Considerations and recommendations from the ISMRM diffusion study group for preclinical diffusion MRI: Part 1: In vivo small-animal imaging.

Small-animal diffusion MRI (dMRI) has been used for methodological development and validation, characterizing the biological basis of diffusion phenomena, and comparative anatomy. The steps from animal setup and monitoring, to acquisition, analysis, and interpretation are complex, with many decisions that may ultimately affect what questions can be answered using the resultant data. This work aims to present selected considerations and recommendations from the diffusion community on best practices for preclinical dMRI of in vivo animals.

Considerations and recommendations from the ISMRM Diffusion Study Group for preclinical diffusion MRI: Part 3-Ex vivo imaging: Data processing, comparisons with microscopy, and tractography.

Preclinical diffusion MRI (dMRI) has proven value in methods development and validation, characterizing the biological basis of diffusion phenomena, and comparative anatomy. While dMRI enables in vivo non-invasive characterization of tissue, ex vivo dMRI is increasingly being used to probe tissue microstructure and brain connectivity. Ex vivo dMRI has several experimental advantages that facilitate high spatial resolution and high SNR images, cutting-edge diffusion contrasts, and direct comparison with histological data as a methodological validation.

Differentiating unirradiated mice from those exposed to conventional or FLASH radiotherapy using MRI.

Background And Purpose: The FLASH effect expands the therapeutic ratio of tumor control to normal tissue toxicity observed after delivery of ultra-high (>100 Gy/s FLASH-RT) vs. conventional dose rate radiation (CONV-RT). In this first exploratory study, we assessed whether ex-vivo Magnetic Resonance Imaging (MRI) could reveal long-term differences after FLASH-RT and CONV-RT whole-brain irradiation.

Sex differences in the association of Alzheimer's disease biomarkers and cognition in a multicenter memory clinic study.

Background: This study investigated sex differences in the associations between Alzheimer's disease (AD) biomarkers, cognitive performance, and decline in memory clinic settings.

Methods: 249 participants (females/males:123/126), who underwent tau-PET, amyloid-PET, structural MRI, and plasma glial fibrillary acidic protein (GFAP) measurement were included from Geneva and Lausanne Memory Clinics. Mann-Whitney U tests investigated sex differences in clinical and biomarker data.

Brain and plasmatic CLUSTERIN are translational markers of Alzheimer's disease.

Early diagnosis of late-onset Alzheimer's disease (AD) by peripheral biomarkers remains a challenge; many have been proposed, but none have been evaluated in a prospective manner. CLUSTERIN (CLU), a chaperone protein expressed in the brain and found in relatively high concentrations in plasma, is a promising candidate. CLU contributes to the elimination of β-amyloid (Aβ), which is associated to neurofibrillary tangles and to the genetic risk for AD.

synMARSS-An End-To-End Platform for the Parametric Generation of Synthetic In Vivo Magnetic Resonance Spectra.

Synthetic magnetic resonance spectra (MRS) are mathematically generated spectra which can be used to investigate the assumptions of data analysis strategies, optimize experimental design, and as training data for the development and validation of machine learning tools. In this work, we extend Magnetic Resonance Spectrum Simulator (MARSS), a popular MRS basis set simulation tool, to be able to generate synthetic spectra for an arbitrary MRS sequence. The extension, referred to as synMARSS, converts a basis set as well as a set of NMR, tissue-related and additional sequence parameters into high-quality synthetic spectra via a parametric model.

Unraveling the link between frailty and Alzheimer's disease biomarkers in patients with mild cognitive impairment.

Alzheimer's disease (AD) can be identified through biomarkers of amyloid (A) and tau (T) pathology. Frailty, a measure of biological aging, could impact the association between AD neuropathology and its clinical manifestation. We aimed to investigate the relationship between frailty and AD biomarkers among people with mild cognitive impairment (MCI) attending a university memory clinic.

Three-Objects-Three-Places Episodic Memory Test to Screen Mild Cognitive Impairment and Mild Dementia: Validation in a Memory Clinic Population.

Background: The Three-Objects-Three-Places (3O3P) test is a 5-min screen for episodic memory impairment due to Alzheimer's disease, known for its briefness and easy administration, culture- and language-free nature, and the absence of specific equipment. However, no studies have validated its potential in memory clinic cohorts. The aim of this study was to test its convergent, discriminant, and known-group validities and to define thresholds for its clinical use.

