scholarly journals Three-Line Microstrip Array for Whole-Body MRI System at 7 T

2020 ◽  
Vol 11 (1) ◽  
pp. 73
Author(s):  
Daniel Hernandez
Keyword(s):  
Magnetic Resonance ◽  
Patch Antenna ◽  
Triple Line ◽  
Human Model ◽  
Whole Body ◽  
Ongoing Research ◽  
Rf Transmitters ◽  
Coupled Lines ◽  
Microstrip Array ◽  
B1 Field

This paper proposes the use of a triple-line microstrip array for transmitting a magnetic field (|B1+|) into the whole body for magnetic resonance applications at ultra-high field strength, such as 7 T. We explored some technologies that can potentially be applied for whole-body 7 T magnetic resonance imaging, as there is ongoing research on this topic. The triple-line microstrip transmission line (t-MTL) array consists of 32 channels. Each channel has a t-MTL, comprising a main conductor line and two adjacent coupled lines. The adjacent lines are not connected directly to the source. This configuration resulted in increased intensity and a centered |B1+|-field. We compared the proposed structure and some reference radiofrequency (RF) transmitters, such as a patch antenna, using a magnet bore as a waveguide and a whole-body birdcage coil. We evaluated the performance of the t-MTL using cylindrical phantoms. We computed the |B1+|-field from each RF transmitter inside a 3D human model containing more than 200 tissues. We compared their uniformity and field intensity and proposed a t-MTL array that yielded better performance. The proposed design also showed a lower specific absorption rate compared with a patch antenna.

scholarly journals Design of a Dual-Purpose Patch Antenna for Magnetic Resonance Imaging and Induced RF Heating for Small Animal Hyperthermia

2021 ◽  
Vol 11 (16) ◽  
pp. 7290
Author(s):  
Donghyuk Kim ◽  
Daniel Hernandez ◽  
Kyoung-Nam Kim
Keyword(s):  
Magnetic Resonance Imaging ◽  
Magnetic Resonance ◽  
Patch Antenna ◽  
Larmor Frequency ◽  
Magnetic Flux Density ◽  
Cancer Tissue ◽  
Patch Antennas ◽  
Rf Heating ◽  
Resonance Imaging ◽  
B1 Field

The popularity of patch antennas in magnetic resonance imaging (MRI) has reduced because of the large size required for patch antennae to resonate. Since the size of the patch antenna is associated with the wavelength and the wavelengths that are used in MRI are substantially large, large antennas are used. Methods of reducing patch antenna sizes have been proposed; however, these methods reduce the penetration depth and uniformity. In this study, we reduced the area of the patch antenna by 30% by folding the ground and patch planes in a zigzag pattern. The patch antenna produced two main resonant modes. The first mode produced a uniform magnetic field that was used for MRI. The second mode produced a strong and focused electric (|E|)-field, which was used for radiofrequency (RF) heating. Furthermore, we explored the use of a combination of two patch antennas aligned along the z-axis to provide a circular uniform magnetic flux density (|B1|) field at 300 MHz, which corresponds to the Larmor frequency in the 7T MRI system. In addition, the patch antenna configuration will be used for RF heating hyperthermia operating at 1.06 GHz. The target object was a small rat with insertion of colon cancer. Using the proposed configuration, we achieved |B1|-field uniformity with a standard deviation of 3% and a temperature increment of 1 °C in the mimic cancer tissue.

scholarly journals Design and Implementation of Split-Leg Type Elliptical Whole-Body Birdcage RF Coil at 1.5 T MRI

2021 ◽  
Vol 11 (16) ◽  
pp. 7448
Author(s):  
Suchit Kumar ◽  
Han-Jae Chung ◽  
You-Jin Jeong ◽  
Heung-Kyu Lee ◽  
Chang-Hyun Oh
Keyword(s):  
Human Subjects ◽  
Three Dimensional ◽  
System Optimization ◽  
Transmission Efficiency ◽  
Human Model ◽  
Whole Body ◽  
Rf Coil ◽  
Field Uniformity ◽  
B1 Field

The feasibility and the development of a four-port elliptical birdcage radio frequency (RF) coil for generating a homogenous RF magnetic (B1) field is presented for a space-constrained narrow-bore magnetic resonance imaging (MRI) system. Optimization was performed for the elliptical birdcage RF coil by adjusting the position and the structure of the legs to maximize the B1+-field uniformity. Electromagnetic (EM) simulations based on RF coil circuit co-simulations were performed on a cylindrical uniform phantom and a three-dimensional human model to evaluate the B1+-field uniformity, the transmission efficiency, and the specific absorption rate (SAR) deposition. An elliptical birdcage RF coil was constructed, and its performance was evaluated through network analysis measurements such as S-parameters and Q-factor. Quadrature transmit and receive MRI experiments were conducted using both phantom and in vivo human for validation. The EM simulation results indicate reasonable B1+-field uniformity and transmission efficiency for the proposed elliptical birdcage RF coil. The signal-to-noise ratio and the flip angle maps of the uniform phantom and the in vivo human MR images acquired using an elliptical birdcage (62 cm × 58 cm) were similar to those of a commercial circular birdcage (diameter, 58 cm), thereby indicating acceptable performance. In conclusion, the proposed split-type asymmetric elliptical birdcage RF coil is useful for whole-body MRI applications and can be used for imaging larger human subjects comfortably in a spacious imaging space.

Whole-body magnetic resonance imaging: a useful additional sequence in paediatric imaging

2004 ◽  
Vol 34 (6) ◽  
pp. 472-480 ◽  
Author(s):  
Eoghan E. Laffan ◽  
Rachael O’Connor ◽  
Stephanie P. Ryan ◽  
Veronica B. Donoghue
Keyword(s):  
Magnetic Resonance Imaging ◽  
Magnetic Resonance ◽  
Whole Body ◽  
Resonance Imaging ◽  
Body Magnetic Resonance Imaging ◽  
Paediatric Imaging ◽  
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