| 1. |
- Carrapiço-Seabra, Carolina, et al.
(författare)
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Application of the ESHO-QA guidelines for determining the performance of the LCA superficial hyperthermia heating system
- 2023
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Ingår i: International Journal of Hyperthermia. - 0265-6736 .- 1464-5157. ; 40:1
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Tidskriftsartikel (refereegranskat)abstract
- Purpose: This study aimed to assess the quality of the lucite cone applicator (LCA), the standard applicator for superficial hyperthermia at the Erasmus MC Cancer Institute, using the most recent quality assurance guidelines, thus verifying their feasibility. Materials and methods: The assessment was conducted on each of the six LCAs available for clinical treatments. The temperature distribution was evaluated using an infrared camera across different layers of a fat-muscle mimicking phantom. The maximum temperature increase, thermal effective penetration depth (TEPD), and thermal effective field size (TEFS) were used as quality metrics. The experimental results were validated through comparison with simulated results, using a canonical phantom model and a realistic phantom model segmented from CT imaging. Results: A maximum temperature increase above 6 °C at 2 cm depth in the fat-muscle phantom for all the experiments was found. A mean negative difference between simulated and experimental data was of 1.3 °C when using the canonical phantom model. This value decreased to a mean negative difference of 0.4 °C when using the realistic model. Simulated and measured TEPD showed good agreement for both in silico scenarios, while discrepancies were present for TEFS. Conclusions: The LCAs passed all QA guidelines requirements for superficial hyperthermia delivery when used singularly or in an array configuration. A further characterization of parameters such as antenna efficiency and heat transfer coefficients would be beneficial for translating experimental results to simulated values. Implementing the QA guidelines was time-consuming and demanding, requiring careful preparation and correct setup of antenna elements.
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| 2. |
- de Lazzari, Mattia, 1996, et al.
(författare)
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Design and manufacture procedures of phantoms for hyperthermia QA guidelines
- 2023
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Ingår i: 17th European Conference on Antennas and Propagation, EuCAP 2023.
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Konferensbidrag (refereegranskat)abstract
- Clinical outcome of hyperthermia therapy (HT) is strongly correlated with the thermal dose delivered into the tumor. Achieving of prescribed temperature distribution within the target area should therefore the primary objective of any HT treatment. The Quality Assurance (QA) guidelines developed in past decennium by ESHO-TC establish the physical characterization and prescribe the safeguards to ensure that the clinically used equipment is capable of achieving adequate temperatures. The direct implementation of these guidelines is however limited by the lack of suitable phantom materials. To address this issue, we propose (i) a novel material to mimic fat tissue and (ii) a standardized phantom verification of phased array applicators for deep HT in Head and Neck (H&N) and extremities. In particular, (i) a fat-phantom composed of an ethylcellulose based oleogel exhibit equivalent dielectric and thermal properties with the required mechanical stability even at elevated temperatures, while (ii) the standardized phantom provides the means to capture the thermal profiles to evaluate the performance indicators in reproducible manner. Both phantoms thus bears a great potential for their extensive use in QA procedures.
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| 3. |
- de Lazzari, Mattia, 1996, et al.
(författare)
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Ethylcellulose-stabilized fat-tissue phantom for quality assurance in clinical hyperthermia
- 2023
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Ingår i: International Journal of Hyperthermia. - 0265-6736 .- 1464-5157. ; 40:1
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Tidskriftsartikel (refereegranskat)abstract
- Background: Phantoms accurately mimicking the electromagnetic and thermal properties of human tissues are essential for the development, characterization, and quality assurance (QA) of clinically used equipment for Hyperthermia Treatment (HT). Currently, a viable recipe for a fat equivalent phantom is not available, mainly due to challenges in the fabrication process and fast deterioration. Materials and methods: We propose to employ a glycerol-in-oil emulsion stabilized with ethylcellulose to develop a fat-mimicking material. The dielectric, rheological, and thermal properties of the phantom have been assessed by state-of-the-art measurement techniques. The full-size phantom was then verified in compliance with QA guidelines for superficial HT, both numerically and experimentally, considering the properties variability. Results: Dielectric and thermal properties were proven equivalent to fat tissue, with an acceptable variability, in the 8 MHz to 1 GHz range. The rheology measurements highlighted enhanced mechanical stability over a large temperature range. Both numerical and experimental evaluations proved the suitability of the phantom for QA procedures. The impact of the dielectric property variations on the temperature distribution has been numerically proven to be limited (around 5%), even if higher for capacitive devices (up to 20%). Conclusions: The proposed fat-mimicking phantom is a good candidate for hyperthermia technology assessment processes, adequately representing both dielectric and thermal properties of the human fat tissue while maintaining structural stability even at elevated temperatures. However, further experimental investigations on capacitive heating devices are necessary to better assess the impact of the low electrical conductivity values on the thermal distribution.
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| 4. |
- Dobsicek Trefna, Hana, 1979, et al.
