Axonal loss in major sensorimotor tracts is associated with impaired motor performance in minimally disabled multiple sclerosis patients.

Multiple sclerosis is a neuroinflammatory disease of the CNS that is associated with significant irreversible neuro-axonal loss, leading to permanent disability. There is thus an urgent need for markers of axonal loss for use in patient monitoring or as end-points for trials of neuroprotective agents. Advanced diffusion MRI can provide markers of diffuse loss of axonal fibre density or atrophy within specific white matter pathways.

Ultra-High Field Magnetic Resonance Imaging of the Retrobulbar Optic Nerve, Subarachnoid Space, and Optic Nerve Sheath in Emmetropic and Myopic Eyes.

Purpose: We aimed to image the optic nerve, subarachnoid space and optic nerve sheath in emmetropes and myopes ultra-high field (7-Tesla) magnetic resonance imaging (MRI). We targeted the retrobulbar distance of approximately 3 mm behind the eyeball, an area of clinical interest because of optic nerve sheath distensibility and pressure-related enlargement.

Methods: Eleven emmetropes (+0.

Functional correlates of motor control impairments in multiple sclerosis: A 7 Tesla task functional MRI study.

Upper and lower limb impairments are common in people with multiple sclerosis (pwMS), yet difficult to clinically identify in early stages of disease progression. Tasks involving complex motor control can potentially reveal more subtle deficits in early stages, and can be performed during functional MRI (fMRI) acquisition, to investigate underlying neural mechanisms, providing markers for early motor progression. We investigated brain activation during visually guided force matching of hand or foot in 28 minimally disabled pwMS (Expanded Disability Status Scale (EDSS) < 4 and pyramidal and cerebellar Kurtzke Functional Systems Scores ≤ 2) and 17 healthy controls (HC) using ultra-high field 7-Tesla fMRI, allowing us to visualise sensorimotor network activity in high detail.

Head and neck manifestations of granulomatosis with polyangiitis.

Granulomatosis with polyangiitis is a rare autoimmune condition which causes respiratory tract granulomas, small to medium vessel vasculitis and renal disease. Head and neck manifestations are some of the most common presentations of the condition, with a significant proportion of patients experiencing sinonasal disease alone. The recognition of suggestive imaging findings, in combination with clinical history and serology, aids the diagnosis and appropriate treatment.

MR-EYE: High-Resolution MRI of the Human Eye and Orbit at Ultrahigh Field (7T).

Ultrahigh-field (7T) MRI provides improved contrast and a signal-to-noise gain compared with lower magnetic field strengths. Here, we demonstrate feasibility and optimization of anatomic imaging of the eye and orbit using a dedicated commercial multichannel transmit and receive eye coil. Optimization of participant setup techniques and MRI sequence parameters allowed for improvements in the image resolution and contrast, and the eye and orbit coverage with minimal susceptibility and motion artifacts in a clinically feasible protocol.

Substantially thinner internal granular layer and reduced molecular layer surface in the cerebellar cortex of the Tc1 mouse model of down syndrome - a comprehensive morphometric analysis with active staining contrast-enhanced MRI.

Down Syndrome is a chromosomal disorder that affects the development of cerebellar cortical lobules. Impaired neurogenesis in the cerebellum varies among different types of neuronal cells and neuronal layers. In this study, we developed an imaging analysis framework that utilizes gadolinium-enhanced ex vivo mouse brain MRI.

An Experimental Investigation of White Matter Venous Hemodynamics: Basic Physiology and Disruption in Neuroinflammatory Disease.

The white matter is highly vascularised by the cerebral venous system. In this paper, we describe a unique blood oxygen-level dependent (BOLD) signal within the white matter using functional MRI and spatial independent components analysis. The signal is characterized by a narrow peak frequency band between 0.

Microstructural correlates of Na relaxation in human brain at 7 Tesla.

Na provides the second strongest MR-observable signal in biological tissue and exhibits bi-exponential T relaxation in micro-environments such as the brain. There is significant interest in developing Na biomarkers for neurological diseases that are associated with sodium channel dysfunction such as multiple sclerosis and epilepsy. We have previously reported methods for acquisition of multi-echo sodium MRI and continuous distribution modelling of sodium relaxation properties as surrogate markers of brain microstructure.

