| 1. |
- Takook, Pegah, 1982, et al.
(författare)
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Prediction of tumor heatability in microwave hyperthermia applicators
- 2018
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Ingår i: IET Conference Publications. - : Institution of Engineering and Technology. ; 2018:CP741
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Konferensbidrag (refereegranskat)abstract
- In this paper, the heating efficiency of two hyperthermia applicators has been evaluated for the treatment of tumors in the brain. The effect of a high number of antennas and lower frequencies were investigated by employing one applicator with many antennas and one applicator with antennas operational in a lower frequency range. An investigation method was first used to find out the most difficult and easy places for heating inside the head. Given the applicator, patient model, and tumor position, the method is assessing whether or not the applicators are able to heat the tumor efficiently.
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| 2. |
- Paulides, M. M., et al.
(författare)
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ESHO benchmarks for computational modeling and optimization in hyperthermia therapy
- 2021
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Ingår i: International Journal of Hyperthermia. - : Informa UK Limited. - 0265-6736 .- 1464-5157. ; 38:1, s. 1425-1442
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Tidskriftsartikel (refereegranskat)abstract
- Background: The success of cancer hyperthermia (HT) treatments is strongly dependent on the temperatures achieved in the tumor and healthy tissues as it correlates with treatment efficacy and safety, respectively. Hyperthermia treatment planning (HTP) simulations have become pivotal for treatment optimization due to the possibility for pretreatment planning, optimization and decision making, as well as real-time treatment guidance. Materials and methods: The same computational methods deployed in HTP are also used for in silico studies. These are of great relevance for the development of new HT devices and treatment approaches. To aid this work, 3 D patient models have been recently developed and made available for the HT community. Unfortunately, there is no consensus regarding tissue properties, simulation settings, and benchmark applicators, which significantly influence the clinical relevance of computational outcomes. Results and discussion: Herein, we propose a comprehensive set of applicator benchmarks, efficacy and safety optimization algorithms, simulation settings and clinical parameters, to establish benchmarks for method comparison and code verification, to provide guidance, and in view of the 2021 ESHO Grand Challenge (Details on the ESHO grand challenge on HTP will be provided at https://www.esho.info/). Conclusion: We aim to establish guidelines to promote standardization within the hyperthermia community such that novel approaches can quickly prove their benefit as quickly as possible in clinically relevant simulation scenarios. This paper is primarily focused on radiofrequency and microwave hyperthermia but, since 3 D simulation studies on heating with ultrasound are now a reality, guidance as well as a benchmark for ultrasound-based hyperthermia are also included.
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| 3. |
- Zanoli, Massimiliano, 1989, et al.
(författare)
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Iterative time-reversal for multi-frequency hyperthermia
- 2021
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Ingår i: Physics in Medicine and Biology. - : IOP Publishing. - 0031-9155 .- 1361-6560. ; 66:4
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Tidskriftsartikel (refereegranskat)abstract
- Time-reversal (TR) is a known wideband array beam-forming technique that has been suggested as a treatment planning alternative in deep microwave hyperthermia for cancer treatment. While the aim in classic TR is to focus the energy at a specific point within the target, no assumptions are made on secondary lobes that might arise in the healthy tissues. These secondary lobes, together with tissue heterogeneity, may result in hot-spots (HSs), which are known to limit the efficiency of the thermal dose delivery to the tumor. This paper proposes a novel wideband TR focusing method that iteratively shifts the focus away from HSs and towards cold-spots from an initial TR solution, a procedure that improves tumor coverage and reduces HSs. We verify this method on two different applicator topologies and several target volume configurations. The algorithm is deterministic and runs within seconds, enabling its use for real-time applications. At the same time, it yields results comparable to those obtained with global stochastic optimizers such as Particle Swarm.
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| 4. |
- Bakker, A., et al.
(författare)
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Analysis of clinical data to determine the minimum number of sensors required for adequate skin temperature monitoring of superficial hyperthermia treatments
- 2018
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Ingår i: International Journal of Hyperthermia. - : Informa UK Limited. - 0265-6736 .- 1464-5157. ; 34:7, s. 910-917
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Tidskriftsartikel (refereegranskat)abstract
- Purpose: Tumor response and treatment toxicity are related to minimum and maximum tissue temperatures during hyperthermia, respectively. Using a large set of clinical data, we analyzed the number of sensors required to adequately monitor skin temperature during superficial hyperthermia treatment of breast cancer patients. Methods: Hyperthermia treatments monitored with >60 stationary temperature sensors were selected from a database of patients with recurrent breast cancer treated with re-irradiation (23 × 2 Gy) and hyperthermia using single 434 MHz applicators (effective field size 351–396 cm2). Reduced temperature monitoring schemes involved randomly selected subsets of stationary skin sensors, and another subset simulating continuous thermal mapping of the skin. Temperature differences (ΔT) between subsets and complete sets of sensors were evaluated in terms of overall minimum (Tmin) and maximum (Tmax) temperature, as well as T90 and T10. Results: Eighty patients were included yielding a total of 400 hyperthermia sessions. Median ΔT was 50 sensors were used. Subsets of 50 sensors were used. Thermal profiles (8–21 probes) yielded a median ΔT < 0.01 °C for T90 and Tmax, with a 95%CI of −0.2 °C and 0.4 °C, respectively. The detection rate of Tmax≥43 °C is ≥85% while using >50 stationary sensors or thermal profiles. Conclusions: Adequate coverage of the skin temperature distribution during superficial hyperthermia treatment requires the use of >50 stationary sensors per 400 cm2applicator. Thermal mapping is a valid alternative.
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| 5. |
- 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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| 6. |
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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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Time-reversal focusing in microwave hyperthermia for deep-seated tumors
- 2010
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Ingår i: Physics in Medicine and Biology. - : IOP Publishing. - 0031-9155 .- 1361-6560. ; 55:8, s. 2167-2185
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Tidskriftsartikel (refereegranskat)abstract
- A fast beam-forming method for hyperthermia treatment of deep-seated tumors is described and verified. The approach is based on the time-reversal characteristics of Maxwell equations. The basic principle of the method is coupling of the electromagnetic modeling of the system with the actual application. In this modeling the wavefront of the source is propagated through a patient-specific model from a virtual antenna placed in the tumor of the model. The simulated radiated field is then captured using a computer model of the surrounding antenna system. The acquired amplitudes and phases are then used in the real antenna system. The effectiveness of this procedure is demonstrated by calculating the power absorption distribution using FDTD electromagnetic simulations of a realistic 2D breast model as well as a 2D neck model. Several design parameters, i.e. number of antennas, operating frequency and dimensions, have been evaluated by performance indicators. The promising results suggest that the development of this technique is pursued further.
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| 9. |
- Dobsicek Trefna, Hana, 1979, et al.
(författare)
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TR-Hyperthermia: a system prototype
- 2009
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Ingår i: Society for Thermal Medicine 2009 Annual Meeting.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)
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| 10. |
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