| 1. |
- Hosseinzadegan, Samar, 1987, et al.
(författare)
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Integrating the discrete dipole approximation forward solver with a microwave tomography algorithm
- 2018
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Ingår i: 2018 IEEE ANTENNAS AND PROPAGATION SOCIETY INTERNATIONAL SYMPOSIUM ON ANTENNAS AND PROPAGATION & USNC/URSI NATIONAL RADIO SCIENCE MEETING. - 1522-3965. - 9781538671023 - 9781538671023 ; , s. 2295-2296
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Konferensbidrag (refereegranskat)abstract
- The discrete dipole approximation (DDA) has been suggested as a viable alternative method for computing the forward solutions during the iterative reconstruction process used in microwave tomography. While efficient algorithms such as finite difference time domain and finite elements have been successfully used by multiple groups, the forward solution time remains the time-limiting step. The DDA has been shown to be accurate and efficient as a forward solver. However, the configuration of the imaging scenario can have a significant impact on its efficiency. We examine two possible forward solution set-ups and describe the benefits with respect to implementing the DDA.
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| 2. |
- Hosseinzadegan, Samar, 1987, et al.
(författare)
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On the electric field of microwave imaging systems using discrete dipole approximation
- 2018
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Ingår i: 2018 IEEE Conference on Antenna Measurements and Applications, CAMA 2018. - 9781538657959
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Konferensbidrag (refereegranskat)abstract
- The two dimensional electric field for our microwave imaging system consisting of 16 low profile monopole antennas is modelled via the discrete dipole approximation (DDA). We have used two dimensional electromagnetic waves in frequency domain in COMSOL Multiphysics to assess the level of reliability of the proposed two dimensional numerical solver, the 2-D DDA. Our observations show that the DDA is mainly dependent on the applied resolution on the imaging domain while physical properties in the media also contribute to the overall error.
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| 3. |
- Meaney, Paul M, 1960, et al.
(författare)
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A Transmission-Based Dielectric Property Probe for Clinical Applications
- 2018
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Ingår i: Sensors. - : MDPI AG. - 1424-8220. ; 18:10
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Tidskriftsartikel (refereegranskat)abstract
- We have developed a transmission-based, open-ended coaxial dielectric probe that can be used in clinical situations and overcomes many of the limitations related to the typical reflection-based dielectric probes. The approach utilizes the low profile, open-ended coaxial cables enabling clinicians to still probe relatively compact spaces. The sensing depth can be extended to as large as 1.5 to 2 cm compared with the more typical range of 0.3 mm for conventional probes and is dramatically less affected by measurement technique variability including poor sample contact and cable bending. As a precursor to an actual clinical implementation, we study the technique in a range of homogeneous liquids with substantially varying dielectric properties. The initial results demonstrate good agreement between the transmission-based probe and commercial, reflection-based probes and pave the way for more substantial clinical implementation.
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| 4. |
- Meaney, Paul M, 1960, et al.
(författare)
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Examination of the sensitivity matrix during the iterative reconstruction process for microwave tomography
- 2018
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Ingår i: 2018 IEEE Conference on Antenna Measurements and Applications, CAMA 2018.
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Konferensbidrag (refereegranskat)abstract
- We have reconstructed microwave tomographic images utilizing a Gauss-Newton scheme with a log transformation. While the recovered images are quite good, we have analyzed the behavior of the associated Jacobian, or sensitivity, matrix with respect to how it evolves during the reconstruction process. We found that in general the highest sensitivities are along the periphery of the imaging zone confirming the fact that most algorithms operate best for features nearest the outside. Interestingly, our log transformed algorithm appears to evolve during the reconstruction process to increase its internal sensitivity once the major exterior ones have been resolved. These results provide useful insight into a key driver of the reconstruction process and provide useful tools for assessing different system design criteria.
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| 5. |
- Meaney, Paul M, 1960, et al.
(författare)
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Visualization of the effects of multipath signals in complementary imaging and dielectric probing scenarios
- 2018
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Ingår i: 2018 IEEE Conference on Antenna Measurements and Applications, CAMA 2018. - 9781538657959
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Konferensbidrag (refereegranskat)abstract
- Distinguishing the effects of multipath signals from desired ones is often a challenging proposition. In this paper, we present two examples where multipath signals have impacted the desired signals. In each case, solutions were found to either further attenuate the unwanted signals to irrelevant levels or to understand their behavior as a means of developing ways to avoid such problems. These examples are reasonably representative of challenges encountered by all systems and are illustrative of the challenges they present.
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| 6. |
- Rydholm, Tomas, 1991, et al.
(författare)
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Comparing a time-domain and frequency-domain based algorithm in microwave tomography
- 2018
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Ingår i: IET Conference Publications. - : Institution of Engineering and Technology. ; 2018:CP741
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Konferensbidrag (refereegranskat)abstract
- A comparison of two different reconstruction algorithms developed for microwave tomographic imaging has been performed. One of the algorithm is an FDTD algorithm and the other one is an FEM-based one. Simulated S-parameters for a 16-antenna system are generated for a numerical phantom, which are then used to solve the inverse problem. It is shown that both algorithms could use the generated S-parameters to successfully reconstruct the studied phantoms.
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| 7. |
- Rydholm, Tomas, 1991, et al.
(författare)
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Effects of the Plastic of the Realistic GeePS-L2S-Breast Phantom
- 2018
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Ingår i: Diagnostics. - : MDPI AG. - 2075-4418. ; 8:3
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Tidskriftsartikel (refereegranskat)abstract
- A breast phantom developed at the Supelec Institute was interrogated to study its suitability for microwave tomography measurements. A microwave measurement system based on 16 monopole antennas and a vector network analyzer was used to study how the S-parameters are influenced by insertion of the phantom. The phantom is a 3D-printed structure consisting of plastic shells that can be filled with tissue mimicking liquids. The phantom was filled with different liquids and tested with the measurement system to determine whether the plastic has any effects on the recovered images or not. Measurements of the phantom when it is filled with the same liquid as the surrounding coupling medium are of particular interest. In this case, the phantom plastic has a substantial effects on the measurements which ultimately detracts from the desired images.
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