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Objective: Phase contrast sequence may be used to measure the flux of blood in vessels. The result might be, however, corrupted by many errors including partial volume effect (PVE), region of interest (ROI) contouring, and noise. In this study we aim to quantify the error and if possible to suggest a proper strategy to minimize it. Methods: Water flux was measured using a plastic flow phantom and changing the flow rate and spatial resolution which affects the PVE error. Signal-to-noise ratio (SNR) of magnitude images was used to estimate error caused by noise and a comparison to a statistical error from several measurements was made. Water flux in vitro and flux through aortal valve and sinotubular junction in vivo was also measured with undersized and oversized ROIs. Results: The PVE subsides as spatial resolution improves and as the difference between magnitude signal from flowing and static tissue decreases. The error of flow through aortal valve was estimated to be 0.45%. Noise affects random error (estimation 0.05%) less then flow fluctuations (0.25%). The ROI size underestimation may lead to a severe underestimation of flow (over 10%) and a small underestimation in the case of aortal valve flow to a mild overestimation (5%). In general, an overestimation of ROI size is also erroneous (6%), although not as severe as underestimation. Conclusion: The most relevant source of error out of the three sources examined is ROI contouring with overestimation being recommended over underestimation. The error resulting from the PVE is small compared to ROI contouring error. The error caused by noise is negligible compared to flow fluctuation. [ABSTRACT FROM AUTHOR]

This article contributes to 30. years anniversary of the first installation of the very first Czechoslovak magnetic resonance system (MR). It makes an effort to map some important local and global mile stones over three decade's long exciting way of clinical and scientific application of this amazing method. Albeit the contribution has not typical educative character it explains some basic physical relations which considerably formed the effort and the development of all parts of MR system. Therefore also this article is structured to cover the development of all MR components in historical context. But not to staying only in history the next important aspect is to bring a survey about today's modern capabilities of MR systems as well as to introduce new perspectives for future years. [ABSTRACT FROM AUTHOR]

Functional MR imaging (fMRI) belongs already longer than two decades between methods used for the investigation of the human brain but also for monitoring of functional changes related to pathological processes. This article shortly explains physical and physiological basis of fMRI methods and shows its advantages and limitations. Also, various types of fMRI data acquisition and evaluation are discussed including their benefits as well as restrictions. Using several examples, different approach to fMRI application is demonstrated beginning with traditional visualization of activated regions to more modern way of investigation of the brain network connectivity. This article is not a survey of published results in fMRI field but rather it should help to reader with orientation in entire issues concerning of fMRI including some new trends in this region. [ABSTRACT FROM AUTHOR]

MR tractography (MRT) has become an important method for noninvasive visualization of white matter bundles and peripheral nerves using magnetic resonance imaging measurment of water molecule diffusion. This paper gives a short historical overview and implementation of the MRT into clinical practice in the institute IKEM. Furthermore, the paper gives a short overview of some MRT applications of brain and 3D MR neurography of peripheral nerves. The MR tractography and MR neurography may be used in the presurgical planning and post- -operative follow-up of the brain and peripheral nerves microstructural changes. [ABSTRACT FROM AUTHOR]

Hearing loss, presbycusis, is one of the most common sensory declines in the ageing population. Presbycusis is characterised by a deterioration in the processing of temporal sound features as well as a decline in speech perception, thus indicating a possible central component. With the aim to explore the central component of presbycusis, we studied the function of the auditory cortex by functional MRI in two groups of elderly subjects (>65 years) and compared the results with young subjects (

The study is designed to determine the relationship between the progress of the wet form of age-related macular degeneration and the activity of the visual cortex examined using functional magnetic resonance imaging. Ten patients with the wet form of age-related macular degeneration (9 female and 1 male) with a mean age of 74.7 years (58-85 years) at various stages of bilateral involvement of the disease were included. Patients did not suffer from any other ocular nor neurological disease. All the patients underwent functional magnetic resonance imaging examinations with stimulation of both eyes using a black-and-white checkerboard of size 25.8 × 16.2 degrees. The group was compared with a group of healthy subjects with an average age of 54.1 years (45-65 years). For statistical evaluation, the Mann-Whitney U test was used. Comparing the extent of visual cortex activations we found a statistically significant difference between both the groups ( p = 0.0247). However, the dependence of functional magnetic resonance imaging activity on visual acuity was not statistically significant ( p = 0.223). We conclude that in patients with the wet form of age-related macular degeneration, lower functional magnetic resonance imaging activity of the visual cortex was found compared with the control group of healthy subjects. Dependence of functional magnetic resonance imaging activity on visual acuity was not statistically significant. [ABSTRACT FROM AUTHOR]

