Wissenschaftliche Studie, 2014
34 Seiten
1 INTRODUCTION
2 SELECTING THE REGION OF INTEREST
3 FEATURE EXTRACTION OF MEDICAL IMAGES
4 FEATURE CLASSIFICATION USING SVD
5 RESULTS AND DISCUSSION
This work aims to evaluate and compare the performance of Singular Value Decomposition (SVD) and Principle Component Analysis (PCA) classifiers in detecting abnormalities within Computer Tomography (CT) brain and skull images, focusing on efficiency and classification accuracy.
4.2. SINGULAR VALUE DECOMPOSITION (SVD)
A mathematical approach that directly reveals the rank and corresponding ideal basis of a dataset is the singular value decomposition (SVD). For a dataset in n dimensional space, for any k < n, the SVD will show the ideal basis for representing that data using only k dimensions [6]. If the SVD reveals that the dataset is full rank and no feature reduction is possible along the calculated axes, then no axes exist for which a reduction is possible. Furthermore, if no reduction is possible, this will be shown by the magnitudes of the singular values revealed by the SVD. An operation such as a classification that would be performed on the entire m × n matrix A can now be equivalently performed on the entire k × n matrix where k < m, resulting in a reduction in the number of bands present in each vector.
For practical purposes, singular values may in fact be nonzero yet be sufficiently close to zero to reduce the dimension of the data. The singular values ߪ,…,ߪrepresent distances from the subspace spanned by .,…,. and very small distances may not affect the operation that will be performed on the reduced data, such as classification. If none of the singular values on the diagonal are close to zero, then the data is already represented using as few dimensions as possible. Practically speaking, it would be necessary to think of a three dimensional (pixel row, pixel column, data bands) image in two dimensions in order to take advantage of the feature reduction made possible by using the SVD.
1 INTRODUCTION: This chapter provides the foundation for medical image processing, identifies the problem of automatic abnormality detection, and outlines the organizational structure of the research.
2 SELECTING THE REGION OF INTEREST: This section details the essential preprocessing stage of defining binary masks to isolate specific, relevant regions within brain CT images for further analysis.
3 FEATURE EXTRACTION OF MEDICAL IMAGES: This chapter explores techniques such as mean, variance, entropy, and wavelet approximation coefficients to transform input data into a compact feature set.
4 FEATURE CLASSIFICATION USING SVD: This section describes the implementation of SVD and PCA for binary classification, using predefined thresholds to distinguish between normal and abnormal medical images.
5 RESULTS AND DISCUSSION: This final chapter presents the experimental findings by applying performance metrics like sensitivity, specificity, and confusion matrices to assess the efficacy of the chosen classifiers.
Medical Image Processing, Computer Tomography, Feature Extraction, Singular Value Decomposition, SVD, Principle Component Analysis, PCA, Region of Interest, ROI, Abnormality Detection, Classifier Performance, Sensitivity, Specificity, F-Score, Wavelet Decomposition
The research focuses on developing and analyzing methods for the automatic detection of abnormalities in CT images of the brain and skull using machine learning classifiers.
The main themes include image preprocessing via ROI selection, dimensionality reduction through feature extraction, and the comparative performance of SVD and PCA classifiers.
The primary goal is to assess the performance of SVD and PCA in classifying medical images, specifically measuring their efficiency and accuracy in identifying abnormal tissue.
The study utilizes wavelet transforms for feature extraction and applies SVD and PCA as classification algorithms, evaluated through various statistical performance metrics.
The main sections cover image acquisition, ROI segmentation, extracting descriptive features like entropy and wavelet coefficients, and the execution of classification procedures.
The work is best characterized by terms such as medical image processing, feature extraction, SVD, PCA, and classification performance measures.
Selecting the correct region of interest improves the efficiency of subsequent stages by isolating the required regions and reducing unnecessary data for the classification algorithm.
The confusion matrix is used to visualize and compare classification results against ground truth, allowing for a clear understanding of the nature and frequency of classification errors.
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