Multi-Frequency Microwave Imaging with Stable Coupling Fluid
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Solution Overview
Problem
Current microwave imaging systems face challenges in achieving practical, preclinical imaging due to issues with coupling fluids, antenna design for near-field applications, data acquisition, and the effectiveness of inverse algorithms in real-world scenarios, particularly concerning signal loss, stability, and noise handling.
Innovation Solution
A novel microwave imaging system incorporating a new water-in-oil emulsion as coupling fluid, a quad-band tapered patch antenna array, an efficient data acquisition system, and an enhanced variational Born iterative method with bounding constraints for 3D dielectric imaging, addressing signal loss and noise through calibrated data processing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If glycerin-water mixture is used as coupling fluid, then dielectric contrast is controlled, but signal loss increases excessively
Solution Approach 1:
The patent changes the chemical composition parameters of the coupling fluid by using a water-in-oil emulsion with specific ratios of water (30-70%), oil (20-50%), and emulsifier (1-10%). This parameter adjustment optimizes both dielectric contrast and signal loss characteristics, achieving a balance between the two competing requirements.
Solution Approach 2:
The patent employs a composite water-in-oil emulsion system combining multiple components (water, oil, emulsifier) to create a coupling fluid with superior properties. The composite structure allows the system to achieve both adequate dielectric contrast and reduced signal loss compared to simple glycerin-water mixtures.
2Reliability
If water-in-oil emulsion is used as coupling fluid, then dielectric contrast is controlled, but temporal and thermal stability deteriorates
Solution Approach 1:
The patent introduces an emulsifier as an intermediary substance that stabilizes the water-in-oil emulsion. The emulsifier prevents phase separation and maintains the integrity of the coupling fluid over time and under thermal conditions, thereby improving temporal and thermal stability while preserving dielectric contrast control.
Solution Approach 2:
The patent optimizes the concentration of emulsifier (1-10% of total composition) to achieve the desired stability. By adjusting this parameter, the system maintains both the functional dielectric contrast and the structural stability of the coupling fluid during extended imaging sessions.
3Measurement precision
If conventional antennas are designed for far-field operation, then far-field parameters are optimized, but near-field performance in coupling fluid deteriorates
Solution Approach 1:
The patent applies local quality by designing antennas with specific characteristics suited for near-field operation in coupling fluid. The antenna elements are configured with optimized geometries and positions that are tailored for the specific electromagnetic environment of the imaging chamber, rather than using generic far-field optimized designs.
Solution Approach 2:
The patent employs a multi-frequency antenna system that can dynamically operate at different frequencies (500 MHz, 1000 MHz, 1500 MHz, 2000 MHz) depending on the imaging requirements. This dynamic capability allows the system to adapt to different near-field imaging scenarios and optimize performance for various target depths and resolutions.
4Device complexity
If single-frequency MWI system is used, then system complexity is reduced, but imaging resolution and penetration depth capability deteriorates
Solution Approach 1:
The patent segments the imaging task across multiple frequencies, with each frequency contributing to different aspects of the image (resolution, penetration, contrast). This segmentation allows the system to achieve comprehensive imaging capabilities that would be impossible at a single frequency, while managing complexity through modular frequency-specific processing.
Solution Approach 2:
The patent creates a multi-functional imaging system where a single antenna array can operate at multiple frequencies (500 MHz, 1000 MHz, 1500 MHz, 2000 MHz), enabling the system to perform various imaging functions including deep penetration imaging, high-resolution surface imaging, and intermediate-depth imaging within a single unified platform.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The system achieves accurate 3D dielectric mapping with improved signal-to-noise ratio and stability, enabling effective detection and characterization of targets in complex scenarios, demonstrating potential for preclinical imaging applications.
Implementation Method 1
MWI systems emit EM waves that are excited by antennas operating at microwave bands. Subsequently, MWI systems have no risk of ionization compared to computed tomography (CT) and X-ray scans
Implementation Method 2
MWI evaluates targets through the scattered EM field that arises from the dielectric contrast between unknown targets and the background
Implementation Method 3
a quad-band tapered patch antenna array... configured to have a plurality of resonant frequencies... The plurality of antennas includes a first subset of antennas configured as receiver antennas and a second set of antennas configured as transmitter antennas
Implementation Method 4
a quad-band tapered patch antenna array... configured to have a plurality of resonant frequencies
Implementation Method 5
an enhanced variational Born iterative method with bounding constraints for 3D dielectric imaging... capable of reconstructing the 3D dielectric relaxation model using measured data acquired at multiple transmit frequencies
Implementation Method 6
The plurality of antennas is a quad-band tapered patch antenna array... The system undergoes a comprehensive calibration procedure and post processing algorithm, to acquire the coherent scattering parameters of each transmit-receive pairs
Data Source
AI summary
A microwave imaging (MWI) system prototype to reconstruct three-dimensional (3D) complex dielectric images of various dielectric phantom models is provided. The imaging cavity of this system is filled with a newly compounded emulsion that provides a long-term stable and a controllable range of background-to-target dielectric contrasts. The system utilizes a tapered patch antenna array that enables multi-frequency operation. The the enhanced variational Born iterative method with bounding constraints (BC-VBIM) is applied as the inverse solver. Multiple experiments with various phantoms are conducted to evaluate the system's performance and imaging capabilities. Phantom models being used in this work for system evaluation include single, double, and multiple spherical targets filled with various water-isopropyl alcohol mixtures and submerged either directly in the background emulsion or within another water-alcohol mixture that is submerged in the emulsion.