On the use of multi-echo NODDI MRI with released intrinsic diffusivity for the assessment of tissue diffusion and relaxation properties in experimental ischaemic stroke.

The multi-echo neurite orientation dispersion and density imaging (MTE-NODDI) model has been proposed to overcome one of the shortcomings of conventional NODDI, namely the echo time (TE) dependence of the compartmental signal fractions, which stems from the intrinsic differences in the compartmental transverse relaxation times (T2). However, the model continues to be constrained by the limitation of having a fixed, brain-wide intrinsic diffusivity, d. The primary aim of this work is to assess the benefits and shortcomings of using MTE-NODDI to investigate the diffusion and T2 properties of ischaemic stroke tissue following middle cerebral artery occlusion (MCAo) in rat models.

7-Tesla ultra-high field MRI of the parahippocampal cortex reveals evidence of common neurobiological mechanisms of major depressive disorder and neurotic personality traits.

The parahippocampal cortex (PHC) is a highly interconnected region within the medial temporal lobe (MTL) and is essential in memory, emotion and cognition. According to the cognitive model of depression, dysfunctions in these processes constitute the pathophysiological foundation of major depressive disorder (MDD). Research suggests that human personality, and neuroticism in particular, plays an important role in the development and disease progression of MDD.

Development of an echo-shifted, multi-echo, gradient-echo sequence for T* quantification of slow-relaxing water pools.

Purpose: Although conventional multi-echo gradient-echo (GRE) sequences effectively quantify short and intermediate T* in brain tissue, and general interest in cerebrospinal fluid (CSF) is growing due to its association with the glymphatic system, quantifying T* in CSF remains underexplored. Accurate quantification of the slow-relaxing water pools requires imaging at long echo times, significantly increasing acquisition time. This study proposes a novel sequence capable of quantifying the entire range of T* without prolonged acquisition time, mapping T* in both CSF and brain tissue.

Novel H/F double-tuned coil using an asymmetrical butterfly coil.

Background: Fluorine-19 (F) magnetic resonance imaging (MRI) is a non-invasive imaging tool for the targeted application of fluorinated agents, such as cell tracking, and for the demonstration of oximetry. However, as the SNR of F is significantly weaker than that of proton (H) imaging, the F coil must be combined with H coils for anatomical co-registration and B shimming. This is difficult due to the strong coupling between the coils when they are in proximity, and is problematic since the Larmor frequency of F is 94% that of H, further increasing the potential for coupling between the H and F elements.

Brain Tumor Characterization Using Multiple MR Parameters From Multi-Contrast EPI With Keyhole (GE-SE EPIK) Including Oxygen Extraction Fraction: A Comparison to O-(2-[18F]Fluoroethyl)-L-Tyrosine (FET) Positron Emission Tomography.

Background: Tumor characterization and treatment efficacy are associated with tissue hypoxia. MR-derived oxygen extraction fraction (OEF) may offer valuable tumor insights but depends on multiple measurement parameters, often requiring multiple sequence acquisitions. Specific multi-parametric sequences offer direct access to MR parameter sets within short acquisition times.

A study of long-term GABA and high-energy phosphate alterations in the primary motor cortex using anodal tDCS and H/P MR spectroscopy.

Introduction: Anodal transcranial direct current stimulation (tDCS) has been reported to modulate gamma-aminobutyric acid levels and cerebral energy consumption in the brain. This study aims to investigate long-term GABA and cerebral energy modulation following anodal tDCS over the primary motor cortex.

Method: To assess GABA and energy level changes, proton and phosphorus magnetic resonance spectroscopy data were acquired before and after anodal or sham tDCS.

Structural alterations as a predictor of depression - a 7-Tesla MRI-based multidimensional approach.

Major depressive disorder (MDD) is a debilitating condition that is associated with changes in the default-mode network (DMN). Commonly reported features include alterations in gray matter volume (GMV), cortical thickness (CoT), and gyrification. A comprehensive examination of these variables using ultra-high field strength MRI and machine learning methods may lead to novel insights into the pathophysiology of depression and help develop a more personalized therapy.

