Luiz Otavio Murta

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• Professor
• Professor (Associate) at University of São Paulo

Diffusion-weighted imaging (DWI) and diffusion tensor imaging (DTI) are well-known and powerful imaging techniques for MRI. Although DTI evaluation has evolved continually in recent years, there are still struggles regarding quantitative measurements that can benefit brain areas that are consistently difficult to measure via diffusion-based methods...

Accurately studying structural connectivity requires precise tract segmentation strategies. The U-Net network has been widely recognized for its exceptional capacity in image segmentation tasks and provides remarkable results in large tract segmentation when high-quality diffusion-weighted imaging (DWI) data are used. However, short tracts, which a...

Structural magnetic resonance imaging (MRI) data is essential for many neuroscience and clinical applications. The morphological features presented in the human brain are a rich source of information for understanding healthy development and pathological status, assisting the evaluation of brain atrophy, cortical thickness, and healthy brain aging....

Many studies in the last decades have correlated mandible bone structure with systemic diseases like osteoporosis. Mandible segmentation, as well as segmentation of other oral structures, is an essential step in studies that correlate oral structures' conditions with systemic diseases in general. However, manual mandible segmentation is a time-cons...

Transcranial magnetic stimulation (TMS) is a noninvasive technique of brain stimulation that has been widely used in both cognitive function studies and clinical applications. However, the biophysical mechanisms by which TMS activates cortical neurons and networks are still poorly understood. The present work aimed to create a computational model o...

OBJECTIVE: The main objective of this study was to evaluate intra- and inter-rater reliability in the analysis of digital images of donor areas for skin in burn patients using the CaPAS plugin in the ImageJ®. METHODS: Donor sites were reviewed by two independent reviewers in duplicate. The capture of images was standardized on the same device and...

Objective: Mutual information (MI) is consolidated as a robust similarity metric often used for medical image registration. Although MI provides a robust registration, it usually fails when the transform needed to register an image is too large due to MI local minima traps. This paper proposes and evaluates Generalized MI (GMI), using Tsallis entr...

Refractory epilepsy is a condition characterised by epileptic seizure occurrence, which cannot be controlled with antiepileptic drugs. Focal Cortical Dysplasia (FCD) was detected as one of the main causes of refractory epilepsy. Surgical intervention is necessary to minimise or eliminate seizure occurrences, although it is only indicated in cases w...

Multiscale entropy (MSE) analysis is a fundamental approach to access the complexity of a time series by estimating its information creation over a range of temporal scales. However, MSE may not be accurate or valid for short time series. This is why previous studies applied different kinds of algorithm derivations to short-term time series. Howeve...

PurposeIn neuroimage studies, it is usual to set a sequence of image preprocessing steps to obtain a controlled data analysis. One of the possible data preparation steps is the skull stripping, which removes non-brain tissues from the original image. Although the skull stripping procedure is time-consuming for manual assessments, most automatic app...

Purpose: It has been proven that early breast cancer diagnosis increases the success rate of treatment. Thus, annual mammography exam is recommended for women over forty which is relatively expensive, painful, and the safety of the used radiation dose is still debated. In this work, we introduced an automatic, low cost, and less painful exam to pre...

Among statistical models, Gaussian Mixture Models (GMMs) have been used in numerous applications to model the data in which a mixture of Gaussian curves fits them. Several methods have been introduced to estimate the optimum parameters to a GMM fitted to the data. The accuracy of such estimation methods is crucial to interpret the data. In this pap...

The prediction and detection of radiation-related caries (RRC) are crucial to manage the side effects of the head and the neck cancer (HNC) radiotherapy (RT). Despite the demands for the prediction of RRC, no study proposes and evaluates a prediction method. This study introduces a method based on artificial intelligence neural network to predict a...

Refractory epilepsy is a condition characterized by epileptic seizure occurrence which cannot be controlled with antiepileptic drugs. This condition is associated with an excessive neuronal discharge produced by a group of neurons in a certain epileptogenic zone. Focal Cortical Dysplasia (FCD), usually found in these zones, was detected as one of t...

Multiscale entropy (MSE) analysis is a fundamental approach to access the complexity of a time series by estimating its information creation over a range of temporal scales. However, MSE may not be accurate or valid for short time series. This is why previous studies applied different kinds of algorithm derivations to short-term time series. Howeve...

Purpose: Brain image volumetric measurements (BVM) methods have been used to quantify brain tissue volumes using magnetic resonance imaging (MRI) when investigating abnormalities. Although BVM methods are widely used, they need to be evaluated to quantify their reliability. Currently, the gold-standard reference to evaluate a BVM is usually manual...

