Oswaldo Baffa Filho

A numerical study of the Kullback-Leibler distance in functional magnetic resonance imaging

The Kullback-Leibler distance (or relative entropy) is applied in the analysis of functional magnetic resonance (fMRI) data series. Our study is designed for event-related (ER) experiments, where a brief stimulus is presented and a long period of rest is followed. In particular, this relative entropy is used as a measure of the distance between the probability distributions p1 and p2 of the signal levels related to stimulus and non-stimulus. In order to avoid undesirable divergences of the Kullback-Leibler distance, a small positive parameter d is introduced in the definition of the probability functions in such a way that it does not bias the comparison between both distributions. Numerical simulations are performed so as to determine the probability densities of the mean Kullback-Leibler distance

Inter-institutional protocol describing the use of three-dimensional printing for surgical planning in a patient with childhood epilepsy: From 3D modeling to neuronavigation

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Correlation between antioxidant activity and coffee beverage quality by Electron Spin Resonance Spectroscopic

(throughout the N epochs of the whole experiment). For small values of N (N < 30), such probability densities

Performance quantification of clustering algorithms for false positive removal in fMRI by ROC curves

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Stomach emptying evaluation by ultrasound and susceptometric measurements with a hybrid transducer

are found to be fitted very well by Gamma distributions (c2 < 0.0009). The sensitivity and specificity of the method are evaluated by construction of the receiver operating characteristic (ROC) curves for some values of signal-to-noise ratio (SNR). The functional maps corresponding to real data series from an asymptomatic volunteer submitted to an ER motor stimulus is obtained by using the proposed technique. The maps present activation in primary and secondary motor brain areas. Both simulated and real data analyses indicate that the relative entropy can be useful for fMRI analysis in the information measure scenario.

Some Evidence of a Date of First Humans to Arrive in Brazil

This study is the first step in an effort to develop three-dimensional (3D) printing for use in pediatric surgical planning. In order to accomplish this, we established an effective collaboration between Ribeirao Preto Clinics Hospital (HCRP) and Renato Archer Center for Information Technology (CTI). Printed biomodels can be used to support discussions, decision-making, and neuronavigation before surgery. The main purpose of 3D printing for specific case handling is to reduce damage by enhancing knowledge of orientation during surgical planning and personnel training before surgery. Here, we produced an object that represented the brain and face segment of a patient via additive manufacturing technology based on magnetic resonance imaging (MRI) data. Specific landmarks were measured by three distinct methods: manual caliper, an InVesalius software measurement tool, and neuronavigation coordinate detection. The mean coefficient of variation was 7.17% between all methods and landmarks measured. Our results validate the combined use of biomodels with InVesalius software tools for the assessment of individual brain anatomy facilitating manual handling and visualization of 3D models. The establishment of communication protocols between the teams involved, as well as navigation protocols for quality control, presents the possibility of developing long term training programs, and promotes the congregation of individuals from research areas in Medical Physics, Medical Sciences, and Neuroscience.

Análise dos resultados do programa de gerenciamento da qualidade dos equipamentos radiológicos

Brazil is the largest producer of coffee in the world and coffee prices are directly linked to grain quality. In this work, the antioxidant activity of coffee was related to its quality through Electron Spin Resonance Spectroscopy (ESR), as an attempt to establish a non-subjective method to classify the grain quality. For that purpose, the IC50 and temporal monitoring of its non-oxidized fraction were determined for three bean qualities: Soft (High), Hard (Medium) and Rio (Low). Methanolic solution of 2,2-difenil-1-picril-hidrazila (DPPH), that has a stable radical and a JEOL FA-200 (X-Band) spectrometer were used for these tests. The temporal monitoring of reaction between radical and coffee was performed. The rate of reduced or of antioxidated radicals was determined on time and for each coffee beverage quality were found different slopes of curve: Soft (0.32±0.02), Hard (0.47±0.02) and Rio (0.60±0.02). The IC50 result of Rio quality (2.7 ± 0.9) was different from the Soft (7.8 ± 1.9) and Hard (6.5 ± 1.5) values, but there was no difference between the High and Medium results due to the uncertainty associated. Therefore the results found, mainly for monitoring temporal, establish a new quantitative methodology for classifying the coffee beverage quality.

Estudo da funçäo de mistura do alimento no estômago avaliado por técnica biomagnética

Introduction: nFunctional magnetic resonance imaging (fMRI) is a non-invasive technique that allows the detection of specific cerebral functions in humans based on hemodynamic changes. The contrast changes are about 5%, making visual inspection impossible. Thus, statistic strategies are applied to infer which brain region is engaged in a task. However, the traditional methods like general linear model and cross-correlation utilize voxel-wise calculation, introducing a lot of false-positive data. So, in this work we tested post-processing cluster algorithms to diminish the false-positives. n nMethods: nIn this study, three clustering algorithms (the hierarchical cluster, k-means and self-organizing maps) were tested and compared for false-positive removal in the post-processing of cross-correlation analyses. n nResults: nOur results showed that the hierarchical cluster presented the best performance to remove the false positives in fMRI, being 2.3 times more accurate than k-means, and 1.9 times more accurate than self-organizing maps. n nConclusion: nThe hierarchical cluster presented the best performance in false-positive removal because it uses the inconsistency coefficient threshold, while k-means and self-organizing maps utilize a priori cluster number (centroids and neurons number); thus, the hierarchical cluster avoids clustering scattered voxels, as the inconsistency coefficient threshold allows only the voxels to be clustered that are at a minimum distance to some cluster.

Banco de dados relacional para tomografia por ressonância magnética nuclear

Gastric emptying reflects a diversity of important physiological functions. Alternating Current Biosusceptometry (ACB) is an inexpensive, radiation-free, and noninvasive method to evaluate gastric emptying, but its response depends on the spatial distribution of the magnetized material and does not have anatomical information. The hybrid transducer - which combines ACB and ultrasound probe - improved susceptometric measurements potential, namely the spatial localization of the magnetized source. This study monitored relative stomach emptying in rats with the aid of the hybrid transducer. Yogurt mixed with ferrite particles was injected into the rats stomach. The hybrid transducer was placed on the rats abdominal during experiments. Susceptometric signal and power Doppler (PWD) data were saved and post-processed. In a second experiment, a volumetric image from axial sequences was obtained by means of a transducer displacement system. The relative stomach emptying was evaluated on the bases of PWD images and the susceptometric signal with the hybrid transducer. PWD maps highlighted the movement of magnetic particles (due magnetic force from ACB excitation coils) and showed the rats stomach location with anatomic information (B-mode). After the acquisition period, the mean relative ACB signal decayed by 4.6 ± 0.1%, and the mean relative PWD area decreased by 4.5 ± 0.2% as a result of stomach emptying. However, these values diminished (∼ 0.5%) when stomach shape was larger and the meal was more widely spread. The distribution spatial was more sensitive to PWD than ACB. The PWD volumetric image provided details of the stomach wall, which may enable minimally invasive detestation of abnormalities. Ultrasound image increased ACB spatial resolution and furnished additional anatomical information.