Paul Suetens

Two-dimensional ultrasonic strain rate measurement of the human heart in vivo

A study is presented in which the feasibility of two-dimensional strain rate estimation of the human heart in vivo has been demonstrated. To do this, ultrasonic B-mode data were captured at a high temporal resolution of 3.8 ms and processed off-line. The motion of the RF signal patterns within the two-dimensional sector image was tracked and used as the basis for strain rate estimation. Both axial and lateral motion and strain rate estimates showed a good agreement with the results obtained by more established, one-dimensional techniques.

Knowledge-based system for the three-dimensional reconstruction of blood vessels from two angiographic projections

A knowledge-based system for the three-dimensional reconstruction of blood vessels from wide-angle coronary and stereoscopic cerebral angiographic projections is developed. For the reconstruction of the coronary vessels, the left coronary artery (LCA) is automatically labelled on standard RAO and LAO projections, using anatomical models of the LCA. The labelling system succeeds in giving the most important coronary arteries a correct anatomical label. These labelling results enable us to find corresponding segments in both images. In the case of the reconstruction of the cerebral vessels however, such an anatomical model is clearly unavailable. To find corresponding segments, small-angle projections must be relied on, resulting in very similar images. Owing to the small angular separation between both projections, the three-dimensional reconstruction will be less accurate. Once the corresponding segments in both projections are obtained, the three-dimensional artery trajectory is reconstructed with dynamic programming techniques. The three-dimensional reconstructed coronary vessels are also used for an automatic quantification of stenotic lesions.

A knowledge-based system for the delineation of blood vessels on subtraction angiograms

Abstract A new approach to outline blood vessels on angiograms is described, based on a generic blood vessel model and four models for determining segment intersections. These models are generic in the sense that they only rely on the angiographic imaging technique and on the geometrical and topological properties of blood vessels. The models do not depend on specific anatomical knowledge. As a consequence, they can be used as an initial segmentation step to outline the coronary, cerebral as well as the carotid vessels. Results on clinical cerebral subtraction angiograms are presented.

Chromosome Classification Using A Multi-layer Perceptron Neural Net

In this paper we present our recent study on using neural net systems for automated classification of human chromosomes. A multi-layer perceptron classifier was implemented and trained by a back-propagation algorithm. In comparison with traditional statistical pattern classification techniques, the neural net approach exhibits potential benefits of superior performance, adaptive learning capabilities, and high computation rates provided by massive parallelism. Results of the experiments carried out using both the perceptron and a Bayes classifier on a data set of chromosome feature measurements are given and compared.

A Knowledge-Based System For The 3D Reconstruction And Representation Of The Cerebral Blood Vessels From A Pair Of Stereoscopic Angiograms

This paper presents work in progress concerning an automatic system for the 3D reconstruction and representation of the cerebral vessels. It is based on a separate delineation of the blood vessels in two stereo images. First, we extract blood vessel segments from the image and subsequently we use those high level primitives to guide the stereoscopic matching process. Therefore, we make extensive use of domain specific knowledge like the orientation, thickness and intensity of blood vessels.

Knowledge-based 3-D segmentation of bloodvessels on a spatial sequence of MRI and Ultrasound images

We report on work in progress on segmentation and presentation of three-dimensional vascular morphology on 3D MR and Doppler Ultrasound angiograms. The segmentation strategy is twofold. First, we enhance blood-vessel-like structures using 3D non-linear filters. Second, these images can be directly displayed or used as input to medium-level processes. The medium-level filters are cast in the framework of energy minimization using deformable models.

A Knowledge-Based System For The Delineation Of The Coronary Arteries

In this article we will present work in progress concerning a knowledge-based system for the labeling of the coronary arteries on single projections. The approach is based on a gradual refinement of the interpretation results, starting from the detection of blood vessel center lines, the extraction of bar-like primitives and the connection into blood vessel segments. In this paper we will focus on the final stage which is the labeling of the delineated blood vessel segments. In contrast with most existing approaches which are mainly based on a sequential labeling of the vessels starting from the most important segment, our system uses a constraint satisfaction technique. Mainly, because most anatomical knowledge can be easily formalized as constraints on local attributes such as position, greyvalue, thickness and orientation and as constraints on relations between blood vessel segments such as left of or in same direction. Anatomical models are developed for the Left Coronary Artery in standard RAO and LAO views. In general, only 1-2 interpretations are left, which is an encouraging result if you take into account that for some projections there is a considerable overlap between vessel segments.

A 3-D Display System With Stereoscopic, Movement Parallax And Real-Time Rotation Capabilities

A 3-D display system which is based on the principle of active stereoparallax, has been developed. It consists of an IRIS-2400 graphics workstation, a Stereographics stereoscopic imaging system employing electro-optical shutters in glasses, and two Polhemus 3-D cursors, one in style form and one in block form. The usefulness of this system in general, and for medical imaging in particular, is discussed. The principle of active stereoparallax implies both stereoscopy and movement parallax. It gives the observer a reliable perception of space and allows him to make systematic distance estimates. Movement parallax is caused by coupling the observers movement to the resulting shifts of the objects in the image. In our system, this is realized by recording the observers head movement with the 3-D cursor in block form. It is shown that the interaction between the observer and the environment is important for space perception. The system has been developed in close cooperation with the Faculty of Industrial Design Engineering of the Delft University of Technology.

Critical Review Of Visual Inspection

Based on the literature as well as on theoretical knowledge and practical experience, the state of art of visual inspection is reviewed. First, the algorithmic and system aspects of this field are discussed. Second, a recent literature search for applications of visual inspection is briefly reviewed. Third, some future trends, expected advances and improvements needed to develop advanced vision systems are listed. Finally, conclusions are drawn from the previous discussion and the authors give their personal view of the actual situation and the future of visual inspection.

Three-dimensional reconstruction of the blood vessels of the brain

The possibility of three-dimensional recon-struction of the cerebral blood vessels has been investigated. In the first place, reconstruction from two orthogonal subtraction angiograms has been explored. Secondly, we have applied an automatic image matching algorithm to a stereo-pair of subtraction angiograms. A third approach - we term it computerized traditional tomography - uses the geometry of traditional tomography, but instead of radiographic film, a digital radiography device has to be used to store the projections.