A 16-Channel C Array Coil for Magnetic Resonance Spectroscopy of the Breast at 7T.

Objective: Considering the reported elevation of ω-6/ω-3 fatty acid ratios in breast neoplasms, one particularly important application of C MRS could be in more fully understanding the breast lipidome's relationship to breast cancer incidence. However, the low natural abundance and gyromagnetic ratio of the C isotope lead to detection sensitivity challenges. Previous C MRS studies have relied on the use of small surface coils with limited field-of-view and shallow penetration depths to achieve adequate signal-to-noise ratio (SNR), and the use of receive array coils is still mostly unexplored.

A retrofit to enable dynamic steering for transmit arrays without multiple amplifiers.

Purpose: shimming is an important method for mitigating B inhomogeneity in high-field MRI. Using independent power amplifiers for each transmit (Tx) element is the preferred method for B shimming but comes with a high cost. Conversely, the simplest approach to control a Tx array is by using coaxial cables of varying length in the Tx chain, but this approach is cumbersome and impractical for dynamic shimming.

A 32-channel receive array coil for bilateral breast imaging and spectroscopy at 7T.

Purpose: This work describes the construction and evaluation of a bilateral 32-channel receive array for breast imaging at 7T.

Methods: The receive array consisted of 32 receive coils, placed on two 3D-printed hemispherical formers. Each side of the receive array consisted of 16 receive loops, each loop having a corresponding detachable board with match/tune capacitors, active detuning circuitry, and a balun.

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.

An Adjustable-Length Dipole Using Forced-Current Excitation for 7T MR.

Ultrahigh field imaging of the body and the spine is challenging due to the large field-of-view (FOV) required. It is especially difficult for RF transmission due to its requirement on both the length and the depth of the ${\rm{B}}_{1}^{{\rm + }}$ field. One solution is to use a long dipole to provide continuous current distribution.

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.

Oxidation of [U- C]glucose in the human brain at 7T under steady state conditions.

Purpose: Disorders of brain energy metabolism and neurotransmitter recycling have been implicated in multiple neurological conditions. C magnetic resonance spectroscopy ( C MRS) during intravenous administration of C-labeled compounds has been used to measure turnover rates of brain metabolites. This approach, however, requires prolonged infusion inside the magnet.

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.

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.

Reproducibility and absolute quantification of muscle glycogen in patients with glycogen storage disease by 13C NMR spectroscopy at 7 Tesla.

Carbon-13 magnetic resonance spectroscopy (13C MRS) offers a noninvasive method to assess glycogen levels in skeletal muscle and to identify excess glycogen accumulation in patients with glycogen storage disease (GSD). Despite the clinical potential of the method, it is currently not widely used for diagnosis or for follow-up of treatment. While it is possible to perform acceptable 13C MRS at lower fields, the low natural abundance of 13C and the inherently low signal-to-noise ratio of 13C MRS makes it desirable to utilize the advantage of increased signal strength offered by ultra-high fields for more accurate measurements.

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.

Single-camera motion measurement and monitoring for magnetic resonance applications.

An optically based rigid-body six-degrees of freedom (DOF) measurement system optimized for prospective (real-time) motion correction in magnetic resonance imaging (MRI) applications is described. By optimizing system capabilities to the specific applications requirements, the six-DOF measurement is accomplished using a single camera and simple three-disc fiducial at rates of 50 Hz. The algorithm utilizes successive approximation to solve the three point pose problem for angles close to the origin.

Functional imaging and related techniques: an introduction for rehabilitation researchers.

Functional neuroimaging and related neuroimaging techniques are becoming important tools for rehabilitation research. Functional neuroimaging techniques can be used to determine the effects of brain injury or disease on brain systems related to cognition and behavior and to determine how rehabilitation changes brain systems. These techniques include: functional magnetic resonance imaging (fMRI), positron emission tomography (PET), electroencephalography (EEG), magnetoencephalography (MEG), near infrared spectroscopy (NIRS), and transcranial magnetic stimulation (TMS).

Optical head tracking for functional magnetic resonance imaging using structured light.

An accurate motion-tracking technique is needed to compensate for subject motion during functional magnetic resonance imaging (fMRI) procedures. Here, a novel approach to motion metrology is discussed. A structured light pattern specifically coded for digital signal processing is positioned onto a fiduciary of the patient.

Selective detrending method for reducing task-correlated motion artifact during speech in event-related FMRI.

Task-correlated motion artifacts that occur during functional magnetic resonance imaging can be mistaken for brain activity. In this work, a new selective detrending method for reduction of artifacts associated with task-correlated motion (TCM) during speech in event-related functional magnetic resonance imaging is introduced and demonstrated in an overt word generation paradigm. The performance of this new method is compared with that of three existing methods for reducing artifacts because of TCM: (1) motion parameter regression, (2) ignoring images during speech, and (3) detrending time course datasets of signal components related to TCM (deduced from artifact corrupted voxels).

Validation of non-rigid registration between functional and anatomical magnetic resonance brain images.

This paper presents a set of validation procedures for nonrigid registration of functional EPI to anatomical MRI brain images. Although various registration techniques have been developed and validated for high-resolution anatomical MRI images, due to a lack of quantitative and qualitative validation procedures, the use of nonrigid registration between functional EPI and anatomical MRI images has not yet been deployed in neuroimaging studies. In this paper, the performance of a robust formulation of a nonrigid registration technique is evaluated in a quantitative manner based on simulated data and is further evaluated in a quantitative and qualitative manner based on in vivo data as compared to the commonly used rigid and affine registration techniques in the neuroimaging software packages.