One of the recognised complications of catheter ablation is pulmonary venous stenosis. The aim of this study was to compare two methods of evaluation of pulmonary venous diameter for follow-up assessment of the above complication: (1) a linear approach evaluating two main diameters of the vein, (2) semiautomatically measured cross-sectional area (CSA). The study population consists of 29 patients. All subjects underwent contrast-enhanced magnetic resonance angiography (CeMRA) of the pulmonary veins (PVs) before and after the ablation; 14 patients were also scanned 3 months later. PV diameter was evaluated from two-dimensional multiplanar reconstructions by measuring either the linear diameter or CSA. A comparison between pulmonary venous CSA and linear measurements revealed a systematic difference in absolute values. This difference was not significant when comparing the relative change CSA and quadratic approximation using linear extents (linear approach). However, a trend towards over-estimation of calibre reduction was documented for the linear approach. Using CSA assessment, significant PV stenosis was found in ten PVs (8%) shortly after ablation. Less significant PV stenosis, ranging from 20 to 50% was documented in other 18 PVs (15%). CeMRA with CSA assessment of the PVs is suitable method for evaluation of PV diameters. [ABSTRACT FROM AUTHOR]

Introduction: Catheter ablation of atrial fibrillation (AF) requires exact anatomical information about pulmonary venous (PV) ostia. In this study, anatomy of pulmonary veins (PVs) was assessed using three-dimensional (3D) reconstructions of magnetic resonance angiography (MRA). Methods and Results: Contrast-enhanced MRA of the PVs was performed in 40 patients (mean age 53 ± 9 years) with paroxysmal (30 patients) or persistent (10 patients) AF, scheduled for circumferential ablation around PV ostia. PV ostial anatomy and diameters were evaluated from multiplanar reconstructions and compared with 3D reconstructions. Thirty (75%) patients presented with a common left-sided antrum (21 short and 9 long trunk), while additional PVs were found on right side in 23%. PV ostia were oblong in shape (mean diameters 17.0 ± 4.3 vs 10.5 ± 2.5 mm by two-dimensional (2D) measurements, and 20.8 ± 7.6 mm vs 12.9 ± 3.3 mm by 3D reconstruction, in long and short axis, respectively). There was a correlation between measurements obtained from 2D and 3D images, although 3D imaging provided slightly larger diameters. Conclusions: MRA with 3D reconstructions is an important technique for preprocedural assessment of PVs that allows full understanding of their anatomy and size. This information may be important for selection of appropriate tools. [ABSTRACT FROM AUTHOR]

Background and purpose Methods Results Conclusions Cognitive impairment (CI) in multiple sclerosis (MS) is associated with bidirectional changes in resting‐state centrality measures. However, practicable functional magnetic resonance imaging (fMRI) biomarkers of CI are still lacking. The aim of this study was to assess the graph‐theory‐based degree rank order disruption index (kD) and its association with cognitive processing speed as a marker of CI in patients with MS (PwMS) in a secondary cross‐sectional fMRI analysis.Differentiation between PwMS and healthy controls (HCs) using kD and its correlation with CI (Symbol Digit Modalities Test) was compared to established imaging biomarkers (regional degree, volumetry, diffusion‐weighted imaging, lesion mapping). Additional associations were assessed for fatigue (Fatigue Scale for Motor and Cognitive Functions), gait and global disability.Analysis in 56 PwMS and 58 HCs (35/27 women, median age 45.1/40.5 years) showed lower kD in PwMS than in HCs (median −0.30/−0.06, interquartile range 0.55/0.54; p = 0.009, Mann–Whitney U test), yielding acceptable yet non‐superior differentiation (area under curve 0.64). kD and degree in medial prefrontal cortex (MPFC) correlated with CI (kD/MPFC Spearman's ρ = 0.32/−0.45, p = 0.019/0.001, n = 55). kD also explained fatigue (ρ = −0.34, p = 0.010, n = 56) but neither gait nor disability.kD is a potential biomarker of CI and fatigue warranting further validation. [ABSTRACT FROM AUTHOR]