(författare)
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Delivering Energy using Localized Hyperthermia Systems
- 2023
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Ingår i: The Application of Heat in Oncology: Principles and Practice. - 9781119799627 ; , s. 73-94
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Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- Clinical hyperthermia (HT) is the application of elevated temperatures to tumors to enhance the effectiveness of radiotherapy and chemotherapy. To realize an effective thermal dose, dedicated heating equipment is used for specific tumor locations (superficial or deep-seated) to induce localized heating via either internal or external devices. This chapter provides an overview of the existing heating techniques for clinical HT treatments. Furthermore, the selection of heating equipment is briefly discussed, as well as quality assurance procedures. To achieve elevated temperature, four heating techniques have been clinically used: electromagnetic and US heating, hyperthermic perfusion, and conductive heating. Accurate treatment planning and delivery are crucial to achieve HT treatment goals. The recent technological advances, when combined with the evolution of temperature-mediated drugs and immunotherapeutic approaches, are expected to lead to personalized HT approaches for cancer patients.
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| 5. |
- Dobsicek Trefna, Hana, 1979, et al.
(författare)
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Fat tissue equivalent phantoms for microwave applications by reinforcing gelatin with nanocellulose
- 2021
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Ingår i: Biomedical Physics and Engineering Express. - : IOP Publishing. - 2057-1976. ; 7:6
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Tidskriftsartikel (refereegranskat)abstract
- Tissue mimicking phantom materials with thermal and dielectric equivalence are vital for the development of microwave diagnostics and treatment. The current phantoms representing fat tissue are challenged by mechanical integrity at relevant temperatures coupled with complex production protocols. We have employed two types of nanocellulose (cellulose nanocrystals and oxidized cellulose nanocrystals) as reinforcement in gelatin stabilized emulsions for mimicking fat tissue. The nanocellulose-gelatin stabilized emulsions were evaluated for their dielectric properties, the moduli-temperature dependence using small deformation rheology, stress-strain behavior using large deformation, and their compliance to quality assurance guidelines for superficial hyperthermia. All emulsions had low permittivity and conductivity within the lower microwave frequency band, accompanied by fat equivalent thermal properties. Small deformation rheology showed reduced temperature dependence of the moduli upon addition of nanocellulose, independent of type. The cellulose nanocrystals gelatin reinforced emulsion complied with the quality assurance guidelines. Hence, we demonstrate that the addition of cellulose nanocrystals to gelatin stabilized emulsions has the potential to be used as fat phantoms for the development of microwave diagnostics and treatment.
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| 6. |
- Eigentler, Thomas Wilhelm, et al.
(författare)
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Wideband Self-Grounded Bow-Tie Antenna for Thermal MR
- 2020
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Ingår i: NMR in Biomedicine. - : Wiley. - 0952-3480 .- 1099-1492. ; 33:5
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Tidskriftsartikel (refereegranskat)abstract
- The objective of this study was the design, implementation, evaluation and application of a compact wideband self-grounded bow-tie (SGBT) radiofrequency (RF) antenna building block that supports anatomical proton (H-1) MRI, fluorine (F-19) MRI, MR thermometry and broadband thermal intervention integrated in a whole-body 7.0 T system. Design considerations and optimizations were conducted with numerical electromagnetic field (EMF) simulations to facilitate a broadband thermal intervention frequency of the RF antenna building block. RF transmission (B-1(+)) field efficiency and specific absorption rate (SAR) were obtained in a phantom, and the thigh of human voxel models (Ella, Duke) for H-1 and F-19 MRI at 7.0 T. B-1(+) efficiency simulations were validated with actual flip-angle imaging measurements. The feasibility of thermal intervention was examined by temperature simulations (f = 300, 400 and 500 MHz) in a phantom. The RF heating intervention (P-in = 100 W, t = 120 seconds) was validated experimentally using the proton resonance shift method and fiberoptic probes for temperature monitoring. The applicability of the SGBT RF antenna building block for in vivo H-1 and F-19 MRI was demonstrated for the thigh and forearm of a healthy volunteer. The SGBT RF antenna building block facilitated F-19 and H-1 MRI at 7.0 T as well as broadband thermal intervention (234-561 MHz). For the thigh of the human voxel models, a B-1(+) efficiency >= 11.8 mu T/root kW was achieved at a depth of 50 mm. Temperature simulations and heating experiments in a phantom demonstrated a temperature increase Delta T >7 K at a depth of 10 mm. The compact SGBT antenna building block provides technology for the design of integrated high-density RF applicators and for the study of the role of temperature in (patho-) physiological processes by adding a thermal intervention dimension to an MRI device (Thermal MR).
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| 7. |
- Fontes-Candia, Cynthia, et al.
