Macromolecule Modelling for Improved Metabolite Quantification Using Short Echo Time Brain H-MRS at 3 T and 7 T: The PRaMM Model.

To improve reliability of metabolite quantification at both, 3 T and 7 T, we propose a novel parametrized macromolecules quantification model (PRaMM) for brain H MRS, in which the ratios of macromolecule peak intensities are used as soft constraints. Full- and metabolite-nulled spectra were acquired in three different brain regions with different ratios of grey and white matter from six healthy volunteers, at both 3 T and 7 T. Metabolite-nulled spectra were used to identify highly correlated macromolecular signal contributions and estimate the ratios of their intensities.

Plasma p-tau181 and GFAP reflect 7T MR-derived changes in Alzheimer's disease: A longitudinal study of structural and functional MRI and MRS.

Background: Associations between longitudinal changes of plasma biomarkers and cerebral magnetic resonance (MR)-derived measurements in Alzheimer's disease (AD) remain unclear.

Methods: In a study population (n = 127) of healthy older adults and patients within the AD continuum, we examined associations between longitudinal plasma amyloid beta 42/40 ratio, tau phosphorylated at threonine 181 (p-tau181), glial fibrillary acidic protein (GFAP), neurofilament light chain (NfL), and 7T structural and functional MR imaging and spectroscopy using linear mixed models.

Results: Increases in both p-tau181 and GFAP showed the strongest associations to 7T MR-derived measurements, particularly with decreasing parietal cortical thickness, decreasing connectivity of the salience network, and increasing neuroinflammation as determined by MR spectroscopy (MRS) myo-inositol.

Macromolecule modelling for improved metabolite quantification using short echo time brain H MRS at 3 T and 7 T: The PRaMM Model.

Purpose: To improve reliability of metabolite quantification at both, 3 T and 7 T, we propose a novel parametrized macromolecules quantification model (PRaMM) for brain H MRS, in which the ratios of macromolecule peak intensities are used as soft constraints.

Methods: Full- and metabolite-nulled spectra were acquired in three different brain regions with different ratios of grey and white matter from six healthy volunteers, at both 3 T and 7 T. Metabolite-nulled spectra were used to identify highly correlated macromolecular signal contributions and estimate the ratios of their intensities.

Quantitative MR Image Reconstruction Using Parameter-Specific Dictionary Learning With Adaptive Dictionary-Size and Sparsity-Level Choice.

Objective: We propose a method for the reconstruction of parameter-maps in Quantitative Magnetic Resonance Imaging (QMRI).

Methods: Because different quantitative parameter-maps differ from each other in terms of local features, we propose a method where the employed dictionary learning (DL) and sparse coding (SC) algorithms automatically estimate the optimal dictionary-size and sparsity level separately for each parameter-map. We evaluated the method on a T-mapping QMRI problem in the brain using the BrainWeb data as well as in-vivo brain images acquired on an ultra-high field 7 T scanner.

7T amygdala and hippocampus subfields in volumetry-based associations with memory: A 3-year follow-up study of early Alzheimer's disease.

Introduction: The hippocampus is the most prominent single region of interest (ROI) for the diagnosis and prediction of Alzheimer's disease (AD). However, its suitability in the earliest stages of cognitive decline, i.e.

Fourier-based decomposition for simultaneous 2-voxel MRS acquisition with 2SPECIAL.

Purpose: To simultaneously acquire spectroscopic signals from two MRS voxels using a multi-banded 2 spin-echo, full-intensity acquired localized (2SPECIAL) sequence, and to decompose the signal to their respective regions by a novel voxel-GRAPPA (vGRAPPA) decomposition approach for in vivo brain applications at 7 T.

Methods: A wideband, uniform rate, smooth truncation (WURST) multi-banded pulse was incorporated into SPECIAL to implement 2SPECIAL for simultaneous multi-voxel spectroscopy (sMVS). To decompose the acquired data, the voxel-GRAPPA decomposition algorithm is introduced, and its performance is compared to the SENSE-based decomposition.

Assessment of measurement precision in single-voxel spectroscopy at 7 T: Toward minimal detectable changes of metabolite concentrations in the human brain in vivo.

Purpose: To introduce a study design and statistical analysis framework to assess the repeatability, reproducibility, and minimal detectable changes (MDCs) of metabolite concentrations determined by in vivo MRS.

Methods: An unbalanced nested study design was chosen to acquire in vivo MRS data within different repeatability and reproducibility scenarios. A spin-echo, full-intensity acquired localized (SPECIAL) sequence was employed at 7 T utlizing three different inversion pulses: a hyperbolic secant (HS), a gradient offset independent adiabaticity (GOIA), and a wideband, uniform rate, smooth truncation (WURST) pulse.

Pentafluorosulfanyl (SF) as a Superior F Magnetic Resonance Reporter Group: Signal Detection and Biological Activity of Teriflunomide Derivatives.

Fluorine (F) magnetic resonance imaging (MRI) is severely limited by a low signal-to noise ratio (SNR), and tapping it for F drug detection in vivo still poses a significant challenge. However, it bears the potential for label-free theranostic imaging. Recently, we detected the fluorinated dihydroorotate dehydrogenase (DHODH) inhibitor teriflunomide (TF) noninvasively in an animal model of multiple sclerosis (MS) using F MR spectroscopy (MRS).

Frequency drift in MR spectroscopy at 3T.

