Diffusion magnetic resonance imaging in multiple sclerosis.

Multiple sclerosis (MS) is considered the most common inflammatory autoimmune neurologic disorder and the most frequent cause of nontraumatic neurologic disability in young and middle-age adults. This article reviews the basic features of its magnetic resonance (MR) imaging lesions and, primarily, the use of diffusion MR imaging, which is increasingly applied to assess patients with MS, not only to investigate plaques but also the normal-appearing white matter, gray matter, optic nerve, and spinal cord, because of its ability to detect and quantify disease-related pathologic conditions of the central nervous system.

PET-RM neurológico com FDG-18F: ensaio iconográfico / Brain 18F-FDG PET-MRI coregistration: iconographic essay

A integração da tomografia por emissão de pósitrons (PET) com a ressonância magnética (RM) tem sido alvo de diversos estudos nos últimos anos. O PET é a modalidade de imagem mais sensível e específica na detecção de alterações metabólicas, entretanto, apresenta limitada resolução espacial. Por outro lado, a RM apresenta importante resolução espacial, além de avaliar estruturas com intensidade de sinal de partes moles com excelente contraste. O objetivo deste estudo é demonstrar, na forma de ensaio iconográfico, as potenciais aplicações clínicas da fusão de imagens de PET e RM. Os exames foram realizados em aparelho PET dedicado utilizando como radiofármaco a fluordeoxiglicose-18F (FDG) e corregistrados com RM de 1,5 T ou 3 T do encéfalo. A fusão por programa de imagens do cérebro tem acurácia já bem estabelecida. Consegue-se, assim, importante sinergia de um estudo funcional de PET com excelente detalhamento anatômico da RM. As aplicações clínicas mais atraentes dessa abordagem são a avaliação da zona epileptogênica em pacientes refratários ao tratamento medicamentoso, identificação dos pacientes com déficit cognitivo com maior risco de progressão para demência e distinção de demências e síndromes parkinsonianas.

The combination of positron emission tomography (PET) with magnetic resonance imaging (MRI) has been the subject of several studies in recent years. Positron emission tomography is the most sensitive and specific imaging modality in the detection of metabolic changes, but presents limited spatial resolution. On the other hand, MRI presents a significant spatial resolution, besides evaluating soft tissues signal intensity with excellent contrast resolution. The present iconographic essay is aimed at demonstrating the potential clinical application of PET/MRI coregistration. The studies were performed in a dedicated PET unit with 18F-fluorodeoxyglucose (FDG) as radiopharmaceutical and coregistered with 1.5 T or 3 T brain MRI. The brain images fusion software presents an already well-established accuracy, so a significant synergy between a functional PET study and an excellent MRI anatomical detail is achieved. The most attractive clinical applications of this approach are the following: epileptogenic zone assessment in patients refractory to drug therapy, identification of patients with cognitive impairment at higher risk for progression to dementia and differentiation of dementias and Parkinsonian syndromes.

Potential role of diffusion tensor MRI in the differential diagnosis of mild cognitive impairment and Alzheimer's disease.

OBJECTIVE: The purpose of this study was to evaluate the fractional anisotropy values of several white matter tracts with the aim of differentiating a healthy population from persons with mild cognitive impairment or Alzheimer's disease. SUBJECTS AND METHODS: Seventy-nine patients with memory impairment and 16 volunteer controls participated in the study. MRI was performed with a 1.5-T system. Conventional MR images and diffusion tensor images were obtained for all participants. The diffusion tensor imaging data were postprocessed, and low b-value, fractional anisotropy, and fractional anisotropy color-coded maps were calculated. With the three maps as an anatomic reference, fractional anisotropy was measured for hippocampal formations, superior longitudinal fascicles, posterior cingulate gyri, and the splenium of the corpus callosum. Kruskal-Wallis and Steel-type multiple-comparison nonparametric tests were performed for the statistical analysis. RESULTS: The fractional anisotropy values for the splenium of the corpus callosum, bilateral posterior cingulate gyri, and bilateral superior longitudinal fascicles of patients with mild cognitive impairment and those with probable Alzheimer's disease were significantly lower than the values of controls. No differences were found in hippocampal formations in any group. No significant difference was found in fractional anisotropy values in comparisons of mild cognitive impairment versus possible Alzheimer's disease and probable Alzheimer's disease or comparisons of probable Alzheimer's disease and possible Alzheimer's disease. CONCLUSION: Diffusion tensor imaging is a promising technique for the evaluation of patients with probable mild cognitive impairment. Early detection of the disease expands the treatment options, increasing the likelihood of a good clinical response and enhancing the quality of life of patients and their relatives. Further studies with larger populations are needed to confirm the role of diffusion tensor imaging in the evaluation of memory impairment.

