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1.
Magn Reson Med ; 65(4): 1043-52, 2011 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-21413068

RESUMO

A new method to investigate anomalous diffusion in human brain, inspired by the stretched-exponential model proposed by Hall and Barrick, is proposed here, together with a discussion about its potential application to cerebral white matter characterization. Aim of the work was to show the ability of anomalous diffusion indices to characterize white matter structures, whose complexity is only partially accounted by diffusion tensor imaging indices. MR signal was expressed as a stretched-exponential only along the principal axes of diffusion; whereas, in a generic direction, it was modeled as a combination of three stretched-exponentials. Indices to quantify the tissue anomalous diffusion and its anisotropy, independently of the experiment reference frame, were derived. Experimental results, obtained on 10 healthy subjects at 3T, show that the new parameters are highly correlated to intrinsic local geometry when compared with Hall and Barrick indices. Moreover, they offer a different contrast in white matter regions when compared with diffusion tensor imaging. Specifically, the new indices show a higher capability to discriminate among areas of the corpus callosum associated to different distribution in axonal densities, thus offering a new potential tool to detect more specific patterns of brain abnormalities than diffusion tensor imaging in the presence of neurological and psychiatric disorders.


Assuntos
Algoritmos , Artefatos , Encéfalo/anatomia & histologia , Imagem de Difusão por Ressonância Magnética/métodos , Aumento da Imagem/métodos , Interpretação de Imagem Assistida por Computador/métodos , Anisotropia , Feminino , Humanos , Masculino , Reprodutibilidade dos Testes , Sensibilidade e Especificidade , Adulto Jovem
2.
J Neurol Neurosurg Psychiatry ; 82(1): 58-66, 2011 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-20639384

RESUMO

OBJECTIVE: To assess the contribution of regional grey matter (GM) atrophy and functional disconnection in determining the level of cognitive decline in patients with Alzheimer's disease (AD) at different clinical stages. METHODS: Ten patients with amnesic mild cognitive impairment (a-MCI), 11 patients with probable AD and 10 healthy controls were recruited. T1 volumes were obtained from each subject and postprocessed according to an optimised voxel based morphometry protocol. Resting state functional MRI data were also collected from the same individuals and analysed to produce connectivity maps after identification of the default mode network (DMN) by independent component analysis. RESULTS: Compared with healthy controls, both AD and a-MCI patients showed a similar regional pattern of brain disconnection between the posterior cingulate cortex (PCC) and the medial prefrontal cortex and the rest of the brain. Conversely, the distribution of GM atrophy was significantly more restricted in a-MCI than in AD patients. Interestingly, the PCC showed reduced connectivity in a-MCI patients in the absence of GM atrophy, which was, in contrast, detectable at the stage of fully developed AD. CONCLUSIONS: This study indicates that disconnection precedes GM atrophy in the PCC, which is a critical area of the DMN, and supports the hypothesis that GM atrophy in specific regions of AD brains likely reflects a long term effect of brain disconnection. In this context, our study indicates that GM atrophy in PCC accompanies the conversion from MCI to AD.


Assuntos
Doença de Alzheimer/patologia , Encéfalo/patologia , Vias Neurais/patologia , Idoso , Doença de Alzheimer/psicologia , Amnésia/patologia , Amnésia/psicologia , Atrofia , Transtornos Cognitivos/patologia , Transtornos Cognitivos/psicologia , Progressão da Doença , Feminino , Humanos , Processamento de Imagem Assistida por Computador , Imageamento por Ressonância Magnética , Masculino , Pessoa de Meia-Idade , Rede Nervosa/patologia , Testes Neuropsicológicos
3.
Phys Med Biol ; 55(19): 5767-85, 2010 Oct 07.
Artigo em Inglês | MEDLINE | ID: mdl-20844335

RESUMO

Here we propose a new magnetic resonance (MR) strategy based on the evaluation of internal gradient (G(i)) to assess the trabecular bone (TB) density in spongy bone. Spongy bone is a porous system characterized by a solid trabecular network immersed in bone marrow and characterized by a different relative percentage of water and fats. Using a 9.4 T MR micro-imaging system, we first evaluated the relative water and fat G(i) as extracted from the Spin-Echo decay function in vitro of femoral head samples from calves. Indeed, the differential effects of fat and water diffusion result in different types of G(i) behavior. Using a clinical MR 3T scanner, we then investigated in vivo the calcanei of individuals characterized by different known TB densities. We demonstrate, on these samples, that water is more prevalent in the boundary zone, while fats are rearranged primarily in the central zone of each pore. In vitro experiments showed that water G(i) magnitude from the samples was directly proportional to their TB density. Similar behavior was also observed in the clinical measures. Conversely, fat G(i) did not provide any information on spongy-bone density. Our results suggest that water G(i) may be a reliable marker to assess the status of spongy bone.