We respond to comments placed on our original article with additional results showing the advantages of our method.

Image registration is a key operation in medical image processing, allowing a plethora of applications. Mutual information (MI) is consolidated as a robust similarity metric often used for medical image registration. Although MI provides a robust medical image registration, it usually fails when the needed image transform is too big due to MI local...

Twelve to 66% of patients with clinically non-functioning pituitary adenoma (NFPA) experience tumor recurrence 1–5 years after the first surgery. Nevertheless, there is still no recurrence prediction factor concisely established and reproduced in the literature for NFPA management. The present study evaluates the prognostic value of MRI Radiomics f...

Focal Cortical Dysplasia (FCD) is a type of brain injury that is the main cause of Refractory Epilepsy in children. Surgery is an alternative for the treatment of patients with FCD. However, the correct identification of the regions with FCD in the brain is necessary. The identification of FCD in Magnetic Resonance Images by using Convolutional Neu...

Focal cortical dysplasia (FCD) is a local malformation of the cortex, the main cause of refractory epilepsy in childhood and one of the most common causes in adults. The surgery decision and planning depend on the FCD localization. Although recent studies have successfully detected FCD through artificial intelligence, no study investigates the rele...

Displasia Cortical Focal (DCF) é um tipo de lesão cerebral que é a principal causa de Epilepsia Refratária em crianças. A cirurgia é uma alternativa para o tratamento de pacientes com DCF. No entanto, a identificação correta das regiões com DCF no cérebro é necessária. A identificação de DCF em Imagens de Ressonância Magnética usando Redes Neurais...

Twelve to 66% of patients with clinically non-functioning pituitary adenoma (NFPA) experience tumor recurrence 1–5 years after the first surgery. Nevertheless, there is still no recurrence prediction factor concisely established and reproduced in the literature for NFPA management. The present study evaluates the prognostic value of MRI Radiomics f...

The introduction of the multiscale entropy (MSE) method was a milestone in the field of complex physiological signal analysis. However, since MSE is inapplicable for short signals, several variants of MSE have been proposed. One of the most important variants of MSE is the modified multiscale entropy (MMSE), even though it can still produce biased...

Quantifying the intracranial tissue volume changes in magnetic resonance imaging (MRI) assists specialists to analyze the effects of natural or pathological changes. Since these changes can be subtle, the accuracy of the automatic compartmentalization method is always criticized by specialists. We propose and then evaluate an automatic segmentation...

This work describes a setup of the new acquisition system for 3D ultrasound images (i.e. B-mode) for breast tomography. Since premature and precise breast lesions diagnoses turn out in treatment more efficient and save lives, we are looking for a more precise, less painful exams and dose reduction for the patient. Therefore, a low cost scanner mech...

Mutual information (MI) is the standard method used in image registration and the most studied one but can diverge and produce wrong results when used in an automated manner. In this study we compared the results of the ITK Mattes MI function, used in 3D Slicer and ITK derived software solutions, and our own MICUDA Shannon and Tsallis MI functions...

Purpose In neurodegenerative clinical studies, patients are usually followed up for several years frequently examined in different MRI scanners and base magnetic fields. Technical specification differences in MRI scanners, e.g., acquisition protocols and spatial resolution, are two crucial limitations for longitudinal long-term cerebral atrophy inv...

Background: Multiple Sclerosis (MS) diagnosis and evaluation is often a challenging task due to its growing need for multimodal MRI acquisition protocol. Recently, the scientific community offers several computational alternatives to the time-consuming and subjective task of manual MS lesion segmentation. Although there is an increasing number of M...

Background: The relationship between microvasculopathy, autonomic denervation, and myocardial fibrosis, in Chagas cardiomyopathy is incompletely understood. The aim of this study was to explore the relative extent and anatomic distribution of myocardial hypoperfusion, autonomic denervation, and myocardial scarring using Single-Photon Emission Comp...

In microscopy, morphological characteristic of the axon are the most common features assessed in histological images of nerves. Although morphometric indexes are widely used to describe histological data, the calculation of those indexes is a highly time-consuming task that demands great manual effort from the specialist. Recently, two-dimensional...

Introduction: Severe burns benefit from skin grafting, and grafting surgery is of great importance in the treatment of these injuries. As a result, there is formation of an additional wound at the donor site, which is painful and susceptible to infection. However, the therapeutic approach to these problems at donor sites for skin grafting is insuf...