Extracting more for less: multi-echo MP2RAGE for simultaneous T -weighted imaging, T mapping, mapping, SWI, and QSM from a single acquisition.

Purpose: To demonstrate simultaneous T -weighted imaging, T mapping, mapping, SWI, and QSM from a single multi-echo (ME) MP2RAGE acquisition.

Methods: A single-echo (SE) MP2RAGE sequence at 7 tesla was extended to ME with 4 bipolar gradient echo readouts. T -weighted images and T maps calculated from individual echoes were combined using sum of squares and averaged, respectively.

Compressed sensing effects on quantitative analysis of undersampled human brain sodium MRI.

Purpose: The clinical application of sodium MRI is hampered due to relatively low image quality and associated long acquisition times. Compressed sensing (CS) aims at a reduction of measurement time, but has been found to encompass quantitative estimation bias when used in low SNR x-Nuclei imaging. This work analyses CS in quantitative human brain sodium MRI from undersampled acquisitions and provides recommendations for tissue sodium concentration (TSC) estimation.

A continuum of components: Flexible fast fraction mapping in sodium MRI.

Purpose: Parameter mapping in sodium MRI data is challenging due to inherently low SNR and spatial resolution, prompting the need to employ robust models and estimation techniques. This work aims to develop a continuum model of sodium -decay to overcome the limitations of the commonly employed bi-exponential models. Estimates of mean -decay and fast component fraction in tissue are emergent from the inferred continuum model.

Zero-gradient-excitation ramped hybrid encoding (zG -RHE) sodium MRI.

Purpose: Fast bi-exponential transverse signal decay compounds sodium image quality. This work aims at enhancing image characteristics using a special case of ramped hybrid encoding (RHE). Zero-gradient-excitation (zG )-RHE provides (1) gradient-free excitation for high flip angle, artifact-free excitation profiles and (2) gradient ramping during dead-time for the optimization of encoding time (t ) to reduce T signal decay influence during acquisition.

Optimized partial-coverage functional analysis pipeline (OPFAP): a semi-automated pipeline for skull stripping and co-registration of partial-coverage, ultra-high-field functional images.

Objective: Ultra-high-field functional MRI (UHF-fMRI) allows for higher spatiotemporal resolution imaging. However, higher-resolution imaging entails coverage limitations. Processing partial-coverage images using standard pipelines leads to sub-optimal results.

3D-multi-echo radial imaging of Na (3D-MERINA) for time-efficient multi-parameter tissue compartment mapping.

Purpose: This work demonstrates a 3D radial multi-echo acquisition scheme for time-efficient sodium ( Na) MR-signal acquisition and analysis. Echo reconstructions were used to produce signal-to-noise ratio (SNR)-enhanced Na-images and parameter maps of the biexponential observed transverse relaxation time ( T2*) decay.

Methods: A custom-built sequence for radial multi-echo acquisition was proposed for acquisition of a series of 3D volumetric Na-images.

7T-fMRI: Faster temporal resolution yields optimal BOLD sensitivity for functional network imaging specifically at high spatial resolution.

Recent developments in accelerated imaging methods allow faster acquisition of high spatial resolution images. This could improve the applications of functional magnetic resonance imaging at 7 Tesla (7T-fMRI), such as neurosurgical planning and Brain Computer Interfaces (BCIs). However, increasing the spatial and temporal resolution will both lead to signal-to-noise ratio (SNR) losses due to decreased net magnetization per voxel and T-relaxation effect, respectively.

Fully-Automated μMRI Morphometric Phenotyping of the Tc1 Mouse Model of Down Syndrome.

We describe a fully automated pipeline for the morphometric phenotyping of mouse brains from μMRI data, and show its application to the Tc1 mouse model of Down syndrome, to identify new morphological phenotypes in the brain of this first transchromosomic animal carrying human chromosome 21. We incorporate an accessible approach for simultaneously scanning multiple ex vivo brains, requiring only a 3D-printed brain holder, and novel image processing steps for their separation and orientation. We employ clinically established multi-atlas techniques-superior to single-atlas methods-together with publicly-available atlas databases for automatic skull-stripping and tissue segmentation, providing high-quality, subject-specific tissue maps.