Purpose: Heating of gradient coils and passive shim components is a common cause of instability in the B field, especially when gradient intensive sequences are used. The aim of the study was to set a benchmark for typical drift encountered during MR spectroscopy (MRS) to assess the need for real-time field-frequency locking on MRI scanners by comparing field drift data from a large number of sites.

Method: A standardized protocol was developed for 80 participating sites using 99 3T MR scanners from 3 major vendors.

detection of teriflunomide-derived fluorine signal during neuroinflammation using fluorine MR spectroscopy.

Magnetic resonance imaging (MRI) is indispensable for diagnosing neurological conditions such as multiple sclerosis (MS). MRI also supports decisions regarding the choice of disease-modifying drugs (DMDs). Determining tissue concentrations of DMDs has the potential to become an essential clinical tool for therapeutic drug monitoring (TDM).

Metabolite cycled liver H MRS on a 7 T parallel transmit system.

Introduction: Single-voxel H MRS in body applications often suffers from respiratory and other motion induced phase and frequency shifts, which lead to incoherent averaging and hence to suboptimal results.

Methods: Here we show the application of metabolite cycling (MC) for liver STEAM-localized H MRS on a 7 T parallel transmit system, using eight transmit-receive fractionated dipole antennas with 16 additional, integrated receive loops. MC-STEAM measurements were made in six healthy, lean subjects and compared with STEAM measurements using VAPOR water suppression.

European Ultrahigh-Field Imaging Network for Neurodegenerative Diseases (EUFIND).

Introduction: The goal of European Ultrahigh-Field Imaging Network in Neurodegenerative Diseases (EUFIND) is to identify opportunities and challenges of 7 Tesla (7T) MRI for clinical and research applications in neurodegeneration. EUFIND comprises 22 European and one US site, including over 50 MRI and dementia experts as well as neuroscientists.

Methods: EUFIND combined consensus workshops and data sharing for multisite analysis, focusing on 7 core topics: clinical applications/clinical research, highest resolution anatomy, functional imaging, vascular systems/vascular pathology, iron mapping and neuropathology detection, spectroscopy, and quality assurance.

Non-Water-Suppressed H MR Spectroscopy with Orientational Prior Knowledge Shows Potential for Separating Intra- and Extramyocellular Lipid Signals in Human Myocardium.

Conditions such as type II diabetes are linked with elevated lipid levels in the heart, and significantly increased risk of heart failure; however, metabolic processes underlying the development of cardiac disease in type II diabetes are not fully understood. Here we present a non-invasive method for in vivo investigation of cardiac lipid metabolism: namely, IVS-McPRESS. This technique uses metabolite-cycled, non-water suppressed H cardiac magnetic resonance spectroscopy with prospective and retrospective motion correction.

A comparison of optimization algorithms for localized in vivo B shimming.

Purpose: To compare several different optimization algorithms currently used for localized in vivo B shimming, and to introduce a novel, fast, and robust constrained regularized algorithm (ConsTru) for this purpose.

Methods: Ten different optimization algorithms (including samples from both generic and dedicated least-squares solvers, and a novel constrained regularized inversion method) were implemented and compared for shimming in five different shimming volumes on 66 in vivo data sets from both 7 T and 9.4 T.

Mechanisms of SNR and line shape improvement by B correction in overdiscrete MRSI reconstruction.

Purpose: Inhomogeneities of the main magnetic field cause line broadening and location-dependent frequency shifts in brain MRSI. These are often visible despite advanced B shimming. The purpose of this work is to propose an advanced B correction method that can easily be applied during postprocessing.

Fast iterative pre-emphasis calibration method enabling third-order dynamic shim updated fMRI.

Purpose: To calibrate a pre-emphasis to sufficiently compensate eddy currents for application of dynamic shim updating to fMRI without extension of scan times.

Methods: Eddy current effects induced into all shim terms up to third-order were characterized by spatiotemporal field monitoring, using a third-order field camera. Pre-emphasis settings were derived from the measurements and iteratively evaluated and refined.

Constrained image-based B0 shimming accounting for "local minimum traps" in the optimization and field inhomogeneities outside the region of interest.

Purpose: To improve B0 shimming for applications in high- and ultrahigh-field magnetic resonance imaging and magnetic resonance spectroscopy.

Methods: An existing image-based constrained B0 shimming algorithm was enhanced using two techniques: (1) A region of less interest was introduced to control B0 field inhomogeneities in the vicinity of the region of interest; (2) multiple sets of starting values were used for the fitting routine, to avoid "getting trapped" in a local minimum of the optimization function. The influence of constraints during the fitting procedure, due to hardware limitations, on the B0 shim result was investigated.

Reduction of voxel bleeding in highly accelerated parallel (1) H MRSI by direct control of the spatial response function.

Purpose: To substantially improve spatial localization in magnetic resonance spectroscopic imaging (MRSI) accelerated by parallel imaging. This is important in order to make MRSI more reliable as a tool for clinical applications.

Methods: The sensitivity encoding acceleration technique with spatial overdiscretization is applied for the reconstruction of parallel MRSI.

Dielectric response of deeply supercooled hydration water in the connective tissue proteins collagen and elastin.

The low-temperature dielectric relaxation of collagen and elastin was studied over a wide range of hydrations h. The hydration-shell response increases weakly with temperature, is thermally activated, and conforms to energy barrier scaling. This demonstrates the existence of a decoupled, secondary relaxation akin to that in binary structural glasses.