Aim: The aim of the article is to qualitatively assess the usability of a mathematical flow model for visualizing the flow in aortic bifurcation treated with stents. Methodology: Nine examinations of aortic bifurcations were conducted using a 4D Flow sequence. Patients without stents, patients with a stent in one branch, and patients with stents in both branches of the aortic bifurcation were examined. 4D Flow data were used to prepare a visualization of the velocity field. Flow simulations were performed based on the segmented bifurcation and measured flow data, including areas where flow measurements were affected by artifacts. Measured and simulated velocity fields were visually compared. Results: For patients without stents, the simulated flow contributed to eliminating small inaccuracies in the measured field. In patients with stents, the simulated data were more consistent than the measured data and provided additional insight into the situation within the stents. Discussion: Simulated velocity fields must inherently adhere to the laws of physics, allowing for the correction of measured data in regions where measurements are compromised. Depending on the accuracy of the segmentation, it may also offer new diagnostic information. However, the obtained results are solely qualitative and will need quantitative validation. Conclusion: The mathematical flow model can aid in quantitative assessment of flow in the vascular locations treated with stents where the direct MR measurement of blood flow fails. [ABSTRACT FROM AUTHOR]

The volume reduction of the gray matter structures in patients with Alzheimer's disease is often accompanied by an asymmetric increase in the number of white matter fibers located close to these structures. The present study aims to investigate the white matter structure changes in the motor basal ganglia in Alzheimer's disease patients compared to healthy controls using diffusion tensor imaging. The amounts of tracts, tract length, tract volume, quantitative anisotropy, and general fractional anisotropy were measured in ten patients with Alzheimer's disease and ten healthy controls. A significant decrease in the number of tracts and general fractional anisotropy was found in patients with Alzheimer's disease compared to controls in the right caudate nucleus, while an increase was found in the left and the right putamen. Further, a significant decrease in the structural volume of the left and the right putamen was observed. An increase in the white matter diffusion tensor imaging parameters in patients with Alzheimer's disease was observed only in the putamen bilaterally. The right caudate showed a decrease in both the diffusion tensor imaging parameters and the volume in Alzheimer's disease patients. The right pallidum showed an increase in the diffusion tensor imaging parameters but a decrease in volume in Alzheimer's disease patients. [ABSTRACT FROM AUTHOR]

The necessity of using non-Newtonian models for hemodynamics in geometries mimicking large vessels is investigated. Phase-contrast magnetic resonance imaging (PC-MRI) measurements are performed on a specially-designed phantom representing the aorta while using several types of fluids. These measurements are compared against the results of the lattice Boltzmann method (LBM) computational fluid dynamics (CFD) simulator in 3D. On the phantom side, two types of non-Newtonian fluids (water-based solutions of glycerine with xanthan gum and sucrose with xanthan gum) and Newtonian fluid (clear water) are used in the experiments; three different acrylic plates are inserted to represent aortic stenosis of varying degrees; and two constant flow regimes with high and low flow rates are used. The CFD simulations in the geometry and inflow boundary conditions corresponding to each experiment are performed both with non-Newtonian and Newtonian approaches. Additionally, the accuracy of the PC-MRI flow measurements is assessed and discussed with respect to the known PC-MRI flow underestimation due to turbulence. Based on the type of stenosis and inflow rate, the results indicate that the Newtonian models produce comparable results with the experimentally acquired data, which is in favor of overall less expensive Newtonian models. [ABSTRACT FROM AUTHOR]

The goal of this paper is to inform about the 4D Flow sequence, its advantages and disadvantages. 4D Flow examination allows to assess flow rate and other flow parameters in the volume of interest retrospectively. However, it is expensive in terms of time and postprocessing. An in-house software may be necessary, as commercial programs remain costly. They offer a number of functionalities and data corrections. Their segmentations tools, however, remain relatively limited. Low spatial resolution and long data acquisition are the primary limitations of the sequence. [ABSTRACT FROM AUTHOR]

Functional connectivity analysis is a common approach to the characterization of brain function. While studies of functional connectivity have predominantly focused on resting‐state fMRI, naturalistic paradigms, such as movie watching, are increasingly being used. This ecologically valid, yet relatively unconstrained acquisition state has been shown to improve subject compliance and, potentially, enhance individual differences. However, unlike the reliability of resting‐state functional connectivity, the reliability of functional connectivity during naturalistic viewing has not yet been fully established. The current study investigates the intra‐session reliability of functional connectivity during naturalistic viewing sessions to extend its understanding. Using fMRI data of 24 subjects measured at rest as well as during six naturalistic viewing conditions, we quantified the split‐half reliability of each condition, as well as cross‐condition reliabilities. We find that intra‐session reliability is relatively high for all conditions. While cross‐condition reliabilities are higher for pairings of two naturalistic viewing conditions, split‐half reliability is highest for the resting state. Potential sources of variability across the conditions, as well as the strengths and limitations of using intra‐session reliability as a measure in naturalistic viewing, are discussed. By enhancing the understanding of the reliability of naturalistic fMRI, our study supports future research that relates data measured during this increasingly popular experimental condition to behavioral or clinical characteristics. It demonstrates that the intra‐session reliability of functional connectivity is comparably high during six naturalistic viewing conditions and rest, includes a discussion of potential sources of variability, and a comparison across four anatomical atlases. [ABSTRACT FROM AUTHOR]