High dynamic range mapping for the evaluation of parallel transmit arrays.

Purpose: Demonstration of a high dynamic-range and high SNR method for acquiring absolute maps from a combination of gradient echo and actual-flip-angle measurements that is especially useful during the construction of parallel-transmit arrays.

Methods: Low flip angle gradient echo images, acquired when transmitting with each channel individually, are used to compute relative maps. Instead of computing these in a conventional manner, the equivalence of the problem to the ESPIRiT parallel image reconstruction method is used to compute maps with a higher SNR.

Design, construction, and use of a tapered-spiral, quadrature H/Na double-tuned coil for in ovo MRI at 7 T.

Background: In ovo MR presents a promising and viable alternative to traditional in vivo small animal experiments. Sodium MRI complements proton MRI by providing potential access to tissue cellular metabolism. Despite its abundance, sodium MRI is challenged by lower MR sensitivity and faster relaxation times compared to proton MRI.

QRAGE-Simultaneous multiparametric quantitative MRI of water content, T, T*, and magnetic susceptibility at ultrahigh field strength.

Purpose: To introduce quantitative rapid gradient-echo (QRAGE), a novel approach for the simultaneous mapping of multiple quantitative MRI parameters, including water content, T, T*, and magnetic susceptibility at ultrahigh field strength.

Methods: QRAGE leverages a newly developed multi-echo MPnRAGE sequence, facilitating the acquisition of 171 distinct contrast images across a range of TI and TE points. To maintain a short acquisition time, we introduce MIRAGE2, a novel model-based reconstruction method that exploits prior knowledge of temporal signal evolution, represented as damped complex exponentials.

A Modified Quadrature Birdcage Coil Incorporated With a Curved Feature for MR Imaging.

This study presents a novel MRI coil design approach explicitly tailored for chick embryo measurements, with the primary objective of improving sensitivity and coverage. The limitations posed by conventional birdcage coils were addressed by introducing a curvature feature into a standard coil. The performance of the modified coil was assessed using EM simulations and experimental evaluations, which were subsequently validated using a 7 T MRI scanner.

Predicting performance in attention by measuring key metabolites in the PCC with 7T MRS.

The posterior cingulate cortex (PCC) is a key hub of the default mode network and is known to play an important role in attention. Using ultra-high field 7 Tesla magnetic resonance spectroscopy (MRS) to quantify neurometabolite concentrations, this exploratory study investigated the effect of the concentrations of myo-inositol (Myo-Ins), glutamate (Glu), glutamine (Gln), aspartate or aspartic acid (Asp) and gamma-amino-butyric acid (GABA) in the PCC on attention in forty-six healthy participants. Each participant underwent an MRS scan and cognitive testing, consisting of a trail-making test (TMT A/B) and a test of attentional performance.

Phenomena of hypo- and hyperconnectivity in basal ganglia-thalamo-cortical circuits linked to major depression: a 7T fMRI study.

Major depressive disorder (MDD) typically manifests itself in depressed affect, anhedonia, low energy, and additional symptoms. Despite its high global prevalence, its pathophysiology still gives rise to questions. Current research places alterations in functional connectivity among MDD's most promising biomarkers.

Spatiotemporal Patterns of White Matter Maturation after Pre-Adolescence: A Diffusion Kurtosis Imaging Study.

Diffusion tensor imaging (DTI) enables the assessment of changes in brain tissue microstructure during maturation and ageing. In general, patterns of cerebral maturation and decline render non-monotonic lifespan trajectories of DTI metrics with age, and, importantly, the rate of microstructural changes is heterochronous for various white matter fibres. Recent studies have demonstrated that diffusion kurtosis imaging (DKI) metrics are more sensitive to microstructural changes during ageing compared to those of DTI.

Aberrant Functional Connectivity of the Salience Network in Adult Patients with Tic Disorders: A Resting-State fMRI Study.

