| 1. |
- Dobsicek Trefna, Hana, 1979, et al.
(författare)
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Evolution of an UWB antenna for hyperthermia array applicator
- 2012
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Ingår i: Proceedings of 6th European Conference on Antennas and Propagation, EuCAP 2012. Prague, 26-30 March 2012.. - 9781457709180 ; , s. 1046 - 1048
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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.
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| 2. |
- Fhager, Andreas, 1976, et al.
(författare)
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Progress in clinical diagnostics and treatment with electromagnetic fields
- 2011
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Ingår i: Proceedings of the 5th European Conference on Antennas and Propagation, EUCAP 2011. Rome, 11-15 April 2011. - 9788882020743 ; , s. 1936-1937
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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.
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| 3. |
- Dobsicek Trefna, Hana, 1979
(författare)
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Advances in Microwave Hyperthermia Treatment using Time Reversal
- 2010
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The last twenty years have seen many clinical studies showing the ability of hyperthermia to remarkably enhance response to radiation therapy and chemotherapy. The objective of hyperthermia treatment is to raise the temperature in tumors to therapeutic levels, for a sufficient period of time, in order to achieve cell death or render the cells more sensitive to ionizing radiation and/or chemotherapy. One of the challenges in hyperthermia is to adequately heat deep-seated tumors while preventing surrounding healthy tissue from undesired heating and damage.In this thesis, a new focusing technique, based on a time-reversal (TR) approach, for microwave hyperthermia is described and evaluated. First, the method was tested numerically using 2-D computer models of breast and neck. The obtained results were encouraging and suggest a multifrequency approach, in which the choice of frequency depends on the treated area size as well as on the tumor volume.Building on these results, a specific broadband antenna array was designed. In this design the applicator is immersed in a matching liquid and consists of between 12 and 16 identical triangular patch elements placed in a ring antenna arrangement. Next, we built a TR-hyperthermia amplifier system that operates in both continuous and pulsed wave regimes. The accuracy of the signal delivery as prescribed by the treatment planning tool is similar to clinical standards. However, at present, the output power allows only for experiments with phantoms or animals. The results show great promise and will be further investigated in clinical studies. Finally, the feasibility of microwave thermal imaging as a non-invasive approach for temperature monitoring during the treatment was investigated. The initial results of this approach, which is based on the variation of the dielectric properties with temperature, are encouraging. Work is in progress to evaluate the prospects of integrating microwave thermometry into our TR-hyperthermia system.
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| 4. |
- Dobsicek Trefna, Hana, 1979, et al.
(författare)
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Antenna Applicator for Microwave Hyperthermia Treatment of Pediatric Brain Cancer
- 2014
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Ingår i: 8th European Conference on Antennas and Propagation, EuCAP 2014, The Hague, The Netherlands 6-11 April 2014. - 9788890701849
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- A novel antenna applicator for microwave hyperthermia allowing treatment of deep brain tumors is proposed. The applicator consists of up to 16 antennas placed around the head in a helmet-like set-up and operates at a frequency range of 430-1000~MHz. The self-grounded bow-tie antennas are housed in a molded plastic enclosure with the shape of a truncated cone. The inner space of the enclosure is filled with distilled water. The antennas are attached to a perimetric water bolus with a thickness of 2 cm and aligned with the head shape. The focusing ability of the applicator was investigated on a homogeneous SAM model and on a model of a 13-year old patient containing a spherical tumor of 2 cm radius. Two different tumor positions were investigated: the right frontal lobe and the central brain. The obtained SAR distributions are favorable, although a relatively high level of energy is also absorbed on the surface of the body. This heating is however not expected to cause problems as it can be cooled by blood perfusion and water bolus. Our results show that focused microwave heating in the brain is feasible and warrants further verification on phantoms.
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| 5. |
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| 6. |
- Dobsicek Trefna, Hana, 1979, et al.
(författare)
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Design of a wideband multi-channel system for time reversal hyperthermia
- 2012
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Ingår i: International Journal of Hyperthermia. - : Informa UK Limited. - 0265-6736 .- 1464-5157. ; 28:2, s. 175-183
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Tidskriftsartikel (refereegranskat)abstract
- Purpose: To design and test a wideband multi-channel amplifier system for time reversal (TR) microwave hyperthermia, operating in the frequency range 300 MHz-1 GHz, enabling operation in both pulsed and continuous wave regimes. This is to experimentally verify that adaptation of the heating pattern with respect to tumour size can be realised by varying the operating frequency of the antennas and potentially by using Ultra-wideband (UWB) pulse sequences instead of pure harmonic signals. Materials and methods: The proposed system consists of 12 identical channels driven by a common reference signal. The power and phase settings are applied with resolutions of 0.1W and 0.1 degrees, respectively. Using a calibration procedure, the measured output characteristics of each channel are interpolated using polynomial functions, which are then implemented into a system software algorithm driving the system feedback loop. Results: The maximum output power capability of the system varies with frequency, between 90 and 135W with a relative power error of +/- 6%. A phase error in the order of +/- 4 degrees has been achieved within the entire frequency band. Conclusions: The developed amplifier system prototype is capable of accurate power and phase delivery, over the entire frequency band of the system. The output power of the present system allows for an experimental verification of a recently developed TR-method on phantoms or animals. The system is suitable for further development for head and neck tumours, breast or extremity applications.
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| 7. |
- Dobsicek Trefna, Hana, 1979, et al.
(författare)
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Evaluation of a patch antenna applicator for time reversal hyperthemia
- 2010
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Ingår i: International Journal of Hyperthermia. - : Informa UK Limited. - 0265-6736 .- 1464-5157. ; 26:2, s. 185-197
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Tidskriftsartikel (refereegranskat)abstract
- Purpose: To describe the design, analysis and evaluation of a new antenna array system for microwave hyperthermia. The proposed antenna array was evaluated by the focusing method based on the time-reversal principle. Materials and methods: Power absorption distributions in a cylindrical homogeneous and inhomogeneous phantom were calculated for the frequency range 500-900 MHz. Two set-ups with 12 and 16 antennas were analysed by comparing the changes in focusing areas enclosed by the 50%, 75% and 90% iso-SAR contours. For a more quantitative evaluation of the results the average power absorption ratio and remaining tissue maximum index were calculated. Results: The sharpest focusing area in the centre of the phantom, 151 mm
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| 8. |
- Dobsicek Trefna, Hana, 1979, et al.
(författare)
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Experimental verification of time-reversal microwave hyperthermia system
- 2011
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Ingår i: 30th URSI General Assembly and Scientific Symposium, URSIGASS 2011, Istanbul, 13-20 August 2011. - 9781424451173
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Konferensbidrag (refereegranskat)abstract
- In this contribution, we illustrate the performance of the developed UWB microwave hyperthermia system in combination with the treatment planning tool based on time-reversal algorithm. The experiment comparing the temperature distribution in muscle-equivalent phantom with the predicted SAR pattern was carried out at the ISM radio frequency 434 MHz. The obtained results have shown an excellent agreement between planned and measured data in terms of the correct focusing and iso-SAR countours.
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