This article presents the application of a segmentation algorithm based on numerical solution of a partial differential equation of the level set type with incorporated a priori knowledge of the processed data. The semi-implicit complementary-volume numerical scheme is used to derive the algorithm. In particular, we focus on the segmentation of the left heart ventricle from the cardiac MRI data. Using a suitable modification of the level set equation together with an image thresholding, the objects in the image such as the left ventricle or the papillary muscles can be detected. The purpose of the article is to indicate how the algorithm parameters are set up and how the a priori knowledge helps to getting satisfactory segmentation results. [ABSTRACT FROM AUTHOR]

Purpose: To assess white matter changes after the first episode of schizophrenia by using fixel-based analysis (FBA). Methods: Diffusion weighted MR images were used to prospectively compare white matter microstructure between subjects after the first episode of schizophrenia (n = 16) and healthy controls (n = 22). The subjects were examined on a 3 Tesla MRI system equipped with a 64-channel head coil. FBA was performed using MRtrix software package (version 3.0.1). Results: A limited area of fibre density decrease was found in the anterior commissure. No fixels of fibre cross-section changes were found. For combined metric of fibre density and cross-section only one statistically significant fixel was found in the right frontal white matter. Conclusion: Using FBA, only a limited area of white matter microstructure corruption was found after the first episode of schizophrenia. Changes were located mainly in the anterior commissure. Compared to other published studies using FBA, the extent of changes is distinctly smaller which can be among other causes subjected to earlier stages of the illness of subjects included in this study. [ABSTRACT FROM AUTHOR]

We evaluated the clinical utility of cardiac magnetic resonance imaging (CMR) combined with a novel high-sensitivity troponin T assay (hs-cTnT) in the diagnosis of inflammatory cardiomyopathy. CMR, measurement of hs-cTnT, and endomyocardial biopsy were performed in 42 patients with dilated cardiomyopathy and a short-term history of heart failure (median 2 months, interquartile range 1 to 3.5). The patients were followed up for 25 ± 9 months for events. Endomyocardial biopsy revealed myocarditis in 15 subjects (36%). The sensitivity, specificity, and diagnostic accuracy of the individual CMR tissue parameters for myocardial inflammation was 40%, 96%, and 76% for early gadolinium enhancement, 87%, 44%, and 60% for late gadolinium enhancement, 47%, 89%, and 74% for pericardial effusion, and 67%, 85%, and 79% for any 2 of the criteria simultaneously, respectively. An assessment of myocardial edema on T2-weighted imaging and/or hs-cTnT assay were inadequate for the diagnosis. The extent of late gadolinium enhancement and increased hscTnT concentration were significant predictors of a composite end point of cardiac death, urgent heart transplantation, and hospitalization for worsening heart failure (hazard ratio 1.1, 95% confidence interval 1.0 to 1.2, per percentage of left ventricular mass; and hazard ratio 2.2, 95% confidence interval 1.4 to 3.5, per ln ng/L; p = 0.008 and p = 0.001, respectively). In conclusion, the results of the present study have demonstrated a modest performance for CMR and a limited use of the hs-cTnT assay in the diagnosis of inflammatory cardiomyopathy. Nonetheless, in these patients, CMR and/or hs-cTnT assessment seems to be useful for the prediction of the clinical outcome [ABSTRACT FROM AUTHOR]

Abstract: For the purpose of DT-MRI data visualization, an algorithm based on a numerical model of texture diffusion is proposed. As a prerequisite of entering clinical use, its parameters need to be adjusted properly so that the procedure gives satisfactory results with limited computational resources and time available. This contribution introduces the principles of the method and reports on the results of extensive computational studies aimed at finding optimal settings of the numerical scheme and model parameters with respect to visualization purposes. Total variation is used as a measure of visual quality of the produced images. Further, we provide evidence that using the algorithm is fully feasible on state of the art hardware. Finally, high resolution visualizations based on real data are demonstrated. [Copyright &y& Elsevier]