Complexity measures, defined as measures of irregularity over time scales, are the subject of a growing number of studies as the information they reveal can find utility in a large field of applications. One of the most popular complexity measures is the multiscale entropy. Nevertheless, more and more algorithms dedicated to complexity analyses are...

Quantifying complexity from heart rate variability (HRV) series is a challenging task, and multiscale entropy (MSE), along with its variants, has been demonstrated to be one of the most robust approaches to achieve this goal. Although physical training is known to be beneficial, there is little information about the long-term complexity changes ind...

Multiple Sclerosis (MS) is a chronic inflammatory disease of the central nervous system (CNS) which often requires a complex diagnosis procedure. Usually, MRI images are required in clinical routine, in which the MS lesions are constantly verified according to total volume, spatial localization and progression. However, the manual verification is t...

Doenças neurodegenerativas constituem hoje um campo de pesquisa de enorme demanda devido ao seu alto impacto socioeconômico. O uso de imagens por ressonância magnética (IRM) juntamente com avaliações clínicas constituem as bases da rotina de acompanhamento, diagnóstico e tomada de decisão clínica. Apesar de úteis, algumas modalidades de imagens est...

A Ressonância Magnética Cardíaca (Cardiac Magnetic Ressonance Imaging - Cardio-MRI) é uma das principais técnicas de imagens que permitem a detecção de lesões teciduais e análise da função ventricular. A delimitação do tecido miocárdico, envolto pelas bordas epicárdicas e endocárdicas, são fundamentais para uma melhor localização e quantificação de...

Methods 131 normal subjects were used to reconstruct a population-averaged template. After image pre processing, reconstruction and diagonalization, the eigenvalues and eigenvectors were used to reconstruct the quantitative DTI maps, namely fractional anisotropy (FA), mean diffusivity (MD), relative anisotropy (RA), and radial diffusivity (RD). The...

Heart rate variability (HRV) analysis is widely used to investigate the autonomic regulation of the cardiovascular system. HRV is often analyzed using RR time series, which can be affected by different types of artifacts. Although there are several artifact correction methods, there is no study that compares their performances in actual experimenta...

Methods A group of 20 healthy subjects with DTI data acquired (3T MR scanner) with different numbers of averages (N=1,2,4,6,8, and 16), where they were submitted to 2-D AAD and conventional anisotropic diffusion filters. The Relative Mean Error (RME), Structural Similarity Index (SSIM), Coefficient of Variation (CV) and tractography reconstruction...

Introdução: No tratamento de tumores de hipófise, observa-se uma série de possíveis desfechos para cada opção de tratamento associado a cada um dos tipos de tumor no espectro existente, o que torna o processo de tomada de decisões clínicas, e em alguns casos de diagnóstico, bastante complexo e dependente do tempo. Isso sugere uma constante busca po...

Reconstruction of the cortical surface is of great importance as a biomarker for many brain diseases, and in recent years a number of advances in image processing and analysis have been made in the cortical reconstruction process. However, despite the scientific community employing a range of advanced surface reconstruction algorithms in order to i...

Medical image registration plays an important role in determining topographic and morphological changes for functional diagnostic and therapeutic purposes. Manual alignment and semi-automated software still have been used; however they are subjective and make specialists spend precious time. Fully automated methods are faster and user-independent,...

Anisotropic and isotropic diffusion equations have been extensively applied on biomedical image processing for many years and a great diversity of algorithm have been proposed by the scientific community. Here, it is available a recent new implementation of the anomalous diffusion equation, based on the Fokker-Planck PDE diffusion equation (also kn...

Anisotropic and isotropic diffusion equations have been extensively applied on biomedical image processing for many years and a great diversity of algorithm have been proposed by the scientific community. Here, it is available a recent new implementation of the anomalous diffusion equation, based on the Fokker-Planck PDE diffusion equation (also kn...

Multiple sclerosis (MS) lesion segmentation has recently been intensively studied and improved. Usually, the lesion segmentation paradigm uses a set of structural images such as T1, T2, T2-FLAIR and PD, however, the normal-appearing white matter (NAWM) segmentation remains an open problem. Those traditional MRI structural images still lack sufficie...

Epileptic patients undergoing surgery in the temporal lobe usually present decline in cognitive functions associated to affected structures. In this study, we investigate a way of quantifying the tract loss using available software and tools by the use of Diffusion Tensor Images (DTI) and tractography methods. We hope this quantifying method will b...

Image texture analysis is a key task in computer vision. Although various methods have been applied to extract texture information, none of them are based on the principles of sample entropy, which is a measurement of entropy rate. This paper proposes a two-dimensional sample entropy method, namely SampEn2D, in order to measure irregularity in pixe...

