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A numerical study of a radio frequency transceiver coil incorporating a capacitive metasurface is investigated for 1.5T magnetic resonance imaging of the cervical spinal cord. Full field simulations are carried out using the head of a human body model where the magnetic flux density (B1−) is compared to a standard transceiver coil. It is shown that an average improvement in B1− of 70% can be observed...
Ultrashort echo time imaging (UTE) is often the method of choice for measurement of short-lived T2 signals from biological tissues. The UTE acquisition is based on radial or spiral sampling schemes which, in general, are sensitive to small discrepancies between prescribed and actual trajectories. Such errors are usually observed as image quality degradation, visible as ghosting or intensity variation...
Thermal models for simulating heating and cooling of PIN diode and FET-based MRI coil blocking circuits are presented. The temperature dependent parameters in the two basic circuit elements as well as the related SPICE-compatible circuit models are discussed. Impedance versus temperature measurements for both PIN diode and MOSFET are presented that confirm the validity of model usage. A MRI coil blocking...
An optimized Metamaterial line resonator element for a Metamaterial imaging RF coil is developed for the ultrahigh field MRI systems. The coil element performance is compared to that of the transmission line (microstrip) [1] and the dipole [2,5] coil elements for the 10.5T MRI with a Larmor frequency of 447 MHz. Good penetration into the test phantom is observed for the Metamaterial element with negligible...
Monotonic scaling-down of CMOS integrated circuit (IC) technologies is rapidly approaching to its physical end, yet advances in ICs will continue. Instead of one-dimensional (1D) scaling dawn, one apparent solution is lateral integration of heterogeneous devices in 3-dimensional (3D) fashion, which opens great opportunities to make more complex Si-based microsystems for unlimited applications well...
Magnetic resonance imaging (MRI) plays a critical role in medicine today. Over the last few years, there has been an interest in techniques that use multiple coils on one side of the imaging system such as parallel excitation or parallel imaging to improve performance in high-field MRI. In this paper, we explore the use of multiple coils at both the transmit and receive sides for enhanced imaging...
Clinical studies have established that adjuvant mild hyperthermia significantly increases the efficacy of radio-and chemotherapy across many tumor sites. Radiofrequency hyperthermia treatment quality is usually monitored with invasive temperature sensors, which provides limited data sampling and causes infection risks. To mitigate these issues, magnetic resonance (MR) measurements can be exploited...
Sodium Magnetic Resonance Imaging (MRI) is an attractive imaging technique for early detection of osteoarthritis, as sodium concentrations correlate with proteoglycan content. However sodium yields much less signal in human tissues compared to hydrogen: it has a very rapid transverse signal decay (T2) and rapid longitudinal relaxation (T1), low gyromagnetic ratio and much smaller concentration than...
An MRI-guided radiation therapy linear accelerator was designed and tested for clinical implementation. The main investigation was related to the magnetic field coupling effects between the MR magnet and the therapy equipment, RF noise Isolation and overall system design for safe and streamlined clinical operation. The study involved numerical simulations of the magnetic field environment, which included...
In magnetic resonance imaging (MRI), the electrical performance of the RF coil is critical to achieve sufficient signal to noise ratio (SNR). In this work, the variation of performance of a plane and a flexible coil over a saline and a humanlike phantom is proposed. In order to evaluate the RF sensitivity of these flexible devices, we performed both an electrical characterization of the coil performances...
An anatomically realistic human head phantom was elaborated for different Larmor frequencies, which allows rapid quantification of B1+ of MRIs of different magnetic fields. The permittivity ε' and conductivity σ of sucrose/salt/agar aqueous solutions of varying concentration was determined; a solution with these components and having the adequate concentration to obtain the brain's dielectric properties...
Magnetic Resonance Imaging (MRI) is a widely used medical imaging technique. It employs a strong static magnetic field (1.5 to 10.5T for human imaging) to split the spin states of the 1H nuclei in the body, and RF excitation to induce transitions and coherence among them. Gradient fields are superimposed to modulate the 1H resonance frequency, which enables spatially distinguishable signals to be...
Spectral regrowth is a concern to the MRI system designer because of the potential for RF pulse distortion and subsequent excitation of nuclei outside of the region of interest. Previous work on spectral regrowth produced by series-connected PIN diodes has focused on their influence in communication systems but to the author's knowledge, no work to date has studied this spectral regrowth in MRI applications...
RF coils are essential part of Magnetic Resonance Imaging (MRI), which is a widely used imaging modality nowadays. Flexible surface RF coils are desired for potential higher signal to noise ratio (SNR) and ergonomic advantages. Electro-textiles are explored as potential candidate for MRI RF surface coils. A Flexible MRI RF coil for transmission or reception using electro-textiles is designed, fabricated...
We present approaches to enhancing magnetic field uniformity produced by RF probes in high-field Magnetic Resonance Imaging (MRI) scanners by introducing compensating non-uniformities in the probe designs. Unconventional designs of RF probes for operating at 600 MHz in 14 T MRI scanners are demonstrated, including a solenoid coil with non-uniform wrapping and dielectric separators, a system of microstrip...
A simultaneous and reconfigurable multi-level RF-interconnect (MRI) for global network-on-chip (NoC) communication is demonstrated. The proposed MRI interface consists of baseband (BB) and RF band transceivers. The BB transceiver uses multi-level signaling (MLS) to enhance communication bandwidth. The RF-band transceiver utilizes amplitude-shift keying (ASK) modulation to support simultaneous communication...
This paper presents a reflective capacitive impedance surface combined with a radio frequency loop coil to improve the radio frequency magnetic field for 1.5 Tesla magnetic resonance imaging applications. The proposed structure is based on a miniaturized surface unit cell using an inter digital capacitance approach. Full field simulations employing an inter digital frequency selective surface shows...
We review our recent work on the application of advanced electromagnetic structures for Magnetic Resonance Imaging. We discuss the use of metasurfaces and metamaterials resonators in order to locally enhance the sensitivity of radiofrequency coils in daily medical examinations. We will show in particular our recent experimental results about giant signal-to-noise ratio enhancement by arrays of nonmagnetic...
Receiver coil arrays are used in magnetic resonance imaging or spectroscopy systems to increase the system's signal-to-noise. However, the circulating currents in each coil, distorts the signal in the other coils of the array. To attenuate the circulating currents, each coil is terminated with a parallel resonance network and the signal is detected in the current-domain by a low input-impedance amplifier...
The advent of magnetic resonance imaging (MRI) and functional magnetic resonance imaging (fMRI) of the brain has changed forever conventional patient diagnosis and treatment in medicine. Instead of employing invasive procedures, now physicians can not just literally see internal body structures but also understand and map more clearly brain functions related to specific tasks, feelings, and behaviors...
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