RF shimming in the cervical spinal cord at 7 T.

Purpose: Advancing the development of 7 T MRI for spinal cord imaging is crucial for the enhanced diagnosis and monitoring of various neurodegenerative diseases and traumas. However, a significant challenge at this field strength is the transmit field inhomogeneity. Such inhomogeneity is particularly problematic for imaging the small, deep anatomical structures of the cervical spinal cord, as it can cause uneven signal intensity and elevate the local specific absorption ratio, compromising image quality.

Reproducible Research Practices in Magnetic Resonance Neuroimaging: A Review Informed by Advanced Language Models.

MRI has progressed significantly with the introduction of advanced computational methods and novel imaging techniques, but their wider adoption hinges on their reproducibility. This concise review synthesizes reproducible research insights from recent MRI articles to examine the current state of reproducibility in neuroimaging, highlighting key trends and challenges. It also provides a custom generative pretrained transformer (GPT) model, designed specifically for aiding in an automated analysis and synthesis of information pertaining to the reproducibility insights associated with the articles at the core of this review.

Repeat it without me: Crowdsourcing the T mapping common ground via the ISMRM reproducibility challenge.

Purpose: T mapping is a widely used quantitative MRI technique, but its tissue-specific values remain inconsistent across protocols, sites, and vendors. The ISMRM Reproducible Research and Quantitative MR study groups jointly launched a challenge to assess the reproducibility of a well-established inversion-recovery T mapping technique, using acquisition details from a seminal T mapping paper on a standardized phantom and in human brains.

Methods: The challenge used the acquisition protocol from Barral et al.

qMRI-BIDS: An extension to the brain imaging data structure for quantitative magnetic resonance imaging data.

The Brain Imaging Data Structure (BIDS) established community consensus on the organization of data and metadata for several neuroimaging modalities. Traditionally, BIDS had a strong focus on functional magnetic resonance imaging (MRI) datasets and lacked guidance on how to store multimodal structural MRI datasets. Here, we present and describe the BIDS Extension Proposal 001 (BEP001), which adds a range of quantitative MRI (qMRI) applications to the BIDS.

Reduced Axon Calibre in the Associative Striatum of the Knockout Mouse.

Pathological repetitive behaviours are a common feature of various neuropsychiatric disorders, including compulsions in obsessive-compulsive disorder or tics in Gilles de la Tourette syndrome. Clinical research suggests that compulsive-like symptoms are related to associative cortico-striatal dysfunctions, and tic-like symptoms to sensorimotor cortico-striatal dysfunctions. The knockout mouse (-KO), the current reference model to study such repetitive behaviours, presents both associative as well as sensorimotor cortico-striatal dysfunctions.

A simple and robust method for automating analysis of naïve and regenerating peripheral nerves.

Background: Manual axon histomorphometry (AH) is time- and resource-intensive, which has inspired many attempts at automation. However, there has been little investigation on implementation of automated programs for widespread use. Ideally such a program should be able to perform AH across imaging modalities and nerve states.

Sensitivity regularization of the Cramér-Rao lower bound to minimize B nonuniformity effects in quantitative magnetization transfer imaging.

Purpose: To develop and validate a regularization approach of optimizing B insensitivity of the quantitative magnetization transfer (qMT) pool-size ratio (F).

Methods: An expression describing the impact of B inaccuracies on qMT fitting parameters was derived using a sensitivity analysis. To simultaneously optimize for robustness against noise and B inaccuracies, the optimization condition was defined as the Cramér-Rao lower bound (CRLB) regularized by the B -sensitivity expression for the parameter of interest (F).

Promise and pitfalls of g-ratio estimation with MRI.

The fiber g-ratio is the ratio of the inner to the outer diameter of the myelin sheath of a myelinated axon. It has a limited dynamic range in healthy white matter, as it is optimized for speed of signal conduction, cellular energetics, and spatial constraints. In vivo imaging of the g-ratio in health and disease would greatly increase our knowledge of the nervous system and our ability to diagnose, monitor, and treat disease.

B -sensitivity analysis of quantitative magnetization transfer imaging.

Purpose: To evaluate the sensitivity of quantitative magnetization transfer (qMT) fitted parameters to B inaccuracies, focusing on the difference between two categories of T mapping techniques: B -independent and B -dependent.

