Surgery – Diagnostic testing – Detecting nuclear – electromagnetic – or ultrasonic radiation
Reexamination Certificate
1999-10-19
2001-12-18
Casler, Brian L. (Department: 3737)
Surgery
Diagnostic testing
Detecting nuclear, electromagnetic, or ultrasonic radiation
C600S430000, C324S637000
Reexamination Certificate
active
06332087
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to EMIT systems. Specifically, the invention pertains to apparatus and method in which multi-frequency microwave in combination with preferably low frequency is structured to generate a multi-source externally focused microwave for tissue ablation. The invention includes several versions of EMIT systems differentiated on the basis of frequency levels and complexity. Further, the invention includes a computer implemented software specifically configured and tailored to the EMIT system with a graphical and three-dimensional tomographic imaging interface.
BACKGROUND OF THE INVENTION
Electromagnetic tomography is a relatively new technology with enormous potential for use in medical and related industries. Specifically, the technology is becoming prominently mature and practicable for use in internal, non-invasive, real-time imaging of the physiologic properties of tissues and organs, based on tissue dielectric properties differentiation.
Known microwave tomographic imaging utilizes microwave radiation to image an object by detecting the effects the object had on the microwave beam after it has encountered the object. The changes effected in the reflected microwave, due to this encounter, are dependent upon the dielectric permittivity and conductivity properties of the tissues of the object being imaged. Specifically, for a given microwave frequency, the observed changes in the reflected microwave echo signify a specific signature of the imaged tissue.
Microwaves are ultra-high to super-high frequency radio waves with very short wavelengths ranging from approximately 130 centimeters down to fractions of a millimeter. Frequencies range between 0.1 Giga Hertz (GHZ) to 3000 GHZ. The microwave range which is currently used for microwave imaging of biological tissues is in the range of about 0.5 to about 3 GHZ. However, other ranges of the microwave spectrum may also be used as well. The determinant in the selection of the range is that the radiation be non-ionizing to prevent destruction of tissue members or cells. Accordingly, there are biophysical parameters which should be considered when determining a compatible frequency range.
The prior art utilizes two basic categories of microwave imaging. The first category is static imaging based on forming images by determining the 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. The latter form of imaging is extremely useful in applications in imaging biological tissues to monitor ongoing physiological change. Both static and dynamic imaging techniques require an active 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.
Using dynamic imaging, image reconstruction is based on the difference in diffracted fields recorded from several data sets taken from a body with a changing dielectric contrast. However, internal imaging within larger bodies poses resolution problems which limit the application and scope of dynamic imaging. The present invention provides significant advances over the prior art by integrating biophysical, computer software and microwave tomography technologies to provide a high resolution image.
SUMMARY OF THE INVENTION
The invention integrates and implements biophysical, algorithmic/computer and microwave tomography devices and methods to provide a three-dimensional tomographic system. Specifically, the invention includes a new method and system for medical physiological tomography wherein a one frequency three dimensional microwave tomographic system (3D MWT) is combined with a one frequency three dimensional electrical impedance tomographic system (3D EIT) capable of imaging a full scale biological object(s) such as a human torso.
Specifically, the present invention provides a non-invasive real time imaging of the physiologic properties and temporal changes of tissues and organs based on tissue dielectric properties differentiation. For example, using the invention it has been shown that the dielectric properties of the myocardium are sensitive indicators of its physiological condition, including local blood supply, ischemia and infarction. The degree of change in the myocardial dielectric properties provides adequate data for reconstruction using microwave tomography. More specifically, the invention includes an EMIT system with a number of microwave frequencies (microwave spectroscopy) and other frequencies lower than the particular cellular membrane relaxation frequency. This frequency composition of the invention enables estimation of biophysical parameters of the tissue as cellular volume fraction, intracellular and membrane resistivities, cell membrane capacitance, tissue free and bound water content and tissue temperature. It should be noted that such information is critical not only for cardiology but also for other branches of medicine, inter alia, oncology, urology, neurology and other studies.
Further, the present invention provides mathematical models and computer implemented algorithms for constructing heretofore unavailable quantitatively reconstructed clear structural images which depict exact distribution of dielectric properties within an object.
Description of the Preferred Embodiment
The present invention provides a three dimensional microwave tomographic system which is combined with a three dimensional electrical impedance tomographic system. Specifically, the invention includes a one frequency three dimensional microwave tomographic system combined with one frequency three dimensional electrical impedance tomographic system capable of imaging a full scale biological object(s) such as, for example, portions of a human torso. The disclosures of the present invention provide both theoretical and experimental values which show some of the advantages and advances of the invention relative to the physiological imaging prior art currently available in medical diagnosis and therapy.
The present invention contemplates a staged approach in which a first generation EMIT system is launched with possible upgrades to a second generation system. The first generation is distinguished in that it has two systems having the following characteristics (a) Multifrequency microwave spectroscopic tomographic 0.2-6 GHZ, and (b) single microwave frequency (about 0.8 to 1 GHZ) with a single low frequency (about 20 Hz to 200 kHZ). The second generation comprises of three systems with the following distinguishing characteristics: (a) Multifrequency microwave 0.2-6 GHZ, (b) One low frequency approximately 200 kHZ and c) multisource externally focused microwave for tissue ablation (60° C.).
Further, the present invention provides unique algorithm and software to enable the generation of very accurate images from the EMIT systems. Specifically, the algorithms enable image reconstruction from microwave tomography. Since the linear optics approximation used in X-ray tomographic image construction is not readily adaptable to microwave tomography primarily because of electromagnetic wave propagation through biological media involving diffraction and interference phenomenon, there is a need to develop specific algorithms to solve Maxwell equations or their scalar approximation. The present invention provides algorithmic models and software programs to solve these equations and enable a reconstruction of images as needed. Details of the types of models, assumptions, limitations and related mathematical postulations are discussed below. Several structures, features and alternate embodiments are disclosed herein to provide the inventors the protection they are deemed entitled. The invention is multi-faceted and may include several inventions and embodiments which applicants may pursue individually or combine as apparent. Further, it should
Baranov Vladimir
Semenov Serguei Y.
Svenson Robert H.
Casler Brian L.
Fredrikson & Byron , P.A.
The Carolinas Heart Institute
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