Assuntos
Densidade Óssea , Cabeça do Fêmur/fisiologia , Imageamento por Ressonância Magnética/métodos , Adulto , Idoso , Animais , Difusão , Humanos , Masculino , Pessoa de Meia-Idade , Osteoporose/diagnóstico , Osteoporose/fisiopatologia , Reprodutibilidade dos Testes , Adulto Jovem
4.
Appl Radiat Isot ; 67(7-8 Suppl): S34-6, 2009 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-19375337

RESUMO

One of the main limitations for BNCT effectiveness is the insufficient intake of (10)B nuclei within tumour cells. This work was aimed at investigating the use of L-DOPA as enhancer for boronophenylalanine (BPA) uptake in the C6 glioma model. The investigation was first performed in vitro, and then extended in vivo to the animal model. BPA accumulation in C6 glioma cells was assessed, using radiowave dielectric spectroscopy (RDS), with and without L-DOPA preloading. C6 glioma cells were also implanted in the brain of 25 rats, randomly assigned to two experimental branches: (1) intra-carotid BPA infusion; (2) intra-carotid BPA infusion after pre-treatment with L-DOPA, administrated 24 h before BPA infusion. All animals were sacrificed, and assessment of BPA concentrations in tumour tissue, normal brain, and blood samples was performed using high performance liquid chromatography (HPLC). L-DOPA preloading induced a massive increase of BPA concentration either in vitro on C6 glioma cells or in vivo in the animal model tumour. Moreover, no significant difference was found in the normal brain and blood samples between the two animal groups. This study suggests the potential use of L-DOPA as enhancer for BPA accumulation in malignant gliomas eligible for BNCT.


Assuntos
Compostos de Boro/administração & dosagem , Compostos de Boro/farmacocinética , Neoplasias Encefálicas/metabolismo , Glioma/metabolismo , Levodopa/administração & dosagem , Fenilalanina/análogos & derivados , Radiossensibilizantes/administração & dosagem , Radiossensibilizantes/farmacocinética , Animais , Compostos de Boro/uso terapêutico , Terapia por Captura de Nêutron de Boro , Neoplasias Encefálicas/patologia , Neoplasias Encefálicas/radioterapia , Linhagem Celular Tumoral , Glioma/patologia , Glioma/radioterapia , Técnicas In Vitro , Imageamento por Ressonância Magnética , Masculino , Fenilalanina/administração & dosagem , Fenilalanina/farmacocinética , Fenilalanina/uso terapêutico , Radiossensibilizantes/uso terapêutico , Ratos , Ratos Wistar
5.
Appl Radiat Isot ; 67(7-8 Suppl): S365-8, 2009 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-19375924

RESUMO

The aim of this study was to evaluate in vivo the boron biodistribution and pharmacokinetics of 4-borono-2-fluorophenylalanine ((19)F-BPA) using (19)F MR Imaging ((19)F MRI) and Spectroscopy ((19)F MRS). The correlation between the results obtained by both techniques, (19)F MRI on rat brain and (19)F MRS on blood samples, showed the maximum (19)F-BPA uptake in C6 glioma model at 2.5h after infusion determining the optimal irradiation time. Moreover, the effect of L-DOPA as potential enhancer of (19)F-BPA tumour intake was assessed using (19)F MRI.


