PubMed Health⌕ Search

Biomedical subjects

A N Venetsanopoulos

Publications and source records attributed to A N Venetsanopoulos.

6 recordsLinked to original sources

Ensemble-based discriminant learning with boosting for face recognition.

In this paper, we propose a novel ensemble-based approach to boost performance of traditional Linear Discriminant Analysis (LDA)-based methods used in face recognition. The ensemble-based approach is based on the recently emerged technique known as "boosting". However, it is generally believed that boosting-like learning rules are not suited to a strong and stable learner such as LDA. To break the limitation, a novel weakness analysis theory is developed here. The theory attempts to boost a strong learner by increasing the diversity between the classifiers created by the learner, at the expense of decreasing their margins, so as to achieve a tradeoff suggested by recent boosting studies for a low generalization error. In addition, a novel distribution accounting for the pairwise class discriminant information is introduced for effective interaction between the booster and the LDA-based learner. The integration of all these methodologies proposed here leads to the novel ensemble-based discriminant learning approach, capable of taking advantage of both the boosting and LDA techniques. Promising experimental results obtained on various difficult face recognition scenarios demonstrate the effectiveness of the proposed approach. We believe that this work is especially beneficial in extending the boosting framework to accommodate general (strong/weak) learners.

Algorithms↗

Application of active contours for photochromic tracer flow extraction.

This paper addresses the implementation of image processing and computer vision techniques to automate tracer flow extraction in images obtained by the photochromic dye technique. This task is important in modeled arterial blood flow studies. Currently, it is performed via manual application of B-spline curve fitting. However, this is a tedious and error-prone procedure and its results are nonreproducible. In the proposed approach, active contours, snakes, are employed in a new curve-fitting method for tracer flow extraction in photochromic images. An algorithm implementing snakes is introduced to automate extraction. Utilizing correlation matching, the algorithm quickly locates and localizes all flow traces in the images. The feasibility of the method for tracer flow extraction is demonstrated. Moreover, results regarding the automation algorithm are presented showing its accuracy and effectiveness. The proposed approach for tracer flow extraction has potential for real-system application.

Algorithms↗

On the training and performance of high-order neural networks.

An extensive study was undertaken on the architecture, training, and properties of neural networks of order higher than 1. The formulation of the training of high-order neural networks as a nonlinear associative recall problem provides the basis for their optimal least squares training. The simplicity of the outer-product rule motivates the study of the approximation of optimal least squares training by the outer-product rule and the effect of the network order on the efficiency of this approximation. Neural networks with composite key patterns are subsequently proposed as the natural generalization of neural networks of order higher than 1. The properties of this class of neural networks are revealed by studying their optimal least squares training and its relationship with the outer-product rule. The performance of neural networks with composite key patterns is analytically evaluated by studying their capacity. The properties and performance bounds provided by the analytical study are verified through experimental results.

Least-Squares Analysis↗

On the performance of single-layered neural networks.

This paper studies the performance of single-layered neural networks. This study begins with the performance of single-layered neural networks trained using the outer-product rule. The outer-product rule is a suboptimal learning scheme, resulting under certain assumptions from optimal least-squares training of single-layered neural networks with respect to their analog output. Extensive analysis reveals the improvement on the network performance caused by its optimal least-squares training. The effect of the training scheme on the performance of single-layered neural networks with binary output is exhibited by experimentally comparing the performance of single-layered neural networks trained with respect to their analog and binary output.

Mathematics↗

Knowledge-based landmarking of cephalograms.

Orthodontists have defined a certain number of characteristic points, or landmarks, on X-ray images of the human skull which are used to study growth or as a diagnostic aid. This work presents the first step toward an automatic extraction of these points. They are defined with respect to particular lines which are retrieved first. The original image is preprocessed with a prefiltering operator (median filter) followed by an edge detector (Mero-Vassy operator). A knowledge-based line-following algorithm is subsequently applied, involving a production system with organized sets of rules and a simple interpreter. The a priori knowledge implemented in the algorithm must take into account the fact that the lines represent biological shapes and can vary considerably from one patient to the next. The performance of the algorithm is judged with the help of objective quality criteria. Determination of the exact shapes of the lines allows the computation of the positions of the landmarks.

Artificial Intelligence↗

Modelling and restoration of ultrasonic phased-array B-scan images.

A model is presented for the radio-frequency image produced by a B-scan (pulse-echo) ultrasound imaging system using a phased-array transducer. This type of scanner is widely used for real-time heart imaging. The model allows for dynamic focusing as well as an acoustic lens focusing the beam in the elevation plane. A result of the model is an expression to compute the space-variant point spread function (PSF) of the system. This is made possible by the use of a combination of Fresnel and Fraunhoffer approximations which are valid in the range of interest for practical applications. The PSF is used to design restoration filters in order to improve image resolution. The filters are then applied to experimental images of wires.

Mathematics↗