| 1. |
- Dobsicek Trefna, Hana, 1979, et al.
(författare)
-
Evolution of an UWB antenna for hyperthermia array applicator
- 2012
-
Ingår i: Proceedings of 6th European Conference on Antennas and Propagation, EuCAP 2012. Prague, 26-30 March 2012.. - 9781457709180 ; , s. 1046 - 1048
-
Konferensbidrag (refereegranskat)abstract
- Designs of three UWB antennas and their suitability to be used as a basis antenna element in the hyperthermia applicator for the treatment of tumors in head and neck region are considered. The antennas with reflection coefficient less than -10 dB at frequency range 350 MHz to 1 GHz are immersed in water bolus. The evaluation of the SAR distributions was carried out by comparing the different cross-sections of muscle equivalent phantom. Numerical simulations were performed in CST Microwave studio and verified experimentally via measurements of S-parameters and SAR distributions in phantoms.
|
|
| 2. |
- Fhager, Andreas, 1976, et al.
(författare)
-
Progress in clinical diagnostics and treatment with electromagnetic fields
- 2011
-
Ingår i: Proceedings of the 5th European Conference on Antennas and Propagation, EUCAP 2011. Rome, 11-15 April 2011. - 9788882020743 ; , s. 1936-1937
-
Konferensbidrag (refereegranskat)abstract
- There is a need for novel diagnostic and treatment systems to overcome the limitations with todays modalities. Microwave and THz based system has the potential to become both sensitive and specific in several applications. In this paper we discuss several applications that are currently being developed at the Chalmers University of Technology.
|
|
| 3. |
- Dahlbäck, Robin, 1985, et al.
(författare)
-
A 340 GHz CW non-linear imaging system
- 2010
-
Ingår i: Infrared Millimeter and Terahertz Waves (IRMMW-THz), 2010. - 9781424466559
-
Konferensbidrag (refereegranskat)abstract
- A CW sub-millimetre wave imaging system is presented. The system operates around 340GHz with a 6.5% relative bandwidth and uses a non-linear imaging algorithm.
|
|
| 4. |
- Dahlbäck, Robin, 1985, et al.
(författare)
-
A System for THz Imaging of Low-Contrast Targets Using the Born Approximation
- 2012
-
Ingår i: IEEE Transactions on Terahertz Science and Technology. - 2156-342X .- 2156-3446. ; 2:3, s. 361-370
-
Tidskriftsartikel (refereegranskat)abstract
- A THz imaging system, operating at 346 GHz and tailored for implementation of an imaging algorithm based on the Born approximation, is presented. The imaging algorithm provides focusing by compensating for the antenna footprint. This allows for using a more simple antenna system without optical focusing. Several aspects of implementing an imaging algorithm based on the Born approximation in THz imaging are discussed and key system properties are highlighted. The performance of the imaging algorithm is verified by imaging two simple dielectric targets. The results indicate that this approach provides a qualitative indication of the distribution of contrast in the samples complex permittivity and is a potential complement to existing imaging techniques.
|
|
| 5. |
- Fhager, Andreas, 1976, et al.
(författare)
-
Modeling and reconstruction in a 3D microwave imaging system
- 2011
-
Ingår i: 30th URSI General Assembly and Scientific Symposium, URSIGASS 2011, Istanbul, 13-20 August 2011. - 9781424451173
-
Konferensbidrag (refereegranskat)abstract
- In this paper we discuss the design and modeling of a 3D system for microwave imaging. The antenna system consists of 32 monopoles in a cylindrical configuration. A FDTD model of the system is used in the imaging reconstruction algorithm. Here we show a comparison of the data generated from the numerical FDTD model with measured data, as well as imaging of a simple target using this system. The agreement in the model is good and the imaging of a test object is successful.
|
|
| 6. |
- Jensen, P. D., et al.
(författare)
-
Nonlinear 3-D microwave imaging for breast-cancer screening: Log, phase and log-phase formulation
- 2011
-
Ingår i: LAPC 2011 - 2011 Loughborough Antennas and Propagation Conference. - 9781457710155
-
Konferensbidrag (refereegranskat)abstract
- The imaging algorithm used in the 3-D microwave imaging system for breast cancer screening, currently being developed at the Technical University of Denmark, is based on an iterative Newton-type algorithm. In this algorithm, the distribution of the electromagnetic constitutive parameters is updated in each iteration based on a comparison between the measured signals and the signals computed by a forward solver for the current parameter distribution. A key feature of the algorithm is the use of the log-phase formulation in which the measured complex signals are represented by the logarithm of their amplitudes and their unwrapped phases. In this paper, simplifications of the log-phase formulation are proposed, namely the log formulation, in which only the logarithm of the amplitudes are used, and the phase formulation, in which only the unwrapped phases are used. These formulations allow for the use of simpler tomographic systems in which only the amplitudes or the phases of the signals are measured. The performance of the algorithms using the two proposed formulations is investigated by reconstructing images of data collected with the above-mentioned imaging system, and the resulting images are compared with those obtained using the log-phase formulation.
|
|
| 7. |
- Jensen, P. D., et al.