Assuntos
Compostos de Boro/farmacocinética , Terapia por Captura de Nêutron de Boro/métodos , Flúor/análise , Flúor/farmacocinética , Imageamento por Ressonância Magnética/métodos , Espectroscopia de Ressonância Magnética/métodos , Fenilalanina/análogos & derivados , Animais , Compostos de Boro/uso terapêutico , Neoplasias Encefálicas/metabolismo , Neoplasias Encefálicas/radioterapia , Linhagem Celular Tumoral , Glioma/metabolismo , Glioma/radioterapia , Técnicas In Vitro , Masculino , Fenilalanina/farmacocinética , Fenilalanina/uso terapêutico , Radiossensibilizantes/farmacocinética , Radiossensibilizantes/uso terapêutico , Ratos , Ratos Wistar , Distribuição Tecidual
6.
Neuroimage ; 41(4): 1228-41, 2008 Jul 15.
Artigo em Inglês | MEDLINE | ID: mdl-18474435

RESUMO

In this paper the possible use of the resonant mechanism between some spectral components of the neuronal activity and the spin dynamics in ultra-low field MRI experiments--for the implementation of the nc-MRI techniques and proposed by Kraus et al., 2008--is investigated by means of "realistic" simulations of the neuronal activity of a modelled neuronal network. Previously characterized digital neurons are used to reproduce neuronal currents based on biophysical details and the distribution of the local magnetic field inside a MRI cubic voxel (having a dimension of 1.2 mm) is evaluated. The properties of the water proton spin dynamics as a consequence of the neuronal field and of external applied fields are extrapolated integrating the Bloch equations. The characteristics of the expected MR signals are discussed in relation to the specifics of the NMR sequence used and to the properties of the neuronal activity. The great potentialities of the technique are provided by: a) the possible easy implementation of the technique, b) the possible cheap instrumentation required; c) the flexibility of the ultra-low field systems.


Assuntos
Imageamento por Ressonância Magnética/métodos , Algoritmos , Simulação por Computador , Campos Eletromagnéticos , Eletrofisiologia , Processamento de Imagem Assistida por Computador/estatística & dados numéricos , Magnetoencefalografia , Redes Neurais de Computação , Neurônios/fisiologia , Processamento de Sinais Assistido por Computador
7.
Neuroimage ; 39(1): 87-106, 2008 Jan 01.
Artigo em Inglês | MEDLINE | ID: mdl-17936018

RESUMO

Many efforts have been done in order to preview the properties of the magnetic resonance (MR) signals produced by the neuronal currents using simulations. In this paper, starting with a detailed calculation of the magnetic field produced by the neuronal currents propagating over single hippocampal CA1 pyramidal neurons placed inside a cubic MR voxel of length 1.2 mm, we proceeded on the estimation of the phase and magnitude MR signals. We then extended the results to layers of parallel and synchronous similar neurons and to ensembles of layers, considering different echo times, voxel volumes and neuronal densities. The descriptions of the neurons and of their electrical activity took into account the real neuronal morphologies and the physiology of the neuronal events. Our results concern: (a) the expected time course of the MR signals produced by the neuronal currents in the brain, based on physiological and anatomical properties; (b) the different contributions of post-synaptic potentials and of action potentials to the MR signals; (c) the estimation of the equivalent current dipole and the influence of its orientation with respect to the external magnetic field on the observable MR signal variations; (d) the size of the estimated neuronal current induced phase and magnitude MR signal changes with respect to the echo time, voxel-size and neuronal density. The inclusion of realistic neuronal properties into the simulation introduces new information that can be helpful for the design of MR sequences for the direct detection of neuronal current effects and the testing of bio-electromagnetic models.


Assuntos
Potenciais de Ação/fisiologia , Mapeamento Encefálico/métodos , Interpretação de Imagem Assistida por Computador/métodos , Imageamento por Ressonância Magnética/métodos , Potenciais da Membrana/fisiologia , Modelos Neurológicos , Neurônios/fisiologia , Simulação por Computador , Humanos , Rede Nervosa/fisiologia
8.
J Phys Chem B ; 111(25): 7092-7, 2007 Jun 28.
Artigo em Inglês | MEDLINE | ID: mdl-17536852

RESUMO

The aging of water suspension of the synthetic clay Laponite has been studied by liquid-state triple-quantum filter nuclear magnetic resonance techniques, in a range of clay weight concentration (Cw = 0.012-0.028) known as the isotropic phase. Counterions dynamic parameters (rotational correlation time tauc and quadrupolar coupling constant e2qQ/h) have been extracted from sodium triple-quantum filtered experimental data within the multi-exponential quadrupolar relaxation theory in the fast exchange approximation. By monitoring quadrupolar sodium ions dynamical (tauc and e2qQ/h) and static (counterion concentration pb) properties during the aging, we find two different mechanisms of transition toward an arrested state. Our experimental findings match with the description which states, at low concentration, the formation of clusters of Laponite disks trigger the reaching of the arrested state, while at high concentration, single disks are the basic units of the arrested phase. The procedure proposed in this paper, based on multiple quantum filtered NMR data analysis, results to be a useful means to study the routes to arrested states in aqueous colloidal dispersions.