The significance of incidental brain uptake on 68Ga-DOTATATE PET-CT in neuroendocrine tumour patients.

Objective: Radiolabelled somatostatin analogues detect neuroendocrine tumours (NETs), but may reveal other tumour types. We examined the prevalence of possible meningioma in patients with known or suspected NETs imaged with Ga-DOTATATE PET-computed tomography (CT) on the basis of central nervous system uptake and compared with findings on magnetic resonance and contrast-enhanced CT imaging.

Methods: Retrospective imaging reports from 313 patients who had undergone Ga-DOTATATE PET imaging for primary or repeat NET staging were searched to identify suspected meningiomas on PET.

Diffusion microscopic MRI of the mouse embryo: Protocol and practical implementation in the splotch mouse model.

Purpose: Advanced methodologies for visualizing novel tissue contrast are essential for phenotyping the ever-increasing number of mutant mouse embryos being generated. Although diffusion microscopic MRI (μMRI) has been used to phenotype embryos, widespread routine use is limited by extended scanning times, and there is no established experimental procedure ensuring optimal data acquisition.

Methods: We developed two protocols for designing experimental procedures for diffusion μMRI of mouse embryos, which take into account the effect of embryo preparation and pulse sequence parameters on resulting data.

Enhanced tissue differentiation in the developing mouse brain using magnetic resonance micro-histology.

Purpose: Worldwide efforts to understand developmental processes demand new high-resolution 3D imaging methods to detect the consequences of gene function in embryo development and diseases. Encouragingly, recent studies have shown that MRI contrast agents can highlight specific tissue structures in ex vivo adult mouse brains. MR imaging of mouse embryos is currently limited by a lack of tissue staining capabilities that would provide the flexibility and specificity offered by histological stains conventionally used for mouse embryo phenotyping.

Segmentation propagation using a 3D embryo atlas for high-throughput MRI phenotyping: comparison and validation with manual segmentation.

Effective methods for high-throughput screening and morphometric analysis are crucial for phenotyping the increasing number of mouse mutants that are being generated. Automated segmentation propagation for embryo phenotyping is an emerging application that enables noninvasive and rapid quantification of substructure volumetric data for morphometric analysis. We present a study to assess and validate the accuracy of brain and kidney volumes generated via segmentation propagation in an ex vivo mouse embryo MRI atlas comprising three different groups against the current "gold standard"--manual segmentation.

Structural correlates of active-staining following magnetic resonance microscopy in the mouse brain.

Extensive worldwide efforts are underway to produce knockout mice for each of the ~25,000 mouse genes, which may give new insights into the underlying pathophysiology of neurological disease. Microscopic magnetic resonance imaging (μMRI) is a key method for non-invasive morphological phenotyping, capable of producing high-resolution 3D images of ex-vivo brains, after fixation with an MR contrast agent. These agents have been suggested to act as active-stains, enhancing structures not normally visible on MRI.

Comparison of segmentation methods for MRI measurement of cardiac function in rats.

Purpose: To establish the accuracy, intra- and inter-observer variabilities of four different segmentation methods for measuring cardiac functional parameters in healthy and infarcted rat hearts.

Materials And Methods: Six Wistar rats were imaged before and after myocardial infarction using an electrocardiogram and respiratory-gated spoiled gradient echo sequence. Blinded and randomized datasets were analyzed by various semi-automatic and manual segmentation methods to compare their measurement bias and variability.

Magnetic resonance virtual histology for embryos: 3D atlases for automated high-throughput phenotyping.

Ambitious international efforts are underway to produce gene-knockout mice for each of the 25,000 mouse genes, providing a new platform to study mammalian development and disease. Robust, large-scale methods for morphological assessment of prenatal mice will be essential to this work. Embryo phenotyping currently relies on histological techniques but these are not well suited to large volume screening.