Abstract: FOXP2, the first gene known to be involved in the development of speech and language, can be considered to be, a priori, a candidate gene in schizophrenia, given the mounting evidence that the underlying core deficit in this disease could be a failure of structures relevant to normal language processing. To investigate the potential link between grey matter concentration (GMC) changes in patients with schizophrenia and the FOXP2 rs2396753 polymorphism previously reported to be associated with hallucinations in schizophrenia, we analysed high-resolution anatomical magnetic resonance images of 40 genotyped patients with schizophrenia and 36 healthy controls, using optimised voxel-based morphometry (VBM). Here we show that the common SNP rs2396753 (C>A) gene variant of the FOXP2 gene has significant effects on GMC in patients with schizophrenia, within regions of the brain known to be affected by this disease. Our data suggest that GMC reductions in schizophrenia may be driven by C allele carriers of the FOXP2 gene variant. [Copyright &y& Elsevier]

Abstract: Whole-brain voxel-based morphometry (VBM) studies provide support for orbitofrontal, medial frontal as well as for dorsal cortical volumetric alteration in obsessive-compulsive disorder (OCD). However, there is still a need to replicate a priori unpredicted findings and to elucidate white matter volumetric abnormalities and relationships between grey (GM) and white (WM) matter volume and clinical characteristics of OCD. We compared GM and WM volume in a group of 14 patients with OCD and 15 healthy controls using a 3T MRI scanner and an optimized VBM protocol. Regression analysis was used to examine relationships between GM and WM volume and clinical variables. In OCD we have found total WM volume reduction and marked mediofrontal, right temporo-parieto-occipital, right precentral, left middle temporal, left cerebellar and bilateral pons and mesencephalon GM volume reduction in the voxel-based analysis (p ≤0.05, FDR corrected, extent threshold 100 voxels). Regression analysis indicated a positive relationship between left orbitofrontal GM volume and severity of obsessive-compulsive symptoms and a negative relationship between symptom severity and GM volume in supramarginal gyri. Earlier age of OCD onset and longer illness duration were associated with smaller left occipital GM and right parietal WM and with greater left medial frontal GM and left frontal WM (p ≤0.001, uncorrected, extent threshold 50 voxels). Our results confirm volumetric abnormalities in the medial frontal and dorsal cortical areas in OCD. The relationships between OCD and clinical variables provide further evidence that frontal, parietal and occipital structures play a role in the disorder. [Copyright &y& Elsevier]

Functional connectivity analysis of resting‐state fMRI data has recently become one of the most common approaches to characterizing individual brain function. It has been widely suggested that the functional connectivity matrix is a useful approximate representation of the brain's connectivity, potentially providing behaviorally or clinically relevant markers. However, functional connectivity estimates are known to be detrimentally affected by various artifacts, including those due to in‐scanner head motion. Moreover, as individual functional connections generally covary only very weakly with head motion estimates, motion influence is difficult to quantify robustly, and prone to be neglected in practice. Although the use of individual estimates of head motion, or group‐level correlation of motion and functional connectivity has been suggested, a sufficiently sensitive measure of individual functional connectivity quality has not yet been established. We propose a new intuitive summary index, Typicality of Functional Connectivity, to capture deviations from standard brain functional connectivity patterns. In a resting‐state fMRI dataset of 245 healthy subjects, this measure was significantly correlated with individual head motion metrics. The results were further robustly reproduced across atlas granularity, preprocessing options, and other datasets, including 1,081 subjects from the Human Connectome Project. In principle, Typicality of Functional Connectivity should be sensitive also to other types of artifacts, processing errors, and possibly also brain pathology, allowing extensive use in data quality screening and quantification in functional connectivity studies as well as methodological investigations. [ABSTRACT FROM AUTHOR]

Purpose: To asses cerebral cortical thickness and area changes in the earliest stage of schizophrenia. Methods: Magnetic resonance was used to prospectively compare cerebral cortex thickness and surface area between subjects after the first episode of schizophrenia (n = 15) and healthy controls (n = 19). The subjects were examined on a 3 Tesla MRI system equipped with a 64-channel head coil. Surface-based morphometry was performed on 3D T1- and T2-weighted data by using Freesurfer software package (ver. 7.1.0). Results: No statistically significantly different clusters of cerebral cortical surface / thickness were found between both groups of subjects. Conclusion: Contrary to the observations published by other authors including large multicentric studies, no statistically significant differences in cerebral cortical thickness or area were found in the earliest stage of schizophrenia. [ABSTRACT FROM AUTHOR]

