-27 | Boston Scientific Scimed, Inc. | System for nerve modulation and innocuous thermal gradient nerve block |
US10835305B2 (en) | 2012-10-10 | 2020-11-17 | Boston Scientific Scimed, Inc. | Renal nerve modulation devices and methods |
CA2936145C (en) | 2012-11-21 | 2021-06-15 | Emtensor Gmbh | Electromagnetic tomography solutions for scanning head |
EP2957925B1 (en) * | 2013-02-12 | 2016-11-23 | National University Corporation Kobe University | Scattering tomography method and scattering tomography device |
WO2014163987A1 (en) | 2013-03-11 | 2014-10-09 | Boston Scientific Scimed, Inc. | Medical devices for modulating nerves |
US9693821B2 (en) | 2013-03-11 | 2017-07-04 | Boston Scientific Scimed, Inc. | Medical devices for modulating nerves |
US9808311B2 (en) | 2013-03-13 | 2017-11-07 | Boston Scientific Scimed, Inc. | Deflectable medical devices |
JP6220044B2 (en) | 2013-03-15 | 2017-10-25 | ボストン サイエンティフィック サイムド,インコーポレイテッドBoston Scientific Scimed,Inc. | Medical device for renal nerve ablation |
AU2014237950B2 (en) | 2013-03-15 | 2017-04-13 | Boston Scientific Scimed, Inc. | Control unit for use with electrode pads and a method for estimating an electrical leakage |
US20140275944A1 (en) | 2013-03-15 | 2014-09-18 | Emtensor Gmbh | Handheld electromagnetic field-based bio-sensing and bio-imaging system |
US10265122B2 (en) | 2013-03-15 | 2019-04-23 | Boston Scientific Scimed, Inc. | Nerve ablation devices and related methods of use |
US9072449B2 (en) | 2013-03-15 | 2015-07-07 | Emtensor Gmbh | Wearable/man-portable electromagnetic tomographic imaging |
EP2968919B1 (en) | 2013-03-15 | 2021-08-25 | Medtronic Ardian Luxembourg S.à.r.l. | Controlled neuromodulation systems |
WO2014205388A1 (en) | 2013-06-21 | 2014-12-24 | Boston Scientific Scimed, Inc. | Renal denervation balloon catheter with ride along electrode support |
WO2014205399A1 (en) | 2013-06-21 | 2014-12-24 | Boston Scientific Scimed, Inc. | Medical devices for renal nerve ablation having rotatable shafts |
US9707036B2 (en) | 2013-06-25 | 2017-07-18 | Boston Scientific Scimed, Inc. | Devices and methods for nerve modulation using localized indifferent electrodes |
EP3016605B1 (en) | 2013-07-01 | 2019-06-05 | Boston Scientific Scimed, Inc. | Medical devices for renal nerve ablation |
US10660698B2 (en) | 2013-07-11 | 2020-05-26 | Boston Scientific Scimed, Inc. | Devices and methods for nerve modulation |
CN105377170A (en) | 2013-07-11 | 2016-03-02 | 波士顿科学国际有限公司 | Medical device with stretchable electrode assemblies |
CN105682594B (en) | 2013-07-19 | 2018-06-22 | 波士顿科学国际有限公司 | Helical bipolar electrodes renal denervation dominates air bag |
WO2015013301A1 (en) | 2013-07-22 | 2015-01-29 | Boston Scientific Scimed, Inc. | Renal nerve ablation catheter having twist balloon |
WO2015013205A1 (en) | 2013-07-22 | 2015-01-29 | Boston Scientific Scimed, Inc. | Medical devices for renal nerve ablation |
WO2015024020A1 (en) | 2013-08-16 | 2015-02-19 | The General Hospital Corporation | Portable diffraction-based imaging and diagnostic systems and methods |
EP4049605A1 (en) | 2013-08-22 | 2022-08-31 | Boston Scientific Scimed Inc. | Flexible circuit having improved adhesion to a renal nerve modulation balloon |
CN105555218B (en) | 2013-09-04 | 2019-01-15 | 波士顿科学国际有限公司 | With radio frequency (RF) foley's tube rinsed with cooling capacity |
CN105530885B (en) | 2013-09-13 | 2020-09-22 | 波士顿科学国际有限公司 | Ablation balloon with vapor deposited covering |
US11246654B2 (en) | 2013-10-14 | 2022-02-15 | Boston Scientific Scimed, Inc. | Flexible renal nerve ablation devices and related methods of use and manufacture |
US9687166B2 (en) | 2013-10-14 | 2017-06-27 | Boston Scientific Scimed, Inc. | High resolution cardiac mapping electrode array catheter |
US9770606B2 (en) | 2013-10-15 | 2017-09-26 | Boston Scientific Scimed, Inc. | Ultrasound ablation catheter with cooling infusion and centering basket |
