Central Vein Sign and Paramagnetic Rim Lesions: Susceptibility Changes in Brain Tissues and Their Implications for the Study of Multiple Sclerosis Pathology.

Multiple sclerosis (MS) is the most common acquired inflammatory and demyelinating disease in adults. The conventional diagnostic of MS and the follow-up of inflammatory activity is based on the detection of hyperintense foci in T2 and fluid-attenuated inversion recovery (FLAIR) magnetic resonance imaging (MRI) and lesions with brain-blood barrier (BBB) disruption in the central nervous system (CNS) parenchyma. However, T2/FLAIR hyperintense lesions are not specific to MS and the MS pathology and inflammatory processes go far beyond focal lesions and can be independent of BBB disruption. MRI techniques based on the magnetic susceptibility properties of the tissue, such as T2*, susceptibility-weighted images (SWI), and quantitative susceptibility mapping (QSM) offer tools for advanced MS diagnostic, follow-up, and the assessment of more detailed features of MS dynamic pathology. Susceptibility-weighted techniques are sensitive to the paramagnetic components of biological tissues, such as deoxyhemoglobin. This capability enables the visualization of brain parenchymal veins. Consequently, it presents an opportunity to identify veins within the core of multiple sclerosis (MS) lesions, thereby affirming their venocentric characteristics. This advancement significantly enhances the accuracy of the differential diagnostic process. Another important paramagnetic component in biological tissues is iron. In MS, the dynamic trafficking of iron between different cells, such as oligodendrocytes, astrocytes, and microglia, enables the study of different stages of demyelination and remyelination. Furthermore, the accumulation of iron in activated microglia serves as an indicator of latent inflammatory activity in chronic MS lesions, termed paramagnetic rim lesions (PRLs). PRLs have been correlated with disease progression and degenerative processes, underscoring their significance in MS pathology. This review will elucidate the underlying physical principles of magnetic susceptibility and their implications for the formation and interpretation of T2*, SWI, and QSM sequences. Additionally, it will explore their applications in multiple sclerosis (MS), particularly in detecting the central vein sign (CVS) and PRLs, and assessing iron metabolism. Furthermore, the review will discuss their role in advancing early and precise MS diagnosis and prognostic evaluation, as well as their utility in studying chronic active inflammation and degenerative processes.

Left-sided epileptiform activity influences language lateralization in right mesial temporal sclerosis.

OBJECTIVE: To investigate the association between left epileptiform activity and language laterality indices (LI) in patients with right mesial temporal sclerosis (MTS). METHODS: Twenty-two patients with right MTS and 22 healthy subjects underwent fMRI scanning while performing a language task. LI was calculated in multiple regions of interest (ROI). Data on the presence of left epileptiform abnormalities were obtained during prolonged video-EEG monitoring. RESULTS: After correction for multiple comparisons, LI was reduced in the middle temporal gyrus in the left interictal epileptiform discharges (IED+) group, compared with the left IED- group (p < 0.05). SIGNIFICANCE: Using a responsive reading naming fMRI paradigm, right MTS patients who presented left temporal interictal epileptiform abnormalities on video-EEG showed decreased LI in the middle temporal gyrus, indicating decreased left middle temporal gyrus activation, increased right middle temporal gyrus activation or a combination of both, demonstrative of language network reorganization, specially in the MTG, in this patient population. PLAIN LANGUAGE SUMMARY: This research studied 22 patients with right mesial temporal sclerosis (a specific type of epilepsy) comparing them to 22 healthy individuals. Participants were asked to perform a language task while undergoing a special brain imaging technique (fMRI). The findings showed that patients with epilepsy displayed a change in the area of the brain typically responsible for language processing. This suggests that their brains may have adapted due to their condition, altering the way language is processed.

Novel Gadolinium-Free Ultrasmall Nanostructured Positive Contrast for Magnetic Resonance Angiography and Imaging.

Nanostructured contrast agents are promising alternatives to Gd3+-based chelates in magnetic resonance (MR) imaging techniques. A novel ultrasmall paramagnetic nanoparticle (UPN) was strategically designed to maximize the number of exposed paramagnetic sites and r1 while minimizing r2, by decorating 3 nm titanium dioxide nanoparticles with suitable amounts of iron oxide. Its relaxometric parameters are comparable to those of gadoteric acid (GA) in agar phantoms, and the r2/r1 ratio of 1.38 at 3 T is close to the ideal unitary value. The strong and prolonged contrast enhancement of UPN before renal excretion was confirmed by T1-weighted MR images of Wistar rats after intravenous bolus injection. Those results associated with good biocompatibility indicate its high potential as an alternative blood-pool contrast agent to the GA gold standard for MR angiography, especially for patients with severe renal impairment.

Evaluation of multi-channel phase reconstruction methods for quantitative susceptibility mapping on postmortem human brain.