9.
Solid State Nucl Magn Reson ; 28(2-4): 266-72, 2005 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-16360582

RESUMO

During the last decade, considerable effort has been invested into the development of diffusion tensor imaging (DTI) mainly used to investigate cerebral morphology. The aim of this paper is to review and to discuss our recent results about high magnetic field DTI application to study spongy bone tissue. Due to its peculiar properties, spongy bone represents a particular porous system sample. Strategies to perform DTI on porous systems and issues linked to DTI outcome interpretation are presented on the basis of our results concerning trabecular bone network characterization.


Assuntos
Imagem de Difusão por Ressonância Magnética , Fêmur/anatomia & histologia , Animais , Anisotropia , Bovinos , Porosidade
10.
Brain Res Bull ; 63(1): 1-5, 2004 Mar 01.
Artigo em Inglês | MEDLINE | ID: mdl-15121233

RESUMO

In the present work, an arteriovenous malformation was taken as a pathological model for studying task-related flow decreases during a motor task. Combined Blood Oxygen Level Dependent (BOLD)-perfusion experiments were applied in order to evaluate the relative sensitivity of these techniques to task-related reductions in cerebral blood flow (CBF). Results shows that, by matching the sensitivity of the methods (which exhibit a different contrast-to-noise ratio) in the primary motor cortex, the spatial extent of the regions of decreased perfusion signal is larger than those of the BOLD signal reduction. The above finding suggests that perfusion imaging, that already represents a gold standard method in the detection of vascular phenomena, may estimate task-related flow decreases in a functional time-series better than BOLD.


Assuntos
Circulação Cerebrovascular/fisiologia , Transtornos Cerebrovasculares/fisiopatologia , Malformações Arteriovenosas Intracranianas/fisiopatologia , Imageamento por Ressonância Magnética/métodos , Córtex Motor/fisiopatologia , Adulto , Artefatos , Mapeamento Encefálico , Transtornos Cerebrovasculares/etiologia , Humanos , Angiografia por Ressonância Magnética , Imageamento por Ressonância Magnética/normas , Masculino , Modelos Neurológicos , Córtex Motor/irrigação sanguínea , Consumo de Oxigênio/fisiologia , Valor Preditivo dos Testes , Reprodutibilidade dos Testes , Processamento de Sinais Assistido por Computador
11.
Solid State Nucl Magn Reson ; 25(1-3): 153-9, 2004 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-14698403

RESUMO

It has been recently recognized that residual intermolecular double-quantum coherences (iDQcs) provide a novel contrast mechanism to study heterogeneity in liquid systems. This is of much interest in the field of the physics of matter and biomedicine. Nowadays, literature concerning the behaviour of the iDQc signal originated by highly heterogeneous systems such as fluids in porous media is scarce. In this paper, we report and discuss our principal results about iDQc signal behaviour in confined liquid systems (trabecular bone, travertine, porous standard systems) and also some new results obtained on doped water in glass capillary pipes.


Assuntos
Fêmur/química , Vidro/química , Espectroscopia de Ressonância Magnética/métodos , Teste de Materiais/métodos , Modelos Químicos , Porosidade , Água/química , Adsorção , Animais , Ação Capilar , Bovinos , Humanos , Imagens de Fantasmas , Soluções/química
12.
Magn Reson Imaging ; 21(7): 799-804, 2003 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-14559345

RESUMO

The purpose of this paper is to investigate NMR applications to porous materials widely employed in artistic and historical monuments and largely studied in the Cultural Heritage conservation field. Carrara marble, Candoglia marble and travertine samples were studied and data from relaxation times measurements were compared. Very interesting results from treated samples are reported and explained under the structure related spin lattice relaxation time point of view. Images of Carrara marble aged sample (XIX century), coming from the Florence Cathedral obtained for short absorption time of water by capillary rise and for relatively small thickness slices together show the fluid's spatial distribution within the stone. Comparative images showing untreated sample with the treated ones were obtained suggesting very useful applications for the determination of treatment effectiveness.