Early metabolic changes in the brain of Alzheimer's disease rats are driven by GLAST+ cells.

Glucose metabolic dysfunction is a hallmark of Alzheimer's disease (AD) pathology and is used to diagnose the disease or predict imminent cognitive decline. The main method to measure brain metabolism is positron emission tomography with 2-Deoxy-2-[F]fluoroglucose ([F]FDG-PET). The cellular origin of changes in the [F]FDG-PET signal in AD is controversial.

How does Independent Component Analysis Preprocessing Affect EEG Microstates?

Over recent years, electroencephalographic (EEG) microstates have been increasingly used to investigate, at a millisecond scale, the temporal dynamics of large-scale brain networks. By studying their topography and chronological sequence, microstates research has contributed to the understanding of the brain's functional organization at rest and its alteration in neurological or mental disorders. Artifact removal strategies, which differ from study to study, may alter microstates topographies and features, possibly reducing the generalizability and comparability of results across research groups.

Characterization of language abilities and semantic networks in very preterm children at school-age.

It has been widely assessed that very preterm children (<32 weeks gestational age) present language and memory impairments compared with full-term children. However, differences in their underlying semantic memory structure have not been studied yet. Nevertheless, the way concepts are learned and organized across development relates to children's capacities in retrieving and using information later.

Early-phase F-Flortaucipir tau-PET as a proxy of brain metabolism in Alzheimer's disease: a comparison with F-FDG-PET and early-phase amyloid-PET.

Purpose: As dual-phase amyloid-PET can evaluate amyloid (A) and neurodegeneration (N) with a single tracer injection, dual-phase tau-PET might be able to provide both tau (T) and N. Our study aims to assess the association of early-phase tau-PET scans and F-fluorodeoxyglucose (FDG) PET and their comparability in discriminating Alzheimer's disease (AD) patients and differentiating neurodegenerative patterns.

Methods: 58 subjects evaluated at the Geneva Memory Center underwent dual-phase F-Flortaucipir-PET with early-phase acquisition (eTAU) and F-FDG-PET within 1 year.

Connectome embedding in multidimensional graph spaces.

Connectomes' topological organization can be quantified using graph theory. Here, we investigated brain networks in higher dimensional spaces defined by up to 10 graph theoretic nodal properties. These properties assign a score to nodes, reflecting their meaning in the network.

Improved phosphorus MRSI acquisition through compressed sensing acceleration combined with low-rank reconstruction.

Objectives: Phosphorus-31 magnetic resonance spectroscopic imaging (P-MRSI) is a non-invasive tool for assessing cellular high-energy metabolism in-vivo. However, its acquisition suffers from a low sensitivity, which necessitates large voxel sizes or multiple averages to achieve an acceptable signal-to-noise ratio (SNR), resulting in long scan times.

Materials And Methods: To overcome these limitations, we propose an acquisition and reconstruction scheme for FID-MRSI sequences.

Fast High-Resolution Metabolite Mapping in the rat Brain Using H-FID-MRSI at 14.1 T.

Magnetic resonance spectroscopic imaging (MRSI) enables the simultaneous noninvasive acquisition of MR spectra from multiple spatial locations inside the brain. Although H-MRSI is increasingly used in the human brain, it is not yet widely applied in the preclinical setting, mostly because of difficulties specifically related to very small nominal voxel size in the rat brain and low concentration of brain metabolites, resulting in low signal-to-noise ratio (SNR). In this context, we implemented a free induction decay H-MRSI sequence (H-FID-MRSI) in the rat brain at 14.

Acquisition of musical skills and abilities in older adults-results of 12 months of music training.

Background: Older adults can acquire new skills across different domains. Practicing a musical instrument has been identified as a promising activity for improving cognition, promoting well-being, and inducing brain plasticity in older individuals. However, the mechanisms of these changes are still poorly understood.

ECCENTRIC: A fast and unrestrained approach for high-resolution in vivo metabolic imaging at ultra-high field MR.