Aim: The aim of this project is to assess the feasibility Gd-DOTA- (Dotarem) for imaging of hyalinne cartilage using delayed gadoliniumenhanced magnetic resonance imaging of cartilage (dGEMRIC) to replace Gd-DTPA2- (Magnevist). Methods: The project was a part of a study of postoperative cartilage changes. MR examination was performed on a Philips Ingenia 3T using a 8-channels dS knee coil, dGEMRIC 3D IR-GRE sequence with five different inversion times (100, 200, 400, 800 and 1600 ms), voxel: 0.5 × 0.5 × 3 mm3, FOV 160 mm, 40 slices, TR 1800 ms, TE 2 ms, 8 ° flip angle, SENSE factor 2. The baseline examination was performed before surgery (M0), 6 months (M6), 12 (M12) and 18 (M18) months after surgery. Comparisons were made in these groups of patients: 11 patients with Magnevist at initial examination M0 and M6, 8 patients with Magnevist at M0 and Dotarem in M6, and finally 6 patients with Dotarem at M0 and also M6 examination. Results: The median values of the index change were similar in the Magnevist-Magnevist and Dotarem-Dotarem groups (2.7 and 2.4, respectively, p = 0.961 before correction and 1.000 after correction for multiple comparisons). The median index change in the Magnevist-Dotarem group was higher (4.8) compared to the two other groups, but the difference was not statistically significant (p = 0.351 and p = 0.662 before correction; 1.000 in both cases after correction). Conclusion: dGEMRIC is feasible using Gd- DOTA- (Dotarem), there was no statistically significant difference (p = 0. 637) between the two types of contrast media. [ABSTRACT FROM AUTHOR]

In the last years, there has been a considerable increase of research into the neuroimaging correlates of inter-individual temperament and character variability—an endeavour for which the term 'personality neuroscience' was coined. Among other neuroimaging modalities and approaches, substantial work focuses on functional connectivity in resting state (rs-FC) functional magnetic resonance imaging data. In the current paper, we set out to independently query the questions asked in a highly cited study that reported a range of functional connectivity correlates of personality dimensions assessed by the widely used 'Big Five' Personality Inventory. Using a larger sample (84 subjects) and an equivalent data analysis pipeline, we obtained widely disagreeing results compared to the original study. Overall, the results were in line with the hypotheses of no relation between functional connectivity and personality, when more precise permutation-based multiple testing procedures were applied. The results demonstrate that as with other neuroimaging studies, great caution should be applied when interpreting the findings, among other reasons due to multiple testing problem involved at several levels in many neuroimaging studies. Of course, the current study results can not ultimately disprove the existence of some link between personality and brain's intrinsic functional architecture, but clearly shows that its form is very likely different and much more subtle and elusive than was previously reported. [ABSTRACT FROM AUTHOR]

Background: Cannabis, and specifically one of its active compounds delta-9-tetrahydrocannabinol in recreational doses, has a variety of effects on cognitive processes. Most studies employ resting state functional magnetic resonance imaging techniques to assess the stationary effects of cannabis and to-date one report addressed the impact of delta-9-tetrahydrocannabinol on the dynamics of whole-brain functional connectivity.Methods: Using a repeated-measures, within-subjects design, 19 healthy occasional cannabis users (smoking cannabis ⩽2 per week) underwent resting state functional magnetic resonance imaging scans. Each subject underwent two scans: in the intoxicated condition, shortly after smoking a cannabis cigarette, and in the non-intoxicated condition, with the subject being free from cannabinoids for at least one week before. All sessions were randomized and performed in a four-week interval. Data were analysed employing a standard independent component analysis approach with subsequent tracking of the functional connectivity dynamics, which allowed six connectivity clusters (states) to be individuated.Results: Using standard independent component analysis in resting state functional connectivity, a group effect was found in the precuneus connectivity. With a dynamic independent component analysis approach, we identified one transient connectivity state, characterized by high connectivity within and between auditory and somato-motor cortices and anti-correlation with subcortical structures and the cerebellum that was only found during the intoxicated condition. Behavioural measures of the subjective experiences of changed perceptions and tetrahydrocannabinol plasma levels during intoxication were associated with this state.Conclusions: With the help of the dynamic connectivity approach we could elucidate neural correlates of the transitory perceptual changes induced by delta-9-tetrahydrocannabinol in cannabis users, and possibly identify a biomarker of cannabis intoxication. [ABSTRACT FROM AUTHOR]

