Introduction Hemodynamics is thought to play a very important role in the initiation, growth, and rupture of intracranial aneurysms. The purpose of our study was to compare hemodynamics of intracranial aneurysms of MR fluid dynamics (MRFD) using 3D cine PC MR imaging (4D-Flow) at 1.5 T and MR-based computational fluid dynamics (CFD). Methods 4D-Flow was performed for five intracranial aneurysms by a 1.5 T MR scanner. 3D TOF MR angiography was performed for geometric information. The blood flow in the aneurysms was modeled using CFD simulation based on the finite element method. We used MR angiographic data as the vascular models and MR flow information as boundary conditions in CFD. 3D velocity vector fields, 3D streamlines, shearing velocity maps, wall shear stress (WSS) distribution maps and oscillatory shear index (OSI) distribution maps were obtained by MRFD and CFD and were compared. Results There was a moderate to high degree of correlation in 3D velocity vector fields and a low to moderate degree of correlation in WSS of aneurysms between MRFD and CFD using regression analysis. The patterns of 3D streamlines were similar between MRFD and CFD. The small and rotating shearing velocities and higher OSI were observed at the top of the spiral flow in the aneurysms. The pattern and location of shearing velocity in MRFD and CFD were similar. The location of high oscillatory shear index obtained by MRFD was near to that obtained by CFD. Conclusion MRFD and CFD of intracranial aneurysms correlated fairly well.

Healthy aging is associated with structural and functional changes in the brain even in individuals who are free of neurodegenerative diseases. Using resting state functional magnetic resonance imaging data from a carefully selected cohort of participants, we examined cross sectional changes in the functional organization of several large-scale brain networks over the adult lifespan and its potential association with general cognitive performance. Converging results from multiple analyses at the voxel, node, and network levels showed widespread reorganization of functional brain networks with increasing age. Specifically, the primary processing (visual and sensorimotor) and visuospatial (dorsal attention) networks showed diminished network integrity, while the so-called core neurocognitive (executive control, salience, and default mode) and basal ganglia networks exhibited relatively preserved between-network connections. The visuospatial and precuneus networks also showed significantly more widespread increased connectivity with other networks. Graph analysis suggested that this reorganization progressed towards a more integrated network topology. General cognitive performance, assessed by Addenbrooke’s Cognitive Examination-Revised total score, was positively correlated with between-network connectivity among the core neurocognitive and basal ganglia networks and the integrity of the primary processing and visuospatial networks. Mediation analyses further indicated that the observed association between aging and relative decline in cognitive performance could be mediated by changes in relevant functional connectivity measures. Overall, these findings provided further evidence supporting widespread age-related brain network reorganization and its potential association with general cognitive performance during healthy aging.

Autistic disorder is associated with deficits in social function. The disorder may be related to dysfunction in the brain regions that are involved in the process of recognising facial expressions of other persons. Using fMRI, we investigated whether autistic patients with relatively high IQ would have different brain activation on the tasks of recognition of facial expressions (i.e. faces expressing disgust, fear, and happiness) compared with normal control subjects. In disgust and fear recognition tasks, there were different patterns of brain activation in the cortico-limbic neural circuits qbetween autistic and normal groups. Patients with autistic disorder may have difficulty in grasping facially expressed qemotions in others, and thereby cannot manipulate the interpersonally derived information.

Each intracranial aneurysm in this study had at least one spiral flow. The WSS was lower and OSI was higher at the apex of the spiral flow than the whole aneurysmal wall.