A novel method for fast and high-resolution metabolic imaging, called ECcentric Circle ENcoding TRajectorIes for Compressed sensing (ECCENTRIC), has been developed at 7 Tesla MRI. ECCENTRIC is a non-Cartesian spatial-spectral encoding method designed to accelerate magnetic resonance spectroscopic imaging (MRSI) with high signal-to-noise at ultra-high field. The approach provides flexible and random sampling of the Fourier space without temporal interleaving to improve spatial response function and spectral quality.

Improved myocardial scar visualization using free-breathing motion-corrected wideband black-blood late gadolinium enhancement imaging in patients with implantable cardiac devices.

Purpose: The purpose of this study was to introduce and evaluate a novel 2D wideband black-blood (BB) LGE sequence, incorporating wideband inversion recovery, wideband T2 preparation, and non-rigid motion correction (MOCO) reconstruction, to improve myocardial scar detection and address artifacts associated with implantable cardioverter defibrillators (ICDs).

Materials And Methods: The wideband MOCO free-breathing BB-LGE sequence was tested on a sheep with ischemic scar and in 22 patients with cardiac disease, including 15 with cardiac implants, at 1.5T.

A flexible framework for the design and optimization of water-excitation RF pulses using B-spline interpolation.

Purpose: To implement a flexible framework, named HydrOptiFrame, for the design and optimization of time-efficient water-excitation (WE) RF pulses using B-spline interpolation, and to characterize their lipid suppression performance.

Methods: An evolutionary optimization algorithm was used to design WE RF pulses. The algorithm minimizes a composite loss function that quantifies the fat-water contrast using Bloch equation simulations.

Effects of cholestasis and hyperammonemia on dendritic spine density and turnover in rat hippocampal neurons.

Adults and children with cholestatic liver disease are at risk for type C hepatic encephalopathy (HE) and may present lifelong neurocognitive impairment. While the underlying cellular and molecular mechanisms are still incompletely understood, ammonium and bile acids (BAs) seem to play a key role in this pathology, by crossing the blood-brain-barrier and modifying neuronal homeostasis and synaptic plasticity. This experimental study aimed to investigate the effects of ammonium and BAs on dendritic spines of rat hippocampal CA1 neurons.

Susceptibility-induced internal gradients reveal axon morphology and cause anisotropic effects in the diffusion-weighted MRI signal.

Diffusion-weighted MRI is our most promising method for estimating microscopic tissue morphology in vivo. The signal acquisition is based on scanner-generated external magnetic gradients. However, it will also be affected by susceptibility-induced internal magnetic gradients caused by interactions between the tissue and the static magnetic field of the scanner.

Comparing structure-function relationships in brain networks using EEG and fNIRS.

Identifying relationships between structural and functional networks is crucial for understanding the large-scale organization of the human brain. The potential contribution of emerging techniques like functional near-infrared spectroscopy to investigate the structure-functional relationship has yet to be explored. In our study, using simultaneous Electroencephalography (EEG) and Functional near-infrared spectroscopy (fNIRS) recordings from 18 subjects, we characterize global and local structure-function coupling using source-reconstructed EEG and fNIRS signals in both resting state and motor imagery tasks, as this relationship during task periods remains underexplored.

Centiloid recommendations for clinical context-of-use from the AMYPAD consortium.

Amyloid-PET quantification through the tracer-independent Centiloid (CL) scale has emerged as an essential tool for the accurate measurement of amyloid-β (Aβ) pathology in Alzheimer's disease (AD) patients. The AMYPAD consortium set out to integrate existing literature and recent work from the consortium to provide clinical context-of-use recommendations for the CL scale. Compared to histopathology, visual reads, and cerebrospinal fluid, CL quantification accurately reflects the amount of AD pathology.

3D Creatine Kinase Imaging (CKI) for In Vivo Whole-Brain Mapping of Creatine Kinase Reaction Rates with P-Magnetization Transfer MR Fingerprinting.

The creatine kinase (CK) is a key enzyme involved in brain bioenergetics, playing a key role in brain function and the pathogenesis of neurological and psychiatric diseases, but imaging its activity noninvasively in the human brain in vivo remains a significant challenge. This study aims to advance the magnetization transfer (MT)- P magnetic resonance fingerprinting (MRF) for 3D Creatine Kinase Imaging (CKI). The method was implemented and validated on a clinical 7 Tesla MRI scanner.