Highlights • Study shows 44 brain regions volume changes with Alzheimer's disease. • Volumes were calculated both in absolute values and ratios to the whole brain volume. • The hippocampo-horn proportion is effective for hippocampal atrophy evaluation. • This method can be simplified for visual assessment. Abstract Ratios between opposing volumes from brain magnetic resonance imaging (MRI) can provide additional information to volumes in Alzheimer's disease (AD). Brain three-dimensional MPRAGE MRI at 3T were segmented into 44 regions using FreeSurfer v6 in 75 participants. The region's size in absolute volumes and relative proportions to the whole brain volume were compared between 39 AD patients and 36 age-, education- and sex-matched normal controls (NC). Volumes of the most atrophied parts were related to the opposing volumes of the most enlarged parts as ratios. The most atrophic structures in AD were both hippocampi. By contrast, the greatest enlargements in AD were inferior parts of both lateral ventricles. The best ratio for each side was the hippocampo-horn proportion calculated as ratio: the hippocampus / (the hippocampus + inferior lateral ventricle). Its optimal cut-off of 74% yielded sensitivity of 74% and specificity of 78% on the left and sensitivity of 74% and specificity of 78% on the right. The hippocampo-horn proportion is another measure to evaluate the degree of hippocampal atrophy on brain MRI in percentages. It has a potential to be simplified into a comparison of two-dimensional corresponding areas or a visual assessment. [ABSTRACT FROM AUTHOR]

Purpose: To assess microstructural changes of the cerebral white matter in the earliest stage of schizophrenia. Methods: Magnetic resonance was used to prospectively compare fractional anisotropy of the white matter between subjects after the first episode of schizophrenia (n = 23) and healthy controls (n = 23). Diffusion tensor data obtained from multidirectional diffusion weighted sequence were analysed by using Tract-Based Spatial Statistics (TBSS). Results: Extensive areas of decreased fractional anisotropy (FA) were found in the white matter after the first episode of schizophrenia, affecting most of the white matter tracts. No areas of significantly increased FA were found when compared to the healthy control group. Conclusion: Extensive areas of microstructural alteration of the white matter are already present during the first episode of schizophrenia. [ABSTRACT FROM AUTHOR]

Abstract Background Cardiac resynchronization therapy (CRT) improves symptoms of heart failure (HF), morbidity and mortality in selected population. The aim of the study was to investigate the impact of cardiac magnetic resonance (CMR)-guided left ventricular (LV) lead placement on clinical outcomes and LV reverse remodelling in CRT recipients. Methods Patients with CRT indication were randomized for CMR-guided (CMR group) or electrophysiologically guided (EP group) LV lead placement between 2011 and 2014. The target site in the CMR group was defined as the most delayed, scar-free, in the EP group as the site with the longest interval between the QRS onset and local electrogram. The primary endpoint was a combination of cardiovascular death or HF hospitalization. Secondary endpoints were New York Heart Association (NYHA) Class improvement ≥1, LV endsystolic diameter reduction >10%, B-type natriuretic peptide reduction by ≥30%. Results A total of 99 patients (47 in the CMR and 52 in the EP group) were enrolled. During a median follow-up of 47 months, primary composite endpoint occurred in 5 patients in the CMR group and 14 patients in the EP group (HR = 0.46; 95% CI: 0.16–1.32). Patients with left bundle branch block and NYHA Class >2 had better clinical outcome in the CMR group (HR = 0.09; 95% CI: 0.01–0.75). Conclusions The use of CMR did not result in significant reduction of combined endpoint of cardiovascular death or HF hospitalization in the total study population. Significant clinical benefit from CMR-guided procedure was observed in a subgroup of optimum CRT candidates with advanced HF. Highlights • The first randomized study investigating the role of CMR in CRT • The study failed to show the impact of CMR on event-free survival in total cohort. • A subgroup of patients with LBBB and NYHA >2 derived a clear benefit from the CMR. [ABSTRACT FROM AUTHOR]

In this study, we use separate eye-tracking measurements and functional magnetic resonance imaging to investigate the neuronal and behavioral response to painted portraits with direct versus averted gaze. We further explored modulatory effects of several painting characteristics (premodern vs modern period, influence of style and pictorial context). In the fMRI experiment, we show that the direct versus averted gaze elicited increased activation in lingual and inferior occipital and the fusiform face area, as well as in several areas involved in attentional and social cognitive processes, especially the theory of mind: angular gyrus/temporo-parietal junction, inferior frontal gyrus and dorsolateral prefrontal cortex. The additional eye-tracking experiment showed that participants spent more time viewing the portrait's eyes and mouth when the portrait's gaze was directed towards the observer. These results suggest that static and, in some cases, highly stylized depictions of human beings in artistic portraits elicit brain activation commensurate with the experience of being observed by a watchful intelligent being. They thus involve observers in implicit inferences of the painted subject's mental states and emotions. We further confirm the substantial influence of representational medium on brain activity. [ABSTRACT FROM AUTHOR]

