Compact self-grounded Bow-Tie antenna design for an UWB phased-array hyperthermia applicator

Takook, Pegah; Persson, Mikael; Gellermann, Johanna; Trefná, Hana Dobšíček

doi:10.1080/02656736.2016.1271911

Cited by 45 publications

(36 citation statements)

References 27 publications

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“…Hence, we expect that the optimum optimization and evaluation metric is dependent on the focusing ability of an applicator. Such dependence would make our analysis very important for new conformal applicators that are under development [38][39][40][41]. Application of these results to other anatomical sites and applicators are matter of ongoing research.…”

Section: Resultsmentioning

confidence: 99%

Predictive value of SAR based quality indicators for head and neck hyperthermia treatment quality

Bellizzi

Drizdal

Rhoon

et al. 2019

International Journal of Hyperthermia

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Purpose: Hyperthermia treatment quality determines treatment effectiveness as shown by the clinically derived thermal-dose effect relations. SAR based optimization factors are used as possible surrogate for temperature, since they are not affected by thermal tissue properties uncertainty and variations. Previously, target coverage (TC) at the 25% and 50% iso-SAR level was shown predictive for treatment outcome in superficial hyperthermia and the target-to-hot-spot-quotient (THQ) was shown to highly correlate with predictive temperature in deep pelvic hyperthermia. Here, we investigate the correlation with temperature for THQ and TC using an 'intermediate' scenario: semi-deep hyperthermia in the head & neck region using the HYPERcollar3D. Methods: Fifteen patient-specific models and two different planning approaches were used, including random perturbations to circumvent optimization bias. The predicted SAR indicators were compared to predicted target temperature distribution indicators T50 and T90, i.e., the median and 90th percentile temperature respectively. Results: The intra-patient analysis identified THQ, TC25 and TC50 as good temperature surrogates: with a mean correlation coefficient R 2 T50 ¼ 0.72 and R 2 T90 ¼0.66. The inter-patient analysis identified the highest correlation with TC25 (R 2 T50 ¼ 0.76, R 2 T90 ¼0.54) and TC50 (R 2 T50 ¼ 0.74, R 2 T90 ¼ 0.56). Conclusion: Our investigation confirmed the validity of our current strategy for deep hyperthermia in the head & neck based on a combination of THQ and TC25. TC50 was identified as the best surrogate since it enables optimization and patient inclusion decision making using one single parameter. ARTICLE HISTORY

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Section: Resultsmentioning

confidence: 99%

Predictive value of SAR based quality indicators for head and neck hyperthermia treatment quality

Bellizzi

Drizdal

Rhoon

et al. 2019

International Journal of Hyperthermia

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“…Antenna count and positioning also influence the focal point quality . Increasing the number of antennas enables a lower surface RF energy deposition, while the focal point quality can be improved by longitudinal steering using multiple rings of antenna along the z‐dimension . A variable frequency increases the degrees of freedom (amplitude, phase and frequency) to modulate the focal point quality .…”

Section: Introductionmentioning

confidence: 99%

“…Increasing the number of antennas enables a lower surface RF energy deposition, while the focal point quality can be improved by longitudinal steering using multiple rings of antenna along the z‐dimension . A variable frequency increases the degrees of freedom (amplitude, phase and frequency) to modulate the focal point quality . Reports on this subject suggest an ideal intervention frequency or a mix of intervention frequencies for a particular target and target location .…”

Section: Introductionmentioning

confidence: 99%

“…A variable frequency increases the degrees of freedom (amplitude, phase and frequency) to modulate the focal point quality . Reports on this subject suggest an ideal intervention frequency or a mix of intervention frequencies for a particular target and target location . A compact wideband antenna setup based on a self‐grounded bow‐tie (SGBT) antenna is a potential answer to the need for multiple rings and a high channel count setup to enable broadband thermal intervention .…”

Section: Introductionmentioning

confidence: 99%

“…Reports on this subject suggest an ideal intervention frequency or a mix of intervention frequencies for a particular target and target location . A compact wideband antenna setup based on a self‐grounded bow‐tie (SGBT) antenna is a potential answer to the need for multiple rings and a high channel count setup to enable broadband thermal intervention . While several previous reports on RF antenna systems have addressed these multiple issues individually, our objective with this new design was to achieve a comprehensive solution.…”

Section: Introductionmentioning

confidence: 99%

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Wideband Self‐Grounded Bow‐Tie Antenna for Thermal MR

et al. 2020

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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 ( 1 H) MRI, fluorine ( 19 F) MRI, MR thermometry and broadband thermal intervention integrated in a wholebody 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 1 H and 19 F 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 1 H and 19 F MRI was demonstrated for the thigh and forearm of a healthy volunteer. The SGBT RF antenna building block facilitated 19 F and 1 H 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 μT/√kW was achieved at a depth of 50 mm. Temperature simulations and heating experiments in a phantom demonstrated a temperature increase ΔT >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

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