465 research outputs found
Evaluation of machine learning algorithms and structural features for optimal MRI-based diagnostic prediction in psychosis
A relatively large number of studies have investigated the power of structural magnetic resonance imaging (sMRI) data to discriminate patients with schizophrenia from healthy controls. However, very few of them have also included patients with bipolar disorder, allowing the clinically relevant discrimination between both psychotic diagnostics. To assess the efficacy of sMRI data for diagnostic prediction in psychosis we objectively evaluated the discriminative power of a wide range of commonly used machine learning algorithms (ridge, lasso, elastic net and L0 norm regularized logistic regressions, a support vector classifier, regularized discriminant analysis, random forests and a Gaussian process classifier) on main sMRI features including grey and white matter voxel-based morphometry (VBM), vertex-based cortical thickness and volume, region of interest volumetric measures and wavelet-based morphometry (WBM) maps. All possible combinations of algorithms and data features were considered in pairwise classifications of matched samples of healthy controls (N = 127), patients with schizophrenia (N = 128) and patients with bipolar disorder (N = 128). Results show that the selection of feature type is important, with grey matter VBM (without data reduction) delivering the best diagnostic prediction rates (averaging over classifiers: schizophrenia vs. healthy 75%, bipolar disorder vs. healthy 63% and schizophrenia vs. bipolar disorder 62%) whereas algorithms usually yielded very similar results. Indeed, those grey matter VBM accuracy rates were not even improved by combining all feature types in a single prediction model. Further multi-class classifications considering the three groups simultaneously made evident a lack of predictive power for the bipolar group, probably due to its intermediate anatomical features, located between those observed in healthy controls and those found in patients with schizophrenia. Finally, we provide MRIPredict (https://www.nitrc.org/projects/mripredict/), a free tool for SPM, FSL and R, to easily carry out voxelwise predictions based on VBM images
Underwater image restoration: super-resolution and deblurring via sparse representation and denoising by means of marine snow removal
Underwater imaging has been widely used as a tool in many fields, however, a major issue is the quality of the resulting images/videos. Due to the light's interaction with water and its constituents, the acquired underwater images/videos often suffer from a significant amount of scatter (blur, haze) and noise. In the light of these issues, this thesis considers problems of low-resolution, blurred and noisy underwater images and proposes several approaches to improve the quality of such images/video frames.
Quantitative and qualitative experiments validate the success of proposed algorithms
Robust Brain MRI Image Classification with SIBOW-SVM
The majority of primary Central Nervous System (CNS) tumors in the brain are
among the most aggressive diseases affecting humans. Early detection of brain
tumor types, whether benign or malignant, glial or non-glial, is critical for
cancer prevention and treatment, ultimately improving human life expectancy.
Magnetic Resonance Imaging (MRI) stands as the most effective technique to
detect brain tumors by generating comprehensive brain images through scans.
However, human examination can be error-prone and inefficient due to the
complexity, size, and location variability of brain tumors. Recently, automated
classification techniques using machine learning (ML) methods, such as
Convolutional Neural Network (CNN), have demonstrated significantly higher
accuracy than manual screening, while maintaining low computational costs.
Nonetheless, deep learning-based image classification methods, including CNN,
face challenges in estimating class probabilities without proper model
calibration. In this paper, we propose a novel brain tumor image classification
method, called SIBOW-SVM, which integrates the Bag-of-Features (BoF) model with
SIFT feature extraction and weighted Support Vector Machines (wSVMs). This new
approach effectively captures hidden image features, enabling the
differentiation of various tumor types and accurate label predictions.
Additionally, the SIBOW-SVM is able to estimate the probabilities of images
belonging to each class, thereby providing high-confidence classification
decisions. We have also developed scalable and parallelable algorithms to
facilitate the practical implementation of SIBOW-SVM for massive images. As a
benchmark, we apply the SIBOW-SVM to a public data set of brain tumor MRI
images containing four classes: glioma, meningioma, pituitary, and normal. Our
results show that the new method outperforms state-of-the-art methods,
including CNN
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