Tic disorders (TD) are characterized by the presence of motor and/or vocal tics. Common neurophysiological frameworks suggest dysregulations of the cortico-striatal-thalamo-cortical (CSTC) brain circuit that controls movement execution. Besides common tics, there are other "non-tic" symptoms that are primarily related to sensory perception, sensorimotor integration, attention, and social cognition.

High Spatiotemporal Resolution Radial Encoding Single-Vessel fMRI.

High-field preclinical functional MRI (fMRI) is enabled the high spatial resolution mapping of vessel-specific hemodynamic responses, that is single-vessel fMRI. In contrast to investigating the neuronal sources of the fMRI signal, single-vessel fMRI focuses on elucidating its vascular origin, which can be readily implemented to identify vascular changes relevant to vascular dementia or cognitive impairment. However, the limited spatial and temporal resolution of fMRI is hindered hemodynamic mapping of intracortical microvessels.

Impact of improved dead time correction on the quantification accuracy of a dedicated BrainPET scanner.

Objective: Quantitative values derived from PET brain images are of high interest for neuroscientific applications. Insufficient DT correction (DTC) can lead to a systematic bias of the output parameters obtained by a detailed analysis of the time activity curves (TACs). The DTC method currently used for the Siemens 3T MR BrainPET insert is global, i.

Accelerated multiple-quantum-filtered sodium magnetic resonance imaging using compressed sensing at 7 T.

Purpose: Multiple-quantum-filtered (MQF) sodium magnetic resonance imaging (MRI), such as enhanced single-quantum and triple-quantum-filtered imaging of Na (eSISTINA), enables images to be weighted towards restricted sodium, a promising biomarker in clinical practice, but often suffers from clinically infeasible acquisition times and low image quality. This study aims to mitigate the above limitation by implementing a novel eSISTINA sequence at 7 T with the application of compressed sensing (CS) to accelerate eSISTINA acquisitions without a noticeable loss of information.

Methods: A novel eSISTINA sequence with a 3D spiral-based sampling scheme was implemented at 7 T for the application of CS.

In Vivo Measurement of Rat Brain Water Content at 9.4 T MR Using Super-Resolution Reconstruction: Validation With Ex Vivo Experiments.

Background: Given that changes in brain water content are often correlated with disease, investigating water content non-invasively and in vivo could lead to a better understanding of the pathogenesis of several neurologic diseases.

Purpose: To adapt a super-resolution-based technique, previously developed for humans, to the rat brain and report in vivo high-resolution (HR) water content maps in comparison with ex vivo wet/dry methods.

Study Type: Prospective.

GABA receptor availability relates to emotion-induced BOLD responses in the medial prefrontal cortex: simultaneous fMRI/PET with [C]flumazenil.

Introduction: The fMRI BOLD response to emotional stimuli highlighting the role of the medial prefrontal cortex (MPFC) has been thoroughly investigated. Recently, the relationship between emotion processing and GABA levels has been studied using MPFC proton magnetic resonance spectroscopy (1H-MRS). However, the role of GABAA receptors in the MPFC during emotion processing remains unexplored.

Submillimeter fMRI Acquisition Techniques for Detection of Laminar and Columnar Level Brain Activation.

Since the first demonstration in the early 1990s, functional MRI (fMRI) has emerged as one of the most powerful, noninvasive neuroimaging tools to probe brain functions. Subsequently, fMRI techniques have advanced remarkably, enabling the acquisition of functional signals with a submillimeter voxel size. This innovation has opened the possibility of investigating subcortical neural activities with respect to the cortical depths or cortical columns.

Fronto-striatal dynamic connectivity is linked to dopaminergic motor response in Parkinson's disease.

Introduction: Differences in dopaminergic motor response in Parkinson's disease (PD) patients can be related to PD subtypes, and previous fMRI studies associated dopaminergic motor response with corticostriatal functional connectivity. While traditional fMRI analyses have assessed the mean connectivity between regions of interest, an important aspect driving dopaminergic response might lie in the temporal dynamics in corticostriatal connections.

Methods: This study aims to determine if altered resting-state dynamic functional network connectivity (DFC) is associated with dopaminergic motor response.