The analysis of heart rate variability (HRV) by nonlinear methods has been gaining increasing interest due to their ability to quantify the complexity of cardiovascular regulation. In this study, multiscale entropy (MSE) and refined MSE (RMSE) were applied to track the complexity of HRV as a function of time scale in three pathological conscious an...

The analysis of heart rate variability (HRV) by nonlinear methods has been gaining increasing interest due to their ability to quantify the complexity of cardiovascular regulation. In this study, multiscale entropy (MSE) and refined MSE (RMSE) were applied to track the complexity of HRV as a function of time scale in three pathological conscious an...

Image texture analysis is a key task in computer vision. Although various methods have been applied to extract texture information, none of them are based on the principles of sample entropy, which is a measurement of entropy rate. This paper proposes a two-dimensional sample entropy method, namely SampEn 2D , in order to measure irregularity in pi...

The relationship between the myocardial tissue damage, myocardial perfusion defects and gaps in the auto-nomic innervation is still poorly understood. This paper proposes methods capable of providing an integrated visualization and analysis of tissue injuries through MRI images, autonomic innervations and myocardial perfusion through SPECT images....

Fetal magnetocardiograms (fMCGs) have been successfully processed with independent component analysis (ICA) to separate the fetal cardiac signals, but ICA effectiveness can be limited by signal nonstationarities due to fetal movements. We propose an ICA-based method to improve the quality of fetal signals separated from fMCG affected by fetal movem...

Diffusion process is widely applied to digital image enhancement both directly introducing diffusion equation as in anisotropic diffusion (AD) filter, and indirectly by convolution as in Gaussian filter. Anomalous diffusion process (ADP), given by a nonlinear relationship in diffusion equation and characterized by an anomalous parameters q , is sup...

Diffusion weighted imaging (DWI) and dif-fusion tensor imaging (DTI) are noisy submodalities images in magnetic resonance imaging (MRI) and usu-ally have long acquisition time due to repetitions needed to improve the signal noise ratio (SNR). Here we pro-pose and evaluate anisotropic anomalous diffusion (AAD) filter on DTI and DWI to enhance SNR an...

Resumo: A doença de Chagas é uma doença de importante relevância clínica, com alta incidência. A relação entre a lesão tecidual miocárdica e os defeitos na inervação autonômica na doença de Chagas é pouco conhecida. Este trabalho descreve o desenvolvimento e aplicação de métodos de análise de imagens capazes de prover uma análise integrada das lesõ...

Chagas disease is of major clinical relevance, with high incidence.The relation between the myocardial tis-sue damage, myocardial perfusion and defects in the au-tonomic innervations is poorly understood. This work pro-poses the development and application of image analy-sis methods capable of providing an integrated visualiza-tion and analysis of...

Cardiologic magnetic resonance imaging (MRI) has re-cently been improved by faster acquisition and higher res-olution hardware. Commercially available MRI equipment is able to capture contrast agents with the needed time and space definition to map myocardial viability. MRI my-ocardial imaging has an emerging role in cardiology stud-ies, and it has...

The visual appealing nature of the now popular BOLD fMRI may give the false impression of extreme simplicity, as if the the functional maps could be generated with the press of a single button. However, one can only get plausible maps after long and cautious processing, considering that time and noise come into play during acquisition. One of the m...

Relaxometry mapping is a quantitative modal-ity in magnetic resonance imaging (MRI) widely used in neuroscirence studies. Despite its relevance and utility, voxel measurement of relaxation time in relaxometry MRI is compro-mised by noise that is inherent to MRI modality and acquisition hardware. In order to enhance signal to noise ratio (SNR) and q...

Entropy analysis of images are usually performed using Shannon entropy, which calculates the probability of occurrency of each gray level on the image. However, not only the pixel gray level but also the spatial distribution of pixels might be important for image analysis. On the other hand, sample entropy (SampEn) is an important tool for estimati...

Neuroimage registration has an important role in clinical (for both diagnostic and therapeutic purposes) and research applications. In this article we describe the applicability of Tsallis Entropy as a new cost function for neuroimage registration through a comparative analysis based on the performance of the traditional approaches (correlation bas...

Multiple sclerosis (MS) is a degenerative neurological disease with increasing relevance. The segmentation of lesions on magnetic resonance imaging (MRI) and its boundary with healthy tissue remains a challenge for the diagnosis of patients with MS. Currently, various methods of MRI have been applied to this problem, but with modest success. In thi...