Assuntos
Carbonatos , Materiais de Construção , Espectroscopia de Ressonância Magnética , Porosidade
13.
Magn Reson Imaging ; 21(3-4): 333-5, 2003.
Artigo em Inglês | MEDLINE | ID: mdl-12850728

RESUMO

Nuclear Magnetic Resonance was employed to obtain information on the pore filling during the absorption process. A porous carbonate stone, largely employed for buildings and mainly outdoor decorations was studied during water absorption by capillary rise, and filled pores radii were evaluated by comparison between experimental and theoretical parametric magnetization decay curves. Non mono-exponential T2 allowed spin populations to be split among the associated different relaxation times.


Assuntos
Carbonatos/química , Materiais de Construção , Espectroscopia de Ressonância Magnética/métodos , Absorção , Porosidade , Água
14.
Magn Reson Imaging ; 21(3-4): 413-4, 2003.
Artigo em Inglês | MEDLINE | ID: mdl-12850749

RESUMO

In heterogeneous systems the amplitude of the intermolecular double-quantum (DQ) signal depends on sample heterogeneity over a correlation distance dc=pi/(gammaGct). In this paper two different CRAZED-type sequences were applied in a porous medium phantom. One of these sequences gives rise to a DQ-T2 weighted signal, while the other one gives rise to a DQ-T2* weighted signal. Experimental results indicate that tuning of the correlation distance dc in a porous medium can alter the DQ signal in a manner which depends on the microstructure. This is evident only using the CRAZED-type sequence which gives rise to a DQ-T2* weighted signal.


Assuntos
Espectroscopia de Ressonância Magnética/métodos , Imagens de Fantasmas , Porosidade
15.
Neuroscience ; 118(1): 7-10, 2003.
Artigo em Inglês | MEDLINE | ID: mdl-12676131

RESUMO

The metabolic events of neuronal energetics during functional activity are still partially unexplained. In particular, lactate (and not glucose) was recently proposed as the main substrate for neurons during activity. By means of proton magnetic resonance spectroscopy, lactate was reported to increase during the first minutes of prolonged stimulation, but the studies reported thus far suffered from low temporal resolution. In the present study we used a time-resolved proton magnetic resonance spectroscopy strategy in order to analyse the evolution of lactate during the early seconds following a brief visual stimulation (event-related design). A significant decrease in lactate concentration was observed 5 s after the stimulation, while a recovering of the baseline was observed at 12 s.


Assuntos
Química Encefálica/fisiologia , Encéfalo/metabolismo , Regulação para Baixo/fisiologia , Metabolismo Energético/fisiologia , Potenciais Evocados Visuais/fisiologia , Ácido Láctico/metabolismo , Neurônios/metabolismo , Adulto , Humanos , Espectroscopia de Ressonância Magnética , Estimulação Luminosa , Tempo de Reação/fisiologia
16.
J Neurosci Res ; 71(4): 463-7, 2003 Feb 15.
Artigo em Inglês | MEDLINE | ID: mdl-12548701

RESUMO

The metabolic events underlying neuronal activity still remain the object of intense debate, in spite of the considerable amount of information provided from different experimental techniques. Indeed, several attempts at linking the cellular metabolic phenomena with the macroscopic physiological changes have not yet attained foolproof conclusions. The difficulties in drawing definitive conclusions are due primarily to the heterogeneity of the experimental procedures used in different laboratories, and also given the impossibility of extrapolating the findings obtained under stationary conditions (prolonged stimulation) to dynamic and transient phenomena. Recently, lactate has received much attention, following its proposal by Pellerin and Magistretti (1994; Proc. Natl. Acad. Sci. USA 91:10625-10629), instead of glucose, as the main substrate for neurons during activity. Several challenging aspects suggest the return to a more conventional view of neuronal metabolism, in which neurons are able to metabolize ambient glucose directly as their major substrate, also during activation.


Assuntos
Modelos Biológicos , Neurônios/metabolismo , Animais , Astrócitos/metabolismo , Glucose/metabolismo , Humanos
17.
Magn Reson Imaging ; 21(10): 1151-7, 2003 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-14725922

RESUMO

To study the sensitivity of intermolecular double quantum coherences (iDQc) imaging contrast to brain microstructure and brain anisotropy, we investigated the iDQC contrast between differently structured areas of the brain according to the strength and the direction of the applied correlation gradient. Thus diffusion-weighted imaging (DWI) and diffusion tensor imaging (DTI) maps have been obtained. This procedure, which consists of analyzing both iDQc and DWI images at different gradient strength and gradient direction, could be a promising tool for clinical brain investigations performed with higher than 1.5 T magnetic fields.