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WO2016178235A1 (en) * | 2015-05-05 | 2016-11-10 | Vayyar Imaging Ltd | System and methods for three dimensional modeling of an object using a radio frequency device |
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WO2017066731A1 (en) | 2015-10-16 | 2017-04-20 | Emtensor Gmbh | Electromagnetic interference pattern recognition tomography |
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US11300558B2 (en) * | 2018-06-14 | 2022-04-12 | Nokomis, Inc. | Apparatus and system for spectroscopy and tomography of fragile biologic materials |
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RU2769968C1 (en) * | 2022-02-02 | 2022-04-11 | Дмитрий Феоктистович Зайцев | System and method for radiofrequency tomography |
Family Cites Families (11)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US4135131A (en) * | 1977-10-14 | 1979-01-16 | The United States Of America As Represented By The Secretary Of The Army | Microwave time delay spectroscopic methods and apparatus for remote interrogation of biological targets |
US4247815A (en) * | 1979-05-22 | 1981-01-27 | The United States Of America As Represented By The Secretary Of The Army | Method and apparatus for physiologic facsimile imaging of biologic targets based on complex permittivity measurements using remote microwave interrogation |
US4662222A (en) * | 1984-12-21 | 1987-05-05 | Johnson Steven A | Apparatus and method for acoustic imaging using inverse scattering techniques |
DE3531893A1 (en) * | 1985-09-06 | 1987-03-19 | Siemens Ag | METHOD FOR DETERMINING THE DISTRIBUTION OF DIELECTRICITY CONSTANTS IN AN EXAMINATION BODY, AND MEASURING ARRANGEMENT FOR IMPLEMENTING THE METHOD |
DE3601983A1 (en) * | 1986-01-23 | 1987-07-30 | Siemens Ag | METHOD AND DEVICE FOR CONTACTLESS DETERMINATION OF TEMPERATURE DISTRIBUTION IN AN EXAMINATION OBJECT |
US4926868A (en) * | 1987-04-15 | 1990-05-22 | Larsen Lawrence E | Method and apparatus for cardiac hemodynamic monitor |
US5144236A (en) * | 1990-08-17 | 1992-09-01 | Strenk Scientific Consultants, Inc. | Method and apparatus for r.f. tomography |
US5363050A (en) * | 1990-08-31 | 1994-11-08 | Guo Wendy W | Quantitative dielectric imaging system |
US5222501A (en) * | 1992-01-31 | 1993-06-29 | Duke University | Methods for the diagnosis and ablation treatment of ventricular tachycardia |
US5305748A (en) * | 1992-06-05 | 1994-04-26 | Wilk Peter J | Medical diagnostic system and related method |
US5405346A (en) * | 1993-05-14 | 1995-04-11 | Fidus Medical Technology Corporation | Tunable microwave ablation catheter |
-
1994
- 1994-05-26 US US08/250,762 patent/US5715819A/en not_active Expired - Lifetime
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1995
- 1995-05-24 CN CN95193883A patent/CN1123320C/en not_active Expired - Fee Related
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- 1995-05-24 EP EP95922880A patent/EP0762847A4/en not_active Withdrawn
- 1995-05-24 RU RU96124805/14A patent/RU2238033C2/en not_active IP Right Cessation
- 1995-05-24 WO PCT/US1995/006507 patent/WO1995032665A1/en not_active Application Discontinuation
- 1995-05-24 CA CA002191312A patent/CA2191312A1/en not_active Abandoned
-
1996
- 1996-11-26 KR KR1019960706696A patent/KR970703111A/en active IP Right Grant
Cited By (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
WO2016005909A1 (en) * | 2014-07-07 | 2016-01-14 | University Of Manitoba | Imaging using reconfigurable antennas |
US10197508B2 (en) | 2014-07-07 | 2019-02-05 | Univeristy Of Manitoba | Imaging using reconfigurable antennas |
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CN1123320C (en) | 2003-10-08 |
KR970703111A (en) | 1997-07-03 |
AU2761895A (en) | 1995-12-21 |
US5715819A (en) | 1998-02-10 |
CN1151684A (en) | 1997-06-11 |
RU2238033C2 (en) | 2004-10-20 |
EP0762847A4 (en) | 1999-11-03 |
JPH10504893A (en) | 1998-05-12 |
EP0762847A1 (en) | 1997-03-19 |
WO1995032665A1 (en) | 1995-12-07 |
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