An fem approach for the characterization of the RF field homogeneity at high field

ABSTRACT:A simple 2-D full wave model for the birdcage coil is described that includes the effects of shields, lossy layered media, and finite leg widths. This model has been implemented in Matlab, which provides a simple user interface. Using this model, various coil parameters such as signal-to-noise ratio (SNR), magnetic field homogeneity, magnetic field magnitude, etc. can be computed quickly. The efficiency of this model allows optimization of the coil geometry for particular applications. A method for finding the optimal coil radius in terms of SNR and homogeneity, given shield and sample radii, is presented.

Section: Introductionmentioning

confidence: 99%

2‐D full wave solution for the analysis and design of birdcage coils

Spence

Wright

2003

“…To solve the system of coupled differential equations in [11], it first has to be uncoupled through the transformation [12] where the T matrices of eigenvectors satisfy …”

Section: Transformationmentioning

confidence: 99%

“…The finite element method (FEM) in the frequency domain is another numerical modeling approach that successfully has been applied to coil simulations (10,11). FEM discretizes the 3-D space into a collection of discrete elements of different sizes and interpolates the fields inside each element through so-called shape functions.…”

Section: Introductionmentioning

confidence: 99%

Analysis of high‐field RF coils using the method of lines

Bodganov

Ludwig

2003

ABSTRACT:The method of lines is described as a novel and powerful way to analyze radio frequency (RF) coils for high-field magnetic resonance imaging. Originally developed for optical and microwave circuits, this method enables a full-wave solution to Maxwell's field equations without the computational burden of pure finite element or finite difference methods. Because only two of the three geometric dimensions are discretized, while seeking an analytic solution in the remaining space dimension, an efficient solution can be obtained at reasonable geometric restrictions. After outlining the theoretical formulation and the computer implementation of this technique, we will apply it to the modeling of microstrip RF transverse electromagnetic resonator coils at 200 and 400 MHz as well as a high-pass shielded birdcage resonator and a single-loop surface coil. With single-frequency solutions obtainable within 5-10 s on a personal computer, the approach proves highly suitable as a design tool and for rapid prototyping.

“…MRI systems that employ 14 T to 20 T static magnetic fields (B 0 ) are expected to significantly advance animal and plant imaging. However, increased resonance frequencies for protons (600‐850 MHz) and, therefore, reduced wavelengths at these high fields have big implications on the performance of conventional radio‐frequency (RF) probes used to provide the alternating magnetic field (B1) . In particular, problems with phase shifts cause drastic deterioration of the magnetic field homogeneity of RF probes.…”

Section: Introductionmentioning

confidence: 99%

Approaches to designing micro‐solenoidal RF probes for 14 T MRI studies of millimeter‐range sized objects

Seifi

Semouchkina

Lanagan

et al. 2016

Full‐wave electromagnetic simulations have been employed to analyze the design approaches that allow for solving the problems preventing inductive performance of micro‐solenoidal RF probes and formation of strong and homogeneous magnetic fields inside probes at the studies of millimeter‐range sized objects in 14 T MRI scanners. In particular, the effects of non‐uniform coil wrapping on field homogeneity inside extended coils and of partitioning the coils by dielectric separators on coil self‐resonances have been investigated. The possibility to utilize tunable C‐C matching circuits with the coils and to mitigate the effects of sample insertion on the probe resonance frequency has been demonstrated. Challenges of coil fabrication have been also addressed.