Assuntos
Encéfalo/anatomia & histologia , Imagem de Difusão por Ressonância Magnética , Anisotropia , Humanos
18.
Magn Reson Imaging ; 21(10): 1175-89, 2003 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-14725925

RESUMO

The purpose of this study was the development of a real-time filtering procedure of MRI artifacts in order to monitor the EEG activity during continuous EEG/fMRI acquisition. The development of a combined EEG and fMRI technique has increased in the past few years. Preliminary "spike-triggered" applications have been possible because in this method, EEG knowledge was only necessary to identify a trigger signal to start a delayed fMRI acquisition. In this way, the two methods were used together but in an interleaved manner. In real simultaneous applications, like event-related fMRI study, artifacts induced by MRI events on EEG traces represent a substantial obstacle for a right analysis. Up until now, the methods proposed to solve this problem are mainly based on procedures to remove post-processing artifacts without the possibility to control electrophysiological behavior of the patient during fMRI scan. Moreover, these methods are not characterized by a strong "prior knowledge" of the artifact, which is an imperative condition to avoid any loss of information on the physiological signals recovered after filtering. In this work, we present a new method to perform simultaneous EEG/fMRI study with real-time artifacts filtering characterized by a procedure based on a preliminary analytical study of EPI sequence parameters-related EEG-artifact shapes. Standard EEG equipment was modified in order to work properly during ultra-fast MRI acquisitions. Changes included: high-performance acquisition device; electrodes/cap/wires/cables materials and geometric design; shielding box for EEG signal receiver; optical fiber link; and software. The effects of the RF pulse and time-varying magnetic fields were minimized by using a correct head cap wires-locked environment montage and then removed during EEG/fMRI acquisition with a subtraction algorithm that takes in account the most significant EPI sequence parameters. The on-line method also allows a further post-processing utilization.


Assuntos
Artefatos , Eletroencefalografia , Imageamento por Ressonância Magnética , Processamento de Sinais Assistido por Computador , Algoritmos , Imagem Ecoplanar/métodos , Eletroencefalografia/métodos , Humanos , Imageamento por Ressonância Magnética/métodos
19.
Magn Reson Imaging ; 21(10): 1201-6, 2003 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-14725927

RESUMO

The aim of our work was to evaluate the feasibility of in vivo single-voxel quantitative proton MR spectroscopy in order to identify possible alterations in the main metabolite concentrations due to some metabolic dysfunctions in the cerebellum of patients suffering from a particular form of migraine called "with aura." Measurements of metabolite levels in the cerebellum disclosed reduced choline values (normalized both to N-acetyl-aspartate and creatine) in the patient group with respect to the age-matched control group. Our interest in this pathology is motivated by the fact that there are no available specific biochemical markers for migraine characterization, and the current diagnostic only takes advantage of the medical history and the clinical examination.


Assuntos
Ácido Aspártico/análogos & derivados , Cerebelo/metabolismo , Espectroscopia de Ressonância Magnética , Enxaqueca com Aura/diagnóstico , Prótons , Adulto , Ácido Aspártico/análise , Química Encefálica , Estudos de Casos e Controles , Colina/análise , Creatina/análise , Feminino , Humanos , Masculino
20.
Magn Reson Imaging ; 21(10): 1207-12, 2003 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-14725928

RESUMO

The purpose of this work was to investigate the relation between BOLD signal sign and transient vessels volume variation induced by apnea. This stimulus consisting of breath holding after inspiration is able to induce a light slowing down in venous blood flow like in a sort of Valsalva maneuver. We observed diffuse negative BOLD responding areas at cortical level and a stronger negative response in correspondence of the main sinuses. These phenomena seem to be unrelated to a specific neural activity, appearing to be expressions of a mechanical variation in the hemodynamics. Our study suggests that particular care must be considered in the interpretation of fMRI findings, especially when patients with vascular-related cerebral diseases are involved.


Assuntos
Encéfalo/fisiologia , Imageamento por Ressonância Magnética , Respiração , Adulto , Encéfalo/anatomia & histologia , Circulação Cerebrovascular , Humanos , Imageamento por Ressonância Magnética/métodos , Oxigênio/sangue
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