Early cardiac magnetic resonance imaging (CMR) scans were of inferior quality. A significant improvement in image quality was achieved after introducing the segmented acquisition of the k-space synchronized with patient's ECG, performed either in breath hold or free breathing. CMR is now used widely in the clinical setting for assessment of cardiac chamber volumes, global and regional cardiac contraction, morphology and tissue characterization. Inflammatory or post-myocardial infarction changes involve sequences which can appreciate myocardial edema or the use of late post-gadolinium contrast enhancement (LGE) to visualise diffuse or focal scar. Other applications include the assessment of valvular stenosis or regurgitation by means of flow measurement through a defined orifice and first pass myocardial perfusion to assess ischemia. Last but not least, CMR is increasingly used for the assessment of congenital heart diseases, in which CMR offers objective and directly comparable measures during serial examinations, without any radiation exposure. [ABSTRACT FROM AUTHOR]

Complex systems are commonly characterized by the properties of their graph representation. Dynamical complex systems are then typically represented by a graph of temporal dependencies between time series of state variables of their subunits. It has been shown recently that graphs constructed in this way tend to have relatively clustered structure, potentially leading to spurious detection of small-world properties even in the case of systems with no or randomly distributed true interactions. However, the strength of this bias depends heavily on a range of parameters and its relevance for real-world data has not yet been established. In this work, we assess the relevance of the bias using two examples of multivariate time series recorded in natural complex systems. The first is the time series of local brain activity as measured by functional magnetic resonance imaging in resting healthy human subjects, and the second is the time series of average monthly surface air temperature coming from a large reanalysis of climatological data over the period 1948-2012. In both cases, the clustering in the thresholded correlation graph is substantially higher compared with a realization of a density-matched random graph, while the shortest paths are relatively short, showing thus distinguishing features of small-world structure. However, comparable or even stronger small-world properties were reproduced in correlation graphs of model processes with randomly scrambled interconnections. This suggests that the small-world properties of the correlation matrices of these real-world systems indeed do not reflect genuinely the properties of the underlying interaction structure, but rather result from the inherent properties of correlation matrix. [ABSTRACT FROM AUTHOR]

The present report presents a rare case in which a patient with pituitary apoplexy (PA) without compression of the optic chiasm experienced diagnosable visual impairment in the ensuing months. Endocrinologically, the condition was a prolactinoma followed by bleeding into the pituitary gland. Due to the unexplained functional changes in the patient, an electrophysiological examination (pattern electroretinogram and pattern visual evoked potentials) was performed, which verified a bilateral non-inflammatory neurogenic lesion. This finding was confirmed by functional magnetic resonance imaging (fMRI) examination. Structural MRI did not reveal chiasm compression in the time sequence or alteration of the optic nerves (the diameter of the optic nerve at different distances from the eye and the diameter of the optic nerve sheath at different distances from the eye). Similarly, neither the retinal nerve fiber layer (RNFL) nor the vessel density was altered. The present report suggests that changes in visual fields may be due to ischemia in the area of the chiasm and optic nerves, similar to PA. [ABSTRACT FROM AUTHOR]

Purpose: To assess the entire geometric and dosimetric (relative) uncertainties of the radiosurgery procedure with the Leksell gamma knife.Materials and methods: The entire Leksell gamma knife stereotactic radiosurgery treatment procedure was simulated with the use of a special water filled head phantom and polymer-gel dosimeter evaluated by nuclear magnetic resonance (NMR). A test vessel filled with the polymer-gel dosimeter was fixed in the head phantom. The phantom underwent stereotactic NMR imaging, treatment planning and then irradiation according to the treatment plan prepared exactly the same way as in the ordinary treatment procedure for a patient. The treatment plan was represented by one isocenter positioned approximately centrally in the head phantom. This procedure was subsequently repeated for all four collimators (4, 8, 14, 18 mm) used on the Leksell gamma knife. Evaluation of dosimeters was performed on a Siemens EXPERT 1 T NMR scanner. Dose profiles in X, Y and Z axes through the ellipsoidal shaped dose distribution were obtained to compare experimental results from the irradiated phantom with the treatment planning system calculations.Results: Reasonable agreement was observed between the treatment planning system calculations of relative dose distribution and the measured data. The maximum observed deviation in the spatial position between the center of the measured and calculated dose profiles was 0.6 mm. The maximum observed difference in full width of half maximum between calculated and measured profiles was 1.2 mm.Conclusions: The use of polymer-gel dosimetry for a verification of stereotactic procedures has some unique advantages that can be summarized as follows: the dosimeter itself is tissue equivalent, three-dimensional dose distributions can be measured and the dosimeter allows simulation of the patient''s procedures without any limitations. [Copyright &y& Elsevier]