Multi-channel magnetic resonance spectroscopy graphical user interface (McMRSGUI).

This work introduces an open-sourced graphical user interface (GUI) software enabling the combination of multi-channel magnetic resonance spectroscopy data with different literature-based methods for the improvement of the quality and reliability of combined spectra. The multi-channel magnetic resonance spectroscopy graphical user interface (McMRSGUI) is a MATLAB-based spectroscopy processing GUI equipped to load multi-channel MRS data, pre-process, combine, and export combined data for evaluation with open-source quantification software (jMRUI). A literature-based, decision-tree process was incorporated into the combination type selection to serve as a guide to minimize spectral distortion in selecting between weighting methods.

Evaluation of Low-Loss Polymer Switches for Multinuclear MRI/S.

Implementation of multinuclear MRI/S as a diagnostic tool in clinical settings faces many challenges. One of those challenges is the development of highly sensitive multinuclear RF coils. Current multi-tuning techniques incorporate lossy components that impact the highest achievable SNR for at least one of the coil frequencies.

Technical note: The design and validation of a multi-modality lung phantom.

Background: Clinically relevant models that enable certain tasks such as calibration of medical imaging devices or techniques, device validation, training healthcare professionals, and more are vital to research throughout the medical field and are referred to as phantoms. Phantoms range in complexity from a vile of water to complex designs that emulate in vivo properties.

Purpose: Specific phantoms that model the lungs have focused on replication of tissue properties but lack replication of the anatomy.

Assessing the Feasibility of Dynamic P Spectroscopy for Metabolic Studies With a 1.0T Extremity Scanner.

Objective: The feasibility of conducting in vivo non-localized P Magnetic Resonance Spectroscopy (MRS) with a 1.0T extremity scanner and the potential to increase accessibility of this important diagnostic tool for low cost applications is revisited.

Methods: This work presents a custom transmit-only quadrature birdcage, four-element receive coil array, and spectrometer interfaced to a commercial ONI 1.

Chemical Modifications of Porous Shape Memory Polymers for Enhanced X-ray and MRI Visibility.

The goal of this work was to develop a shape memory polymer (SMP) foam with visibility under both X-ray and magnetic resonance imaging (MRI) modalities. A porous polymeric material with these properties is desirable in medical device development for applications requiring thermoresponsive tissue scaffolds with clinical imaging capabilities. Dual modality visibility was achieved by chemically incorporating monomers with X-ray visible iodine-motifs and MRI visible monomers with gadolinium content.

Investigation of Low-Cost Op-Amps as Decoupling Preamplifiers for MRI Array Coils.

The benefits of array coils in MRI and MRS are well known. A key component of essentially all array coils used today is the decoupling preamplifier. Unlike conventional 50 ohm low-noise preamps, decoupling preamps present a reactive impedance to the coil, which can be used to 'block' currents from being induced in the receive coil, reducing the impact of any electromagnetic coupling between array elements.

A Frequency Translation System for Multi-Channel, Multi-Nuclear MR Spectroscopy.

Objective: Most MRI scanners are equipped to receive signals from H array coils but few support multi-channel reception for other nuclei. Using receive arrays can provide significant SNR benefits, usually exploited to enable accelerated imaging, but the extension of these arrays to non-H nuclei has received less attention because of the relative lack of broadband array receivers. Non-H nuclei often have low sensitivity and stand to benefit greatly from the increase in SNR that arrays can provide.

Feasibility of Using a 1T Extremity Scanner with a Four-Element Array to Detect P in the Human Calf.

The feasibility of conducting in vivo non-localized skeletal muscle P Magnetic Resonance Spectroscopy (MRS) with a low-cost extremity 1 Tesla magnet is demonstrated. We designed and built a transmit-only quadrature birdcage, four-element receive coil array, and employed a home-built spectrometer interfaced with a commercial ONI 1.0T magnet.

Multi-Tuned Cable Traps for Multinuclear MRI and MRS.

Objective: The method of pole-insertion for multi-tuning cable traps was studied for multinuclear MRI and MRS applications.