(författare)
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Maximizing the oil content in polysaccharide-based emulsion gels for the development of tissue mimicking phantoms
- 2021
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Ingår i: Carbohydrate Polymers. - : Elsevier Ltd. - 0144-8617 .- 1879-1344. ; 256
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Tidskriftsartikel (refereegranskat)abstract
- Formulations based on agar and κ-carrageenan were investigated for the production of emulsion gels applicable as tissue mimicking phantoms. The effects of the polysaccharide matrix, the oil content and the presence of surfactants on the micro-/nanostructure, rheology, and mechanical and dielectric properties were investigated. Results showed a high capacity of the agar to stabilize oil droplets, producing gels with smaller (10−21 μm) and more uniform oil droplets. The addition of surfactants allowed increasing the oil content and reduced the gel strength and stiffness down to 57 % and 34 %, respectively. The permittivity and conductivity of the gels were reduced by increasing the oil content, especially in the agar gels (18.8 and 0.05 S/m, respectively), producing materials with dielectric properties similar to those of low-water content tissues. These results evidence the suitability of these polysaccharides to design a variety of tissue mimicking phantoms with a broad range of mechanical and dielectric properties.
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| 8. |
- Ghaderi Aram, Morteza, 1988, et al.
(författare)
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A phased array applicator based on open ridged-waveguide antenna for microwave hyperthermia
- 2021
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Ingår i: Microwave and Optical Technology Letters. - : Wiley. - 1098-2760 .- 0895-2477. ; 63:12, s. 3086-3091
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Tidskriftsartikel (refereegranskat)abstract
- Radiative hyperthermia is a clinically applied cancer treatment modality where antenna design is crucial to achieving therapeutic goals. Serving as the building block of a phased-array configuration, antennas are typically arranged in a cylindrical or elliptical array called applicator. This short communication proposes an elliptical phased array applicator based on a compact, UWB design from the category of double-ridged horn antennas customized for hyperthermia systems. The performance of the antenna, named open ridged-waveguide, has been experimentally assessed based on the quality metrics of the hyperthermic community. The proposed design achieves an ultra-wideband range of operation from 400 to 800 MHz with an aperture size of 3 by 4 cm. Moreover, thanks to the shielding provided by the metallic housing, the design proves good isolation better than -30 dB throughout the band. The power deposition capability of the proposed applicator followed by the thermal analysis is also investigated for a realistic head and neck patient model. The results indicate very good quality metrics achieved in the treatment planning of the patient.
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| 9. |
- Ghaderi Aram, Morteza, 1988, et al.
(författare)
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An ultra-wideband compact design for hyperthermia: Open ridged-waveguide antenna
- 2022
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Ingår i: IET Microwaves, Antennas and Propagation. - : Institution of Engineering and Technology (IET). - 1751-8725 .- 1751-8733. ; 16:2-3, s. 137-152
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Tidskriftsartikel (refereegranskat)abstract
- Antennas are the building block of radiative hyperthermia (HT) applicators. This study proposes a compact UWB antenna specifically tailored to meet the requirements for deep HT array applicators. The proposed Open Ridged-Waveguide (ORWG) antenna, which is an adaptation of a double-ridged horn antenna, operates over the frequency band of 400-800 MHz. It was experimentally assessed as a single element. The quality metrics considered were reflection coefficient, penetration depth, effective field size (EFS), and mutual coupling. The design shows a 75.5% fractional bandwidth with a reflection coefficient measured to be below -10 dB from 367 up to 820 MHz. The EFS is greater than the physical dimensions of the 3-by-4 cm aperture. The mutual coupling between two adjacent elements in the array, measured in a flat phantom arrangement, is lower than -30 dB throughout the entire band. The antenna's performance was further tested in two deep HT scenarios in order to assess the mutual coupling and focussing abilities while in the array configuration. To this end, phased array applicators consisting of 10 and 16 ORWG antennas were simulated in CST, and the results are presented for a homogeneous cylindrical muscle phantom and a realistic patient model, respectively. The good agreement between the simulated and measured results suggests that the antenna can be successfully used for HT.
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| 10. |
- Ghaderi Aram, Morteza, 1988, et al.
(författare)
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Microwave thermometry with potential application in non-invasive monitoring of hyperthermia
- 2020
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Ingår i: Journal of Inverse and Ill-Posed Problems. - : Walter de Gruyter GmbH. - 0928-0219 .- 1569-3945. ; 28:5, s. 739-750
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Tidskriftsartikel (refereegranskat)abstract
- Integration of an adaptive finite element method (AFEM) with a conventional least squares method has been presented. As a 3D full-wave forward solver, CST Microwave Studio has been used to model and extract both electric field distribution in the region of interest (ROI) and S-parameters of a circular array consisting of 16 monopole antennas. The data has then been fed into a differential inversion scheme to get a qualitative indicator of how the temperature distribution evolves over a course of the cooling process of a heated object. Different regularization techniques within the Tikhonov framework are also discussed, and a balancing principle for optimal choice of the regularization parameter was used to improve the image reconstruction quality of every 2D slice of the final image. Targets are successfully imaged via proposed numerical methods. © 2020 Ghaderi Aram, Beilina and Dobsicek Trefna, published by De Gruyter.
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