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Biomedical subjects

Draulio B de Araujo

Publications and source records attributed to Draulio B de Araujo.

5 recordsLinked to original sources
PubMed2006

Language and motor FMRI activation in polymicrogyric cortex.

PURPOSE: To analyze the patterns of brain activation in polymicrogyric cortex in epilepsy patients by blood oxygenation level-dependent (BOLD) functional MRI (fMRI), during language and motor activation tasks. METHODS: Five patients with extratemporal epilepsy associated with polymicrogyria were scanned in a 1.5-T Siemens scanner with BOLD fMRI sequences, by following language and motor paradigms. Functional images were processed by using Brain Voyager software. RESULTS: Activation of polymicrogyric cortex in the brain area that corresponds to the motor strip was present in all patients. Language studies revealed activation of polymicrogyric cortex over Broca's area in three cases. CONCLUSIONS: Functionality was shown in polymicrogyric areas. Therefore if surgical resection is indicated, a careful functional planning is necessary because of functionality of the polymicrogyric cortex.

Adult↗
PubMed2006

Quantitative aspects of brain perfusion dynamic induced by BOLD fMRI.

The increase of relative cerebral blood flow (rCBF) may contribute for a change in blood oxygenation level dependent signal (BOLD). The main purpose of this study is to investigate some aspects of perfusional alterations in the human brain in response to a uniform stimulation: hypercapnia induced by breath holding. It was observed that the BOLD signal increased globally during hypercapnia and that it is correlated with the time of breath holding. This signal increase shows a clear distinction between gray and white matter, being greater in the grey matter.

Blood Flow Velocity↗
PubMed2005

Fetal source extraction from magnetocardiographic recordings by dependent component analysis.

Fetal magnetocardiography (fMCG) has been extensively reported in the literature as a non-invasive, prenatal technique that can be used to monitor various functions of the fetal heart. However, fMCG signals often have low signal-to-noise ratio (SNR) and are contaminated by strong interference from the mother's magnetocardiogram signal. A promising, efficient tool for extracting signals, even under low SNR conditions, is blind source separation (BSS), or independent component analysis (ICA). Herein we propose an algorithm based on a variation of ICA, where the signal of interest is extracted using a time delay obtained from an autocorrelation analysis. We model the system using autoregression, and identify the signal component of interest from the poles of the autocorrelation function. We show that the method is effective in removing the maternal signal, and is computationally efficient. We also compare our results to more established ICA methods, such as FastICA.

Algorithms↗
PubMed2005

Liver iron concentration evaluated by two magnetic methods: magnetic resonance imaging and magnetic susceptometry.

Quantification of liver iron concentration (LIC) is crucial in the management of patients suffering from certain pathologies that can produce iron overload, such as Cooley's anemia and hemochromatosis. All of these patients must control the level of iron deposits in their organs to avoid the toxicity of high LIC, which is potentially lethal. This paper describes experimental protocols for LIC measurement using two magnetic techniques: magnetic resonance imaging (MRI) and biomagnetic liver susceptometry (BLS). MRI proton transverse relaxation rate (R2) and image intensity, evaluated pixel by pixel, were used as indicators of iron load in the tissue. LIC measurement by BLS was performed using an AC superconducting susceptometer system. A group of 23 patients with a large range of iron overload (0.9 to 34.5 mgFe/g(dry tissue)) was evaluated with both techniques (MRI x BLS). A significant linear correlation (r = 0.89-0.95) was found between the LIC by MRI and by BLS. These results show the feasibility of using two noninvasive methodologies to evaluate liver iron store in a large concentration range. Both methodologies represent an equivalent precision.

Adolescent↗