Methods: Relative efficiency of the different cable trap modes was studied as component values were varied and at four different magnetic field strengths. In all cases, efficiencies were compared to equivalent single-tuned designs.

Automated modification and fusion of voxel models to construct body phantoms with heterogeneous breast tissue: Application to MRI simulations.

Background: Human voxel models incorporating detailed anatomical features are vital tools for the computational evaluation of electromagnetic (EM) fields within the body. Besides whole-body human voxel models, phantoms representing smaller heterogeneous anatomical features are often employed; for example, localized breast voxel models incorporating fatty and fibroglandular tissues have been developed for a variety of EM applications including mammography simulation and dosimetry, magnetic resonance imaging (MRI), and ultra-wideband microwave imaging. However, considering wavelength effects, electromagnetic modeling of the breast at sub-microwave frequencies necessitates detailed breast phantoms in conjunction with whole-body voxel models.

Trap Design and Construction for High-Power Multinuclear Magnetic Resonance Experiments.

Performing multinuclear experiments requires one or more radiofrequency (RF) coils operating at both the proton and second-nucleus frequencies; however, inductive coupling between coils must be mitigated to retain proton sensitivity and coil tuning stability. The inclusion of trap circuits simplifies placement of multinuclear RF coils while maintaining inter-element isolation. Of the commonly investigated non-proton nuclei, perhaps the most technically demanding is carbon-13, particularly when applying a proton decoupling scheme to improve the resulting spectra.

Exploration of highly accelerated magnetic resonance elastography using high-density array coils.

Background: Magnetic resonance elastography (MRE) measures tissue mechanical properties by applying a shear wave and capturing its propagation using magnetic resonance imaging (MRI). By using high density array coils, MRE images are acquired using single echo acquisition (SEA) and at high resolutions with significantly reduced scan times.

Methods: Sixty-four channel uniplanar and 32×32 channel biplanar receive arrays are used to acquire MRE wave image sets from agar samples containing regions of varying stiffness.

A three-element 1H-31P dual-tuned array for magnetic resonance spectroscopy at 4.7 T.

This work describes the construction and testing of a three-element, double-tuned receive array and transmit coils for 31P-1H spectroscopy and imaging. The receive coils were geometrically-decoupled, single-loop surface coils and the transmit coils were concentric saddle coils. The coils were used to examine a physiologically-modeled CNC-milled phantom.

Effects of coplanar shielding for high field MRI.

This work investigates the efficacy of "coplanar shielding," in which copper shields are oriented concentric and coplanar to the RF coils rather than implemented as a full ground plane behind them. Following FDTD simulations to determine optimal shielding parameters, two coil geometries were constructed: a circular loop surface coil and a half-volume five-element receive array. Each was evaluated using bench measurements with and without coplanar shielding.

A Switched-Mode Breast Coil for 7 T MRI Using Forced-Current Excitation.

In high-field magnetic resonance imaging, the radio frequency wavelength within the human body is comparable to anatomical dimensions, resulting in B1 inhomogeneity and nonuniform sensitivity patterns. Thus, this relatively short wavelength presents engineering challenges for RF coil design. In this study, a bilateral breast coil for (1)H imaging at 7 T was designed and constructed using forced-current excitation.

Geometric decoupling of a mouse array coil using a dual plane pair design with crisscrossed return paths and custom mounting fixture.

An element design for receive array coils that decouples from the transmit coil without external active detuning is presented for magnetic resonance imaging (MRI) of mice. The array element uses a crisscrossed geometry on the return paths to reduce the current induced by the transmit coil. Without the need for an external active detune network, the proposed method simplifies the construction of MRI coil systems and also mitigates problems in space-limited MRI applications.

A 16-channel receive, forced current excitation dual-transmit coil for breast imaging at 7T.

Purpose: To enable high spatial and temporal breast imaging resolution via combined use of high field MRI, array coils, and forced current excitation (FCE) multi channel transmit.

Materials And Methods: A unilateral 16-channel receive array insert was designed for use in a transmit volume coil optimized for quadrature operation with dual-transmit RF shimming at 7 T. Signal-to-noise ratio (SNR) maps, g-factor maps, and high spatial and temporal resolution in vivo images were acquired to demonstrate the utility of the coil architecture.

