Tomographic imaging system and process
Inventors
ABBOSH, Amin • Zamani, Ali • AFSARI, Arman
Assignees
Publication Number
US-11551386-B2
Publication Date
2023-01-10
Expiration Date
2038-05-09
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Abstract
A tomographic imaging system, including a data processing component having a memory and at least one processor configured to: access scattering parameter data representing electromagnetic waves scattered by features within an object and originating from a plurality of antennas disposed around the object on a boundary S;process the scattering parameter data to generate a reconstructed image representing a spatial distribution of features within the object, said processing including:solving an electromagnetic inverse problem, wherein forward and inverse steps of the inverse problem are represented and solved as respective differential equations involving an electric field to determine values for the electric field; andprocess the determined values of the electric field to generate reconstructed image data representing one or more spatial distributions of one or more electromagnetic properties within the object.
Core Innovation
The present invention provides a tomographic imaging system and process that solves electromagnetic inverse problems using partial differential equations rather than integral equations. The process accesses scattering parameter data representing electromagnetic waves scattered by features within an object and originating from a plurality of antennas disposed around the object on a boundary S. It processes this data by solving the electromagnetic inverse problem with forward and inverse steps represented and solved as respective differential equations involving an electric field to determine values for the electric field. These determined electric field values are then processed to generate reconstructed image data representing one or more spatial distributions of one or more electromagnetic properties within the object.
The problem addressed by the invention arises from the inherent limitations of existing electromagnetic inverse problem-solving methods, which rely on integral equations and require approximations such as assuming antennas as ideal point sources, homogeneity along an axis, and the use of a background matching medium. These approximations restrict the reconstructed images to two dimensions and cause errors, and the matching medium causes signal attenuation that reduces dynamic range and detection capability. Moreover, existing methods can be highly time-consuming, making them unsuitable for emergency biomedical imaging scenarios where rapid imaging is critical.
The invention overcomes these shortcomings by formulating the forward and inverse steps of the electromagnetic inverse problem using partial differential equations that can be solved efficiently with numerical methods such as the finite element method. This differential-equation framework allows for accurate three-dimensional image reconstruction without the need for the common approximations of integral-based methods. The approach also includes defining appropriate boundary conditions derived from scattering parameter data at the antennas to regularize the problem and facilitate convergence to a solution.
Claims Coverage
The patent includes a set of independent claims covering processes and systems for tomographic imaging that utilize differential equation-based methods to solve electromagnetic inverse problems and methods to determine object boundaries from antenna measurements. The independent claims disclose inventive features related to the differential equation formulation, processing of scattering parameter data, and boundary determination techniques.
Differential equation-based tomographic imaging process
A tomographic imaging process that accesses scattering parameter data from antennas around an object and processes the data by solving an electromagnetic inverse problem using forward and inverse steps represented and solved as respective differential equations involving an electric field to determine electric field values, which are then used to generate reconstructed image data representing electromagnetic properties within the object.
Estimating permittivity values using regression of scattering parameters
Processing the scattering parameter data includes estimating the permittivity values of the object by using pre-determined training data with regression coefficients representing a quadratic relationship between a function of scattering parameters for different training scattering media and their respective permittivity values.
Inverse and forward step differential equations with boundary conditions
The inverse step is represented by a first-order differential equation involving the divergence of the electric field and permittivity, accompanied by boundary conditions defining permittivity values at the antenna surfaces, dielectric interfaces, and the surrounding boundary S. The forward step is represented by a second-order differential equation with boundary conditions involving continuity of tangential electric fields and normal displacement fields, as well as absorbing boundary conditions.
Determining boundaries of the object from antenna measurements
Including a method to determine the boundary of the object before processing the scattering parameter data, where the boundary determination is based on relationships between distances of the object from the antennas and measured antenna reflection coefficients, resonant frequencies, input impedances, or frequency domain reflection coefficients transformed to time-domain and spatial domain using antenna geometry.
Computer-readable medium and system configured for differential equation-based tomography
A computer-readable medium storing instructions for executing the described tomographic imaging processes, and a tomographic imaging system including a data processing component configured to access scattering parameter data and generate reconstructed images by solving the electromagnetic inverse problem via differential equations and estimating permittivity values with the training data-based regression approach.
The independent claims collectively cover a novel tomographic imaging process and system that solve electromagnetic inverse problems using differential equations with defined boundary conditions, estimate object permittivity through regression of scattering parameters based on training data, and determine object boundaries via antenna measurement-derived relations, enabling accurate three-dimensional reconstructed images from scattering data.
Stated Advantages
Enables accurately solving electromagnetic inverse problems using partial differential equations, overcoming the limitations of integral-equation-based methods.
Allows three-dimensional tomographic image reconstruction without requiring approximations such as point-source antennas, homogeneity along one axis, or the use of matching background media.
Reduces image reconstruction time significantly compared to prior art, enabling rapid biomedical imaging suitable for emergency scenarios like stroke or trauma where time is critical.
Eliminates the need for a lossy matching medium that attenuates useful signals, improving the system's dynamic range and detection capability.
Provides boundary determination methods that facilitate accurate image reconstruction by relating antenna measurements to object surface location.
Uses a regression-based approach with training data to estimate effective permittivity from complex scattering parameters, supporting accurate initial imaging and beamforming.
Documented Applications
Biomedical imaging, particularly tomographic imaging of biological objects such as a human head.
Rapid imaging to identify brain injuries such as hemorrhagic stroke or bleeding regions within the brain.
Portable tomographic imaging systems for on-site medical emergency use, for example at road or sport accident scenes.
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