Evaluation of white matter in patients with multiple sclerosis through diffusion tensor magnetic resonance imaging.

OBJECTIVE: To study the white matter of patients with multiple sclerosis (MS) with diffusion tensor magnetic resonance (MR) imaging (DTI). METHOD: Forty patients with clinical-laboratorial diagnosis of relapsing-remitting MS and 40 age- and sex-matched controls, who underwent conventional and functional (DTI) MR imaging, were included in the study. The DTI sequences resulted in maps of fractional anisotropy (FA) and regions of interest were placed on the plaques, peri-plaque regions, normal-appearing white matter (NAWM) around the plaques, contralateral normal white matter (CNWM) and normal white matter of the controls (WMC). The FA values were compared and the statistical treatment was performed with the Mann-Whitney U test. RESULTS: The mean FA in plaques was 0.268, in peri-plaque regions 0.365, in NAWM 0.509, in CNWM 0.552 and in WMC 0.573. Statistical significant differences in FA values were observed in plaques, peri-plaque regions and in NAWM around the plaques when compared to the white matter in the control group. There was no significant difference between the FA values of the CNWM of patients with MS and normal white matter of controls. CONCLUSION: Patients with MS show difference in the FA values of the plaques, peri-plaques and NAWM around the plaques when compared to the normal white matter of controls. As a result, DTI may be considered more efficient than conventional MR imaging for the study of patients with MS.

Evaluation of white matter in patients with multiple sclerosis through diffusion tensor magnetic resonance imaging

OBJECTIVE: To study the white matter of patients with multiple sclerosis (MS) with diffusion tensor magnetic resonance (MR) imaging (DTI). METHOD: Forty patients with clinical-laboratorial diagnosis of relapsing-remitting MS and 40 age- and sex-matched controls, who underwent conventional and functional (DTI) MR imaging, were included in the study. The DTI sequences resulted in maps of fractional anisotropy (FA) and regions of interest were placed on the plaques, peri-plaque regions, normal-appearing white matter (NAWM) around the plaques, contralateral normal white matter (CNWM) and normal white matter of the controls (WMC). The FA values were compared and the statistical treatment was performed with the Mann-Whitney U test. RESULTS: The mean FA in plaques was 0.268, in peri-plaque regions 0.365, in NAWM 0.509, in CNWM 0.552 and in WMC 0.573. Statistical significant differences in FA values were observed in plaques, peri-plaque regions and in NAWM around the plaques when compared to the white matter in the control group. There was no significant difference between the FA values of the CNWM of patients with MS and normal white matter of controls. CONCLUSION: Patients with MS show difference in the FA values of the plaques, peri-plaques and NAWM around the plaques when compared to the normal white matter of controls. As a result, DTI may be considered more efficient than conventional MR imaging for the study of patients with MS.

OBJETIVO: Estudar a substância branca de pacientes com esclerose múltipla (EM) através de imagens de ressonância magnética (RM) por tensor de difusão (DTI). MÉTODO: Foram avaliados 40 pacientes com diagnóstico clínico-laboratorial de EM remitente-recorrente e quarenta controles pareados por idade e sexo, os quais foram submetidos à RM convencional e funcional (DTI). As seqüências de DTI resultaram em mapas de anisotropia fracionada (FA) e as regiões de interesse foram posicionadas nas placas, regiões peri-placas, substância branca aparentemente normal (SBAN) ao redor das placas, substância branca normal contra-lateral (SBNC) e substância branca normal do grupo controle (SBC). Os valores de FA foram comparados e a análise estatística foi realizada utilizando o teste Mann-Whitney U. RESULTADOS: A média de FA nas placas foi 0,268, nas regiões peri-placas 0,365, na SBAN 0,509, na SBNC 0,552 e na SBC 0,573. Foram observadas diferenças estatisticamente significativas nos valores de FA nas placas, regiões peri-placas e na SBAN ao redor das placas quando comparados com a SBC. Não houve diferença entre os valores de FA na SBNC dos pacientes com EM e na SBC. CONCLUSÃO: Pacientes com EM demonstram diferença nos valores de FA nas placas, peri-placas e SBAN ao redor das placas quando comparados com a SBC. Assim, o DTI pode ser considerado mais eficiente do que as seqüências de ressonância magnética convencional no estudo dos pacientes com EM.