An eight-channel T/R head coil for parallel transmit MRI at 3T using ultra-low output impedance amplifiers.

Parallel transmit is an emerging technology to address the technical challenges associated with MR imaging at high field strengths. When developing arrays for parallel transmit systems, one of the primary factors to be considered is the mechanism to manage coupling and create independently operating channels. Recent work has demonstrated the use of amplifiers to provide some or all of the channel-to-channel isolation, reducing the need for on-coil decoupling networks in a manner analogous to the use of isolation preamplifiers with receive coils.

Quadrature transmit coil for breast imaging at 7 tesla using forced current excitation for improved homogeneity.

Purpose: To demonstrate the use of forced current excitation (FCE) to create homogeneous excitation of the breast at 7 tesla, insensitive to the effects of asymmetries in the electrical environment.

Materials And Methods: FCE was implemented on two breast coils: one for quadrature (1) H imaging and one for proton-decoupled (13) C spectroscopy. Both were a Helmholtz-saddle combination, with the saddle tuned to 298 MHz for imaging and 75 MHz for spectroscopy.

A microfluidically cryocooled spiral microcoil with inductive coupling for MR microscopy.

Magnetic resonance (MR) microscopy typically employs microcoils for enhanced local signal-to-noise ratio (SNR). Planar (surface) microcoils, in particular, offer the potential to be configured into array elements as well as to enable the imaging of extremely small samples because of the uniformity and precision provided by microfabrication techniques. Microcoils, in general, however, are copper-loss dominant, and cryocooling methods have been successfully used to improve the SNR.

An insertable nonlinear gradient coil for phase compensation in SEA imaging.

In magnetic resonance imaging with array coils with many elements, as the radiofrequency (RF) coil dimensions approach the voxel dimensions, the phase gradient due to the magnetic field pattern of the coil causes signal cancellation within each voxel. In single echo acquisition (SEA) imaging with coil arrays, a gradient pulse can be applied to compensate for this effect. However, because RF coil phase varies with distance from the array and reverses on opposite sides of a dual-sided array, this method of phase compensation can be optimized for only a single slice at a time.

An Improved Element Design for 64-Channel Planar Imaging.

Investigation of highly accelerated MRI has developed into a lively corner in the hardware and methodology arena in recent years. At the extreme of (one-dimensional) acceleration, our group introduced Single Echo Acquisition (SEA) imaging, in which the need to phase encode a 64×N(readout) image is eliminated and replaced with the well-localized spatial information obtained from an array of 64 very narrow, long, parallel coils. The narrow coil width (2mm) that facilitates this is accompanied by a concomitant constraint on the useful imaging depth.

A parallel imaging approach to wide-field MR microscopy.

Magnetic resonance microscopy, suggested in the earliest papers on MRI, has always been limited by the low signal-to-noise ratio resulting from the small voxel size. Magnetic resonance microscopy has largely been enabled by the use of microcoils that provide the signal-to-noise ratio improvement required to overcome this limitation. Concomitant with the small coils is a small field-of-view, which limits the use of magnetic resonance microscopy as a histological tool or for imaging large regions in general.

A magnetic resonance (MR) microscopy system using a microfluidically cryo-cooled planar coil.

We present the development of a microfluidically cryo-cooled planar coil for magnetic resonance (MR) microscopy. Cryogenically cooling radiofrequency (RF) coils for magnetic resonance imaging (MRI) can improve the signal to noise ratio (SNR) of the experiment. Conventional cryostats typically use a vacuum gap to keep samples to be imaged, especially biological samples, at or near room temperature during cryo-cooling.

A desktop imaging system for teaching MR engineering.

This paper reports our results in developing a simple MRI system for teaching the basics of MR Engineering at the undergraduate or graduate level. LabVIEW data acquisition cards were used for generating and digitizing the RF signals and controlling gradients and transmit/receive and blanking switches. A very inexpensive and simple magnet reported previously by Sahakian was used to enable simple, projection reconstruction imaging.