Following the chronic use of methamphetamine, some individuals experience psychosis and anxiety. One reason may be the persistence of metabolite abnormalities in the brain of currently abstinent former methamphetamine users.In this study, N-acetylaspartate (NAA), creatine plus phosphocreatine (Cr ϩ PCr), and choline-containing compound (Cho) levels were measured in the left and right basal ganglia using proton magnetic resonance spectroscopy (MRS) The number of abusers of the highly addictive drug methamphetamine has risen substantially worldwide and this has raised important concerns (Woolverton et al. 1984;Baberg et al. 1996;Shaw 1999). For example, chronic methamphetamine users show psychosis and anxiety following intoxication and withdrawal (Seivewright 2000). In addition, in some individuals, these psychiatric states may be present for months or even years after cessation of methamphetamine use (Sato et al. 1992;Iwanami et al. 1994;Buffenstein et al. 1999;Iyo et al. 1999). Although there are growing clinical observations on the neurotoxicology of chronic methamphetamine use, the mechanism by which the residual psychiatric problems arise from chronic methamphetamine NO . 3 use remains unknown. In rodents and baboons, methamphetamine has been shown to be toxic to dopaminergic and serotonergic neurons (Nakayama et al. 1993;Villemagne et al. 1998;Kokoshka et al. 1998). These neurotoxic effects include decreased concentrations of dopamine and serotonin in the brain and a reduction of dopamine and serotonin transporters, as well as loss of ATP and mitochondrial dysfunction in dopaminergic neurons (Chan et al. 1994;Burrows et al. 2000;Lotharius and O'Malley 2001). Human positron emission tomography (PET) studies have reported a significant reduction of dopamine transporter density in methamphetamine users Volkow et al. 2001), and that the reduction observed in methamphetamine users is associated with psychomotor impairment (Volkow et al. 2001). Recently, we have also found that the dopamine transporter density in methamphetamine users is inversely related to the length of methamphetamine use and the magnitude of psychiatric symptoms, including psychotic symptoms (Sekine et al. 2001).In vivo proton magnetic resonance spectroscopy ( 1 H MRS) and its variant 1 H MRS techniques provide insight into the metabolism of several endogenous brain chemicals (Miller 1991;Jackson 1992). A recent 1 H MRS study showed evidence for long-term metabolite alterations in currently abstinent former methamphetamine users, that is, reduced concentration of both N-acetylaspartate (NAA) and creatine plus phosphocreatine (Cr ϩ PCr) in the right basal ganglia (Ernst et al. 2000). However, it is unclear whether these abnormalities detected by 1 H MRS are related to psychiatric symptoms that are frequently observed in abstinent methamphetamine users.In this study, we investigated changes of the chemistry in the basal ganglia of abstinent methamphetamine users by 1 H MRS, and examined any relationship between the changes and clinical cha...

Purpose:To visualize the hemodynamics of the intracranial arteries using time-resolved three-dimensional phasecontrast (PC)-MRI (4D-Flow). Materials and Methods:MR examinations were performed with a 1.5T MR unit on six healthy volunteers (22-50 years old, average ϭ 30 years). 4D-Flow was based on a radiofrequency (RF)-spoiled gradient-echo sequence, and velocity encoding (VENC) was performed along all three spatial directions. Measurements were retrospectively gated to the electrocardiogram (ECG), and cine series of three-dimensional (3D) data sets were generated. The voxel size was 1 ϫ 1 ϫ 1 mm, and acquisition time was 30 -40 minutes. 4D data sets were calculated into time-resolved images of 3D streamlines, 3D particle traces, and 2D velocity vector fields by means of flow visualization software. Results:We were able to see the 3D streamlines from the circle of Willis to the bilateral M2 segment of the middle cerebral arteries (MCAs). Time-resolved images of 3D particle traces also clearly demonstrated intracranial arterial flow dynamics. 2D velocity vector fields on the planes traversing the carotid siphon or the basilar tip were clearly visualized. These results were obtained in all six volunteers. Conclusion:4D-Flow helped to elucidate the in vivo 3D hemodynamics of human intracranial arteries. This method may be a useful noninvasive means of analyzing the hemodynamics of intracranial arteries in vivo.

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4D-Flow identified hemodynamic changes in celiaco-mesenteric arteries in patients with PDA aneurysms with concomitant CA occlusion. These hemodynamic changes may be associated with PDA aneurysm formation.