(författare)
-
Parameter Scaling in Non-Linear Microwave Tomography
- 2012
-
Ingår i: 2012 Loughborough Antennas & Propagation Conference, Loughborough, United Kingdom, 12-13 November 2012. - 9781467322201
-
Konferensbidrag (refereegranskat)abstract
- Non-linear microwave tomographic imaging of the breast is a challenging computational problem. The breast is heterogeneous and contains several high-contrast and lossy regions, resulting in large differences in the measured signal levels. This implies that special care must be taken when the imaging problem is formulated. Under such conditions, microwave imaging systems will most often be considerably more sensitive to changes in the electromagnetic properties in certain regions of the breast. The result is that the parameters might not be reconstructed correctly in the less sensitive regions. In this paper, a method for obtaining a more uniform sensitivity throughout the breast is investigated. The method for obtaining uniform sensitivity throughout the imaging domain is a scaling of the parameters to be reconstructed. This scaling, based on the norms of the columns of the Jacobian, is also introduced as a measure of the sensitivity. The scaling of the parameters is shown to improve performance of the microwave imaging system when applied to reconstruction of images from 2-D simulated data and measurement data.
|
|
| 8. |
- Jensen, P. D., et al.
(författare)
-
Utilization of multiple frequencies in 3D nonlinear microwave imaging
- 2012
-
Ingår i: Proceedings of 6th European Conference on Antennas and Propagation, EuCAP 2012. Prague, 26-30 March 2012. - 9781457709180 ; , s. 1776-1779
-
Konferensbidrag (refereegranskat)abstract
- The use of multiple frequencies in a nonlinear microwave algorithm is considered. Using multiple frequencies allows for obtaining the improved resolution available at the higher frequencies while retaining the regularizing effects of the lower frequencies. However, a number of different challenges arise when using data from multiple frequencies for imaging of biological targets. In this paper, the performance of a multi-frequency algorithm, in which measurement data from several different frequencies are used at once, is compared with a stepped-frequency algorithm, in which images reconstructed at lower frequencies are used as starting guesses for reconstructions at higher frequencies. The performance is illustrated using simulated 2-D data and data obtained with the 3-D DTU microwave imaging system.
|
|
| 9. |
- Rubaek, Tonny, 1979, et al.
(författare)
-
A Contrast Source Inversion Algorithm Formulated Using the Log-Phase Formulation
- 2011
-
Ingår i: International Journal of Antennas and Propagation. - : Hindawi Limited. - 1687-5869 .- 1687-5877. ; 2011
-
Tidskriftsartikel (refereegranskat)abstract
- The contrast source inversion (CSI) algorithm was introduced for microwave imaging in 1997 and has since proven to be one of the most successful algorithms for nonlinear microwave tomography. In the CSI algorithm, the nonlinear integral equation, which must be solved to extract the constitutive electromagnetic parameters of the object under test from the microwave measurements, is represented by two linear equations, known as the data and the object equations. In this paper, the data equation in the CSI algorithm is reformulated using the so-called log-phase formulation. In this formulation, the measured data is represented by the change in the logarithm of the amplitude and the change in the unwrapped phase. This formulation has previously been applied for nonlinear tomography within the framework of a Gauss-Newton based algorithm for detection of breast cancer. Here, significant improvements have been observed compared to the more commonly used real-imaginary formulation. The modified CSI algorithm is tested on both simulated data and on a measurement of a breast. It is shown that for imaging setups with large differences in the measured signals, the new formulation of the data equation significantly improves the performance of the CSI algorithm.
|
|
| 10. |
- Rubaek, Tonny, 1979, et al.
(författare)
-
A single-channel THz imaging system for biomedical applications
- 2011
-
Ingår i: 30th URSI General Assembly and Scientific Symposium, URSIGASS 2011, Istanbul, 13-20 August 2011. - 9781424451173
-
Konferensbidrag (refereegranskat)abstract
- Due to technological advances, imaging in the THz-range of the electromagnetic spectrum is currently emerging as an interesting tool for security, safety, and biomedical applications. In this paper, a THz imaging system designed for biomedical analysis is described. The system consists of a pair of antennas operating in transmission mode at 335 GHz. The antennas can be moved independently of each other and a tomographic imaging algorithm is used to reconstruct the images.
|
|