We tested the applicability of methods based on Detrended Fluctuation Analysis and HFO detection to the analysis of EEG signals from patients diagnosed with epilepsy, in order to test how efficient these methods would behave in a seizure prediction application. We were able to statistically distinguish the coefficients estimated in the pre-ictal pe...

http://jnm.snmjournals.org/content/55/supplement_1/2032.abstract?sid=e2e4c78e-35a3-402e-9c88-a6b8bfe980d1%5D

Resumo: A doença de Chagas é uma doença de importante relevância clínica, com alta incidência. Apesar do conhecimento de aspectos clínicos da doença de Chagas, a relação entre lesão tecidual miocárdica e os defeitos na inervação autonômica é pouco conhecida. Este artigo descreve o desenvolvimento e aplicação de métodos de análise de imagens capaz d...

The pre-surgical planning for patients with refractory epilepsy aim to the precise location of the Epileptogenic Zone (ZE), which must be surgically resected to rid the patient of the crises. Registration of Magnetic Resonance Imaging (MRI) and Single Photon Emission Computed Tomography (SPECT) plays relevant role in this procedure and fully automa...

A diminuição no tempo de aquisição em imagens por ressonância magnética (MRI – Magnetic Resonance Imaging), seja por tensor de difusão (DTI – Diffusion Tensor Imaging) ou outras modalidades de imagem, é um fator importante a ser estudado para a aplicação de um protocolo de imagem no ambiente clínico. Contudo, limitações relativas ao custo do aument...

Biomedical signals are very important reporters of the physiological status in human body. Therefore, great attention is devoted to the study of analysis methods that help extracting the greatest amount of relevant information from these signals. There are several free of charge softwares which can process biomedical data, but they are usually clos...

Noise is inherent to Diffusion-Weighted Magnetic Resonance Imaging (DWI) and noise reduction methods are necessary. Although process based on classical diffusion is one of the most used approaches for digital image, anomalous diffusion has the potential for image enhancement and it has not been tested for DWI noise reduction. This study evaluates A...

Spatial filtering is a ubiquitously used image processing approach to reduce noise, and frequently part of image processing pipelines. The most commonly used function is the Gaussian. Recently, a generalization of the Gaussian function consistent with nonadditive statistics was proposed. Although generalized Gaussian has been used for image filteri...

Background Prostate cancer is a serious public health problem that affects quality of life and has a significant mortality rate. The aim of the present study was to quantify the fractal dimension and Shannon’s entropy in the histological diagnosis of prostate cancer. Methods Thirty-four patients with prostate cancer aged 50 to 75 years having been...

This work combines symbolic machine learning and multiscale fractal techniques to generate models that characterize cellular rejection in myocardial biopsies and that can base a diagnosis support system. The models express the knowledge by the features threshold, fractal dimension, lacunarity, number of clusters, spatial percolation and percolation...

Complexity in time series is an intriguing feature of living dynamical systems, with potential use for identification of system state. Although various methods have been proposed for measuring physiologic complexity, uncorrelated time series are often assigned high values of complexity, errouneously classifying them as a complex physiological signa...

Noise is inherent to any image acquisition, therefore, exist many methods for noise reduction. Smoothing process based on isotropic diffusion is one of the most used approaches for digital image. Although classical diffusion covers a large class of process in nature, some interesting phenomenon can arise from anomalous diffusion. In this study, we...

Quantification of areas in myocardial infarction is a key factor to assess risk of ventricular arrhythmias and left ventricular dysfunction. This study proposes and evaluates the development of a system aimed to the segmentation of left ventricular myocardium and regions of infarction. The segmentation of the myocardium was performed using the tech...

We analyzed the effectiveness of linear short- and long-term variability time domain parameters, an index of sympatho-vagal balance (SDNN/RMSSD) and entropy in differentiating fetal heart rate patterns (fHRPs) on the fetal heart rate (fHR) series of 5, 3 and 2 min duration reconstructed from 46 fetal magnetocardiograms. Gestational age (GA) varied...

This paper analyses the electrical activity recorded in an experiment involving the maturation of dissociated embryonic hippocampal cultures, using Multielectrode Array (MEA) devices, starting from the moment of the culture’s placement in the device until its death, a period of 0 to 88 days in vitro (DIV). Classical “spike” analysis is applied to t...

Neuroimage registration has an important role in clinical (for both diagnostic and therapeutic purposes) and research applications. In this article we describe the applicability of Tsallis Entropy as a new cost function for neuroimage registration through a comparative analysis based on the performance of the traditional approaches (correlation bas...