Wideband Self-Grounded Bow-Tie Antenna for Thermal MR
Journal article, 2020
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).
self-grounded bow-tie
thermal magnetic resonance
broadband antenna
ultrahigh field MR
thermal intervention
magnetic resonance
radiofrequency antenna
Author
Thomas Wilhelm Eigentler
Technische Universität Berlin
Helmholtz
Lukas Winter
Helmholtz
Physikalisch-Technische Bundesanstalt (PTB)
Haopeng Han
Helmholtz
Humboldt University of Berlin
Eva Oberacker
Helmholtz
Andre Kuehne
MRI TOOLS GmbH
Helmar Waiczies
MRI TOOLS GmbH
Sebastian Schmitter
Physikalisch-Technische Bundesanstalt (PTB)
Laura Boehmert
Berlin Institute of Health
Freie Universität Berlin
Helmholtz
Charité University Medicine Berlin
Humboldt University of Berlin
Christian Prinz
Charité University Medicine Berlin
Berlin Institute of Health
Humboldt University of Berlin
Helmholtz
Freie Universität Berlin
Hana Dobsicek Trefna
Chalmers, Electrical Engineering, Signal Processing and Biomedical Engineering
Thoralf Niendorf
Helmholtz
ECRC
MRI TOOLS GmbH
NMR in Biomedicine
0952-3480 (ISSN) 1099-1492 (eISSN)
Vol. 33 5 e4274Subject Categories
Energy Engineering
Building Technologies
Other Electrical Engineering, Electronic Engineering, Information Engineering
DOI
10.1002/nbm.4274
PubMed
32078208