Quantitative Susceptibility Mapping (QSM) is an established Magnetic Resonance Imaging (MRI) technique with high potential in brain iron studies associated to several neurodegenerative diseases. Unlike other MRI techniques, QSM relies on phase images to estimate tissue's relative susceptibility, therefore requiring a reliable phase data. Phase images from a multi-channel acquisition should be reconstructed in a proper way. On this work it was compared the performance of combination of phase matching algorithms (MCPC3D-S and VRC) and phase combination methods based on a complex weighted sum of phases, considering the magnitude at different powers (k = 0 to 4) as the weighting factor. These reconstruction methods were applied in two datasets: a simulated brain dataset for a 4-coil array and data of 22 postmortem subjects acquired at a 7T scanner using a 32 channels coil. For the simulated dataset, differences between the ground truth and the Root Mean Squared Error (RMSE) were evaluated. For both simulated and postmortem data, the mean (MS) and standard deviation (SD) of susceptibility values of five deep gray matter regions were calculated. For the postmortem subjects, MS and SD were statistically compared across all subjects. A qualitative analysis indicated no differences between methods, except for the Adaptive approach on postmortem data, which showed intense artifacts. In the 20% noise level case, the simulated data showed increased noise in central regions. Quantitative analysis showed that both MS and SD were not statistically different when comparing k = 1 and k = 2 on postmortem brain images, however visual inspection showed some boundaries artifacts on k = 2. Furthermore, the RMSE decreased (on regions near the coils) and increased (on central regions and on overall QSM) with increasing k. In conclusion, for reconstruction of phase images from multiple coils with no reference available, alternative methods are needed. In this study it was found that overall, the phase combination with k = 1 is preferred over other powers of k.

Decompose quantitative susceptibility mapping (QSM) to sub-voxel diamagnetic and paramagnetic components based on gradient-echo MRI data.

PURPOSE: A method named DECOMPOSE-QSM is developed to decompose bulk susceptibility measured with QSM into sub-voxel paramagnetic and diamagnetic components based on a three-pool complex signal model. METHODS: Multi-echo gradient echo signal is modeled as a summation of three weighted exponentials corresponding to three types of susceptibility sources: reference susceptibility, diamagnetic and paramagnetic susceptibility relative to the reference. Paramagnetic component susceptibility (PCS) and diamagnetic component susceptibility (DCS) maps are constructed to represent the sub-voxel compartments by solving for linear and nonlinear parameters in the model. RESULTS: Numerical forward simulation and phantom validation confirmed the ability of DECOMPOSE-QSM to separate the mixture of paramagnetic and diamagnetic components. The PCS obtained from temperature-variant brainstem imaging follows the Curie's Law, which further validated the model and the solver. Initial in vivo investigation of human brain images showed the ability to extract sub-voxel PCS and DCS sources that produce visually enhanced contrast between brain structures comparing to threshold QSM.

Effects of a 7-Day Meditation Retreat on the Brain Function of Meditators and Non-Meditators During an Attention Task.

Meditation as a cognitive enhancement technique is of growing interest in the field of health and research on brain function. The Stroop Word-Color Task (SWCT) has been adapted for neuroimaging studies as an interesting paradigm for the understanding of cognitive control mechanisms. Performance in the SWCT requires both attention and impulse control, which is trained in meditation practices. We presented SWCT inside the MRI equipment to measure the performance of meditators compared with non-meditators before and after a meditation retreat. The aim of this study was to evaluate the effects of a 7-day Zen intensive meditation training (a retreat) on meditators and non-meditators in this task on performance level and neural mechanisms. Nineteen meditators and 14 non-meditators were scanned before and after a 7-day Zen meditation retreat. No significant differences were found between meditators and non-meditators in the number of the correct responses and response time (RT) during SWCT before and after the retreat. Probably, due to meditators training in attention, their brain activity in the contrast incongruent > neutral during the SWCT in the anterior cingulate, ventromedial prefrontal cortex/anterior cingulate, caudate/putamen/pallidum/temporal lobe (center), insula/putamen/temporal lobe (right) and posterior cingulate before the retreat, were reduced compared with non-meditators. After the meditation retreat, non-meditators had reduced activation in these regions, becoming similar to meditators before the retreat. This result could be interpreted as an increase in the brain efficiency of non-meditators (less brain activation in attention-related regions and same behavioral response) promoted by their intensive training in meditation in only 7 days. On the other hand, meditators showed an increase in brain activation in these regions after the same training. Intensive meditation training (retreat) presented distinct effects on the attention-related regions in meditators and non-meditators probably due to differences in expertise, attention processing as well as neuroplasticity.

Interictal abnormal fMRI activation of visual areas during a motor task cued by visual stimuli in migraine.

