Numerical and Workbench Design of 2.35 T Double-Tuned (¹H/²³Na) Nested RF Birdcage Coils Suitable for Animal Size MRI

Fantasia, M.; Galante, A.; Maggiorelli, Francesca; Retico, Alessandra; Fontana, Nunzia; Monorchio, Agostino; Alecci, Marcello

doi:10.1109/tmi.2020.2988599

Cited by 14 publications

(10 citation statements)

References 52 publications

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“…An auto-open region radiation boundary condition was chosen to surround the birdcage resonator. Although we are aware that this boundary condition might result in a slight overestimation of the simulated B 1 field due to RF shielding within the bore in MRI scanners [50], we believe this will not change the qualitative results presented here. During experiments (discussed later) the Pt and 3C-SiC samples (Figure 1b,c) were placed inside a tube and fixed in-place using a 3D printed polyacrylic acid (PLA) holder.…”

Section: Finite Element Methods Simulationsmentioning

confidence: 87%

Silicon Carbide and MRI: Towards Developing a MRI Safe Neural Interface

et al. 2021

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An essential method to investigate neuromodulation effects of an invasive neural interface (INI) is magnetic resonance imaging (MRI). Presently, MRI imaging of patients with neural implants is highly restricted in high field MRI (e.g., 3 T and higher) due to patient safety concerns. This results in lower resolution MRI images and, consequently, degrades the efficacy of MRI imaging for diagnostic purposes in these patients. Cubic silicon carbide (3C-SiC) is a biocompatible wide-band-gap semiconductor with a high thermal conductivity and magnetic susceptibility compatible with brain tissue. It also has modifiable electrical conductivity through doping level control. These properties can improve the MRI compliance of 3C-SiC INIs, specifically in high field MRI scanning. In this work, the MRI compliance of epitaxial SiC films grown on various Si wafers, used to implement a monolithic neural implant (all-SiC), was studied. Via finite element method (FEM) and Fourier-based simulations, the specific absorption rate (SAR), induced heating, and image artifacts caused by the portion of the implant within a brain tissue phantom located in a 7 T small animal MRI machine were estimated and measured. The specific goal was to compare implant materials; thus, the effect of leads outside the tissue was not considered. The results of the simulations were validated via phantom experiments in the same 7 T MRI system. The simulation and experimental results revealed that free-standing 3C-SiC films had little to no image artifacts compared to silicon and platinum reference materials inside the MRI at 7 T. In addition, FEM simulations predicted an ~30% SAR reduction for 3C-SiC compared to Pt. These initial simulations and experiments indicate an all-SiC INI may effectively reduce MRI induced heating and image artifacts in high field MRI. In order to evaluate the MRI safety of a closed-loop, fully functional all-SiC INI as per ISO/TS 10974:2018 standard, additional research and development is being conducted and will be reported at a later date.

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Section: Finite Element Methods Simulationsmentioning

confidence: 87%

Silicon Carbide and MRI: Towards Developing a MRI Safe Neural Interface

et al. 2021

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“…The birdcage is the workhorse volume RF coil in many MRI preclinical and clinical applications from the very low field (mT) up to ultra-high field (7 T) [24,25]. The implementation of double-tuned RF coils based on the birdcage design has been also reported [26][27][28][29].…”

Section: Fdtd Methodsmentioning

confidence: 99%

A Practical Guide to Estimating Coil Inductance for Magnetic Resonance Applications

et al. 2022

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Radiofrequency (RF) coils are employed to transmit and/or receive signals in Magnetic Resonance (MR) systems. The design of home-made, organ-specific RF coils with optimized homogeneity and/or Signal-to-Noise Ratio (SNR) can be a plus in many research projects. The first step requires accurate inductance calculation, this depending on the conductor’s geometry, to later define the tuning capacitor necessary to obtain the desired resonance frequency. To fulfil such a need it is very useful to perform a priori inductance estimation rather than relying on the time-consuming trial-and-error approach. This paper describes and compares two different procedures for coil inductance estimation to allow for a fast coil-prototyping process. The first method, based on calculations in the quasi-static approximation, permits an investigation on how the cross-sectional geometry of the RF coil conductors affects the total inductance and can be easily computed for a wide variety of coil geometries. The second approach uses a numerical full-wave method based on the Finite-Difference Time-Domain (FDTD) algorithm, and permits the simulation of RF coils with any complex geometry, including the case of multi-element phased array. Comparison with workbench measurements validates both the analytical and numerical results for RF coils operating within a wide field range (0.18–7 T).

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“…On the other hand, demand also lies in the acquisition of both the proton signal (anatomical information) and the X‐nuclei signal (e.g., for biochemical process analysis), with the same coil set to avoid subject movement during coil switching and to minimize the experimental time and complexity. For instance, a double‐tuned multichannel bilateral RF coil for 1 H/ 23 Na was built to provide sufficient SNR in less than 10 min in breast sodium imaging, while a double‐tuned nested birdcage coil was also reported to detect sodium signal over a large homogeneous volume 128,129 . Bent dipole antennas tuned to 1 H were integrated with a four‐channel 31 P loop coil array, providing 15% higher signal than that of a dual‐tuned birdcage 130 .…”

Section: Mn Mri/mrs Techniquesmentioning

confidence: 99%

MR‐Nucleomics: The study of pathological cellular processes with multinuclear magnetic resonance spectroscopy and imaging in vivo

Sun

Lin

et al. 2022

NMR in Biomedicine

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Clinical medicine has experienced a rapid development in recent decades, during which therapies targeting specific cellular signaling pathways, or specific cell surface receptors, have been increasingly adopted. While these developments in clinical medicine call for improved precision in diagnosis and treatment monitoring, modern medical imaging methods are restricted mainly to anatomical imaging, lagging behind the requirements of precision medicine. Although positron emission tomography and single photon emission computed tomography have been used clinically for studies of metabolism, their applications have been limited by the exposure risk to ionizing radiation, the subsequent limitation in repeated and longitudinal studies, and the incapability in assessing downstream metabolism. Magnetic resonance spectroscopy (MRS) or spectroscopic imaging (MRSI) are, in theory, capable of assessing molecular activities in vivo, although they are often limited by sensitivity. Here, we review some recent developments in MRS and MRSI of multiple nuclei that have potential as molecular imaging tools in the clinic.

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Numerical and Workbench Design of 2.35 T Double-Tuned (¹H/²³Na) Nested RF Birdcage Coils Suitable for Animal Size MRI

Cited by 14 publications

References 52 publications

Silicon Carbide and MRI: Towards Developing a MRI Safe Neural Interface

Silicon Carbide and MRI: Towards Developing a MRI Safe Neural Interface

A Practical Guide to Estimating Coil Inductance for Magnetic Resonance Applications

MR‐Nucleomics: The study of pathological cellular processes with multinuclear magnetic resonance spectroscopy and imaging in vivo

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