Methods: The B -sensitivity of qMT was investigated and compared using two T measurement methods: inversion recovery (IR) (B -independent) and variable flip angle (VFA), B -dependent). The study was separated into four stages: 1) numerical simulations, 2) sensitivity analysis of the Z-spectra, 3) healthy subjects at 3T, and 4) comparison using three different B imaging techniques.

B mapping for bias-correction in quantitative T imaging of the brain at 3T using standard pulse sequences.

Purpose: B mapping is important for many quantitative imaging protocols, particularly those that include whole-brain T mapping using the variable flip angle (VFA) technique. However, B mapping sequences are not typically available on many magnetic resonance imaging (MRI) scanners. The aim of this work was to demonstrate that B mapping implemented using standard scanner product pulse sequences can produce B (and VFA T ) maps comparable in quality and acquisition time to advanced techniques.

Quantitative analysis of the myelin g-ratio from electron microscopy images of the macaque corpus callosum.

We provide a detailed morphometric analysis of eight transmission electron micrographs (TEMs) obtained from the corpus callosum of one cynomolgus macaque. The raw TEM images are included in the article, along with the distributions of the axon caliber and the myelin g-ratio in each image. The distributions are analyzed to determine the relationship between axon caliber and g-ratio, and compared against the aggregate metrics (myelin volume fraction, fiber volume fraction, and the aggregate g-ratio), as defined in the accompanying research article entitled 'In vivo histology of the myelin g-ratio with magnetic resonance imaging' (Stikov et al.

In vivo histology of the myelin g-ratio with magnetic resonance imaging.

The myelin g-ratio, defined as the ratio between the inner and the outer diameter of the myelin sheath, is a fundamental property of white matter that can be computed from a simple formula relating the myelin volume fraction to the fiber volume fraction or the axon volume fraction. In this paper, a unique combination of magnetization transfer, diffusion imaging and histology is presented, providing a novel method for in vivo magnetic resonance imaging of the axon volume fraction and the myelin g-ratio. Our method was demonstrated in the corpus callosum of one cynomolgus macaque, and applied to obtain full-brain g-ratio maps in one healthy human subject and one multiple sclerosis patient.

On the accuracy of T1 mapping: searching for common ground.

Purpose: There are many T1 mapping methods available, each of them validated in phantoms and reporting excellent agreement with literature. However, values in literature vary greatly, with T1 in white matter ranging from 690 to 1100 ms at 3 Tesla. This brings into question the accuracy of one of the most fundamental measurements in quantitative MRI.

Measurement of 129Xe gas apparent diffusion coefficient anisotropy in an elastase-instilled rat model of emphysema.

Hyperpolarized noble gas ((3)He and (129)Xe) apparent diffusion coefficient (ADC) measurements have shown remarkable sensitivity to microstructural (i.e., alveolar) changes in the lung, particularly emphysema.

Mapping of (3) He apparent diffusion coefficient anisotropy at sub-millisecond diffusion times in an elastase-instilled rat model of emphysema.

Hyperpolarized (3) He gas can provide detailed anatomical maps of the macroscopic airways in the lungs (i.e., ventilation) as well as insight into the lung microstructure through the apparent diffusion coefficient.

Cell cycle regulators in the neuronal death pathway of amyotrophic lateral sclerosis caused by mutant superoxide dismutase 1.

There is growing evidence for involvement of members of the cyclin-dependent kinase (Cdk) family in neurodegenerative disorders and in apoptotic death of neurons subjected to various insults. After our recent report that a deregulation of Cdk5 activity by p25 may contribute to pathogenesis of amyotrophic lateral sclerosis (ALS), we further examined the possible involvement of other Cdks in mice expressing a mutant form of superoxide dismutase (SOD1(G37R)) linked to ALS. No substantial changes in Cdk2 or Cdk6 distribution and kinase activities were detected in spinal motor neurons from SOD1(G37R) mice when compared with normal mice.

K252a and CEP1347 are neuroprotective compounds that inhibit mixed-lineage kinase-3 and induce activation of Akt and ERK.

K252a is best known as a Trk inhibitor, but is also a neuroprotective compound. CEP1347, a K252a derivative, retains neuroprotective properties, but does not inhibit TrkA. CEP1347 has recently been shown to directly inhibit MAPKKKs, including MLK3, but the effect of K252a on MAPKKKs remains unknown.