OBJECTIVE: To assess changes in blood-oxygen-level-dependent activity after light deprivation compared to regular light exposure in subjects with migraine in the interictal state and in controls. METHODS: Ten subjects with migraine and ten controls participated in two sessions of functional magnetic resonance imaging. In each session, they performed a finger-tapping task with the right hand, cued by visual stimuli. They were scanned before and after 30 minutes of light deprivation or light exposure. In subjects with migraine, functional magnetic resonance imaging was performed interictally. Analysis of variance was made with the factors time (before or after), session (light deprivation or exposure), and group (migraine or control). RESULTS: There were significant "group" effects in a cluster in the bilateral cuneus encompassing the superior border of the calcarine sulcus and extrastriate cortex. There were no significant effects of "time", "session", or interactions between these factors. CONCLUSION: The main result of this study is consistent with aberrant interictal processing of visual information in migraine. Light deprivation did not modulate functional magnetic resonance imaging activity in subjects with or without migraine. OBJETIVO: Avaliar mudanças na atividade cerebral por meio de ressonância magnética funcional após privação luminosa comparada à exposição à luz, em indivíduos com enxaqueca no estado interictal e em controles. MÉTODOS: Dez indivíduos com enxaqueca e dez controles participaram de duas sessões de ressonância magnética funcional. Em cada sessão, realizaram uma tarefa motora com a mão direita guiada por estímulos visuais. Foram colhidas imagens antes e após 30 minutos de privação luminosa ou exposição à luz. Em indivíduos com enxaqueca, a ressonância funcional foi realizada no período interictal. Foi feita a análise de variância com fatores tempo (antes ou depois), sessão (privação ou exposição à luz) e grupo (enxaqueca ou controle). RESULTADOS: Houve efeitos significativos de "grupo" em uma área no cúneo bilateral, incluindo a borda superior do sulco calcarino e o córtex extraestriado. Não houve efeitos significativos de "tempo", "sessão" ou interações entre estes fatores. CONCLUSÃO: O principal resultado deste estudo sugere um processamento interictal anormal das informações visuais em indivíduos com enxaqueca. A privação luminosa não modulou a atividade na ressonância magnética funcional em indivíduos com ou sem enxaqueca.

Interictal abnormal fMRI activation of visual areas during a motor task cued by visual stimuli in migraine / Ativação interictal anormal de áreas visuais por ressonância magnética funcional durante uma tarefa visuo-motora em indivíduos com enxaqueca

ABSTRACT Objective To assess changes in blood-oxygen-level-dependent activity after light deprivation compared to regular light exposure in subjects with migraine in the interictal state and in controls. Methods Ten subjects with migraine and ten controls participated in two sessions of functional magnetic resonance imaging. In each session, they performed a finger-tapping task with the right hand, cued by visual stimuli. They were scanned before and after 30 minutes of light deprivation or light exposure. In subjects with migraine, functional magnetic resonance imaging was performed interictally. Analysis of variance was made with the factors time (before or after), session (light deprivation or exposure), and group (migraine or control). Results There were significant “group” effects in a cluster in the bilateral cuneus encompassing the superior border of the calcarine sulcus and extrastriate cortex. There were no significant effects of “time”, “session”, or interactions between these factors. Conclusion The main result of this study is consistent with aberrant interictal processing of visual information in migraine. Light deprivation did not modulate functional magnetic resonance imaging activity in subjects with or without migraine.

RESUMO Objetivo Avaliar mudanças na atividade cerebral por meio de ressonância magnética funcional após privação luminosa comparada à exposição à luz, em indivíduos com enxaqueca no estado interictal e em controles. Métodos Dez indivíduos com enxaqueca e dez controles participaram de duas sessões de ressonância magnética funcional. Em cada sessão, realizaram uma tarefa motora com a mão direita guiada por estímulos visuais. Foram colhidas imagens antes e após 30 minutos de privação luminosa ou exposição à luz. Em indivíduos com enxaqueca, a ressonância funcional foi realizada no período interictal. Foi feita a análise de variância com fatores tempo (antes ou depois), sessão (privação ou exposição à luz) e grupo (enxaqueca ou controle). Resultados Houve efeitos significativos de “grupo” em uma área no cúneo bilateral, incluindo a borda superior do sulco calcarino e o córtex extraestriado. Não houve efeitos significativos de “tempo”, “sessão” ou interações entre estes fatores. Conclusão O principal resultado deste estudo sugere um processamento interictal anormal das informações visuais em indivíduos com enxaqueca. A privação luminosa não modulou a atividade na ressonância magnética funcional em indivíduos com ou sem enxaqueca.

X-PloRat: A Software for Scoring Animal Behavior in Enclosed Spaces / X-PloRat: Software para o Registro do Comportamento em Espaços Confinados

ABSTRACT The present technical note introduces the X-PloRat, a software for the scoring of animal location, displacement, and other behavioral properties, in enclosed spaces. The X-PloRat offers a variety of data reports and can be used for training students in behavioral observation and in validating other kinds of scoring procedures.

RESUMO A presente nota técnica apresenta o X-PloRat, um software que permite o registro da localização, deslocamento e outras propriedades do comportamento animal em espaços confinados. O X-PloRat oferece uma grande variedade de relatórios e pode ajudar no treinamento de estudantes em observação do comportamento e também na validação de outros tipos de registros.