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J L Coatrieux

Publications and source records attributed to J L Coatrieux.

At least 19 recordsLinked to original sources
PubMed2005

A grand challenge for research: multimodal, multilevel and multiscale systems in medicine and biology.

Computational modelling, nano-bioscience and information technology in biology and medicine will play a major role in the interdisciplinary attempts to elucidate structures and functions of living systems. Developing tools capable to integrate the new advances and make benefit of them is crucial: accumulation of data and knowledge base with only storage and retrieval capabilities will have a poor impact if they are not made "active" or "operational". This is where models will play a central role in offering, not only sound ways for representation or simulation, but also the appropriate frames to put the players in the right place, with intra- and inter-level coupling and multisource handling. This paper advocated that sequential observations of multiple and complex mechanisms will be of limited interest to understand the inter-relations that are occurring at the same time, and therefore, that designing multimodal, multilevel and multiscale experiments, matched with these models, are of major importance.

Animals↗
PubMed2001

Fast detection and characterization of vessels in very large 3-D data sets using geometrical moments.

An improved and very fast algorithm dealing with the extraction of vessels in three-dimensional imaging is described. The approach is based on geometrical moments and a local cylindrical approximation. A robust estimation of vessel and background intensity levels, position, orientation, and diameter of the vessels with adaptive control of key parameters, is provided during vessel tracking. Experimental results are presented for lower limb arteries in multidetector computed tomography scanner.

Algorithms↗
PubMed2000

Towards dynamic cardiac scenes interpretation based on spatial-temporal knowledge.

Cardiac motion analysis enables to identify pathologies related to myocardial anomalies or coronary arteries circulation deficiencies. Conventionally, bi-dimensional (2D) left ventricle contour images have been extensively used, to perform quantitative measurements and qualitative evaluations of the cardiac function. Nevertheless, there are other cardiac anatomical structures, the coronary arteries, imaged on routine procedures, upon which complementary motion interpretation can be conducted. This paper presents an experimental methodology to perform dynamic cardiac scenes interpretation, studying three-dimensional (3D) coronary arteries spatial-temporal behavior. Being an alternative way to approach computer assisted cardiac motion interpretation, it reveals a wide range of rarely explored spatial-temporal situations and proposes how to address them. Considering the challenges to achieve dynamic scene interpretation, it is explained how spatial and temporal knowledge, are connected to specialist knowledge and measured parameters, to obtain a dynamic scene interpretation. Global and local motion features are modeled according to cardiac motion and geometrical knowledge, before its transformation into symbols. Anatomical knowledge and spatial-temporal knowledge are applied, along with spatial-temporal reasoning schemes, to access symbols meaning. Experimental results obtained using real data are presented. Complexity of interpretation envisioning is discussed, taking the given results as an example.

Artificial Intelligence↗
PubMed1999

Slice simulation from a model of the parenchymous vascularization to evaluate texture features: work in progress.

RATIONALE AND OBJECTIVES: To demonstrate the usefulness of a model of the parenchymous vascularization to evaluate texture analysis methods. METHODS: Slices with thickness varying from 1 to 4 mm were reformatted from a 3D vascular model corresponding to either normal tissue perfusion or local hypervascularization. Parameters of statistical methods were measured on 16128x128 regions of interest, and mean values and standard deviation were calculated. For each parameter, the performances (discrimination power and stability) were evaluated. RESULTS: Among 11 calculated statistical parameters, three (homogeneity, entropy, mean of gradients) were found to have a good discriminating power to differentiate normal perfusion from hypervascularization, but only the gradient mean was found to have a good stability with respect to the thickness. Five parameters (run percentage, run length distribution, long run emphasis, contrast, and gray level distribution) were found to have intermediate results. In the remaining three, curtosis and correlation was found to have little discrimination power, skewness none. CONCLUSION: This 3D vascular model, which allows the generation of various examples of vascular textures, is a powerful tool to assess the performance of texture analysis methods. This improves our knowledge of the methods and should contribute to their a priori choice when designing clinical studies.

Blood Vessels↗
PubMed1999

[The scientific bases of virtual endoscopy].

The recent advances in medical imaging, the avaibility of methods for image analysis and computer graphics, the technological resources provided by microdevices and the design of minimal access surgical procedures have open the road to new concepts. Virtual endoscopy represents one of these emerging areas and points out the applicative potential of three dimensional (3D) imaging. It leads to less invasive diagnosis and therapeutic achievements and provides important cues for education and interventional planning. Image segmentation, visualization, tissue modeling and interactions with surgical instruments are the fundamental components to build clinical applications. They are examined in this paper through 3D navigation systems, surgical simulations and image guided interventions.

Computer Simulation↗
PubMed1998

Three-dimensional reconstruction of the coronary arteries using a priori knowledge.

A method for 3D reconstruction of the coronary arteries from two radiographic images is presented. A novel technique for matching image structures is the main contribution of the work. After a comprehensive study of the knowledge required to approach this problem, an automatic method, which includes both numeric and symbolic procedures to solve geometric ambiguities, is developed. In the proposed method, all possible (virtual) reconstructions are first obtained. Their validity is evaluated by means of a priori knowledge about the 3D object and its projections. From the set of chosen possible solutions, the most likely solution is selected. The method is tested using real images and is implemented in a platform that allows further clinical validation.

Angiography, Digital Subtraction↗
PubMed1998

Analysis-synthesis of the phonocardiogram based on the matching pursuit method.

The matching pursuit method of Mallat and Zhang is applied to the analysis and synthesis of phonocardiograms (PCG's). The method is based on a classical Gabor wavelet or time-frequency atom which is the product of a sinusoid and a Gaussian window function. It decomposes a signal into a series of time-frequency atoms by an iterative process based on selecting the largest inner product of the signal (and the subsequent residues) with atoms from a redundant dictionary. The Gaussian window controls the envelope duration and time position of each atom; and the sinusoid represents the frequency. The method was applied to two sets of PCG's: one with very low-noise level and the other with 10% noise energy. Each data base includes 11 PCG's representing the normal and the pathological conditions of the heart. The normalized root-mean-square error (NRMSE) was computed between the original and the reconstructed signals. The results show that the matching pursuit method is very suitable to the transient and complex properties of the PCG's, as it yielded excellent NRMSE's around 2.2% for the two sets of 11 PCG's tested.

Heart Murmurs↗
PubMed1998

Time-frequency scaling transformation of the phonocardiogram based of the matching pursuit method.

A time-frequency scaling transformation based on the matching pursuit (MP) method is developed for the phonocardiogram (PCG). The MP method decomposes a signal into a series of time-frequency atoms by using an iterative process. The modification of the time scale of the PCG can be performed without perceptible change in its spectral characteristics. It is also possible to modify the frequency scale without changing the temporal properties. The technique has been tested on 11 PCG's containing heart sounds and different murmurs. A scaling/inverse-scaling procedure was used for quantitative evaluation of the scaling performance. Both the spectrogram and a MP-based Wigner distribution were used for visual comparison in the time-frequency domain. The results showed that the technique is suitable and effective for the time-frequency scale transformation of both the transient property of the heart sounds and the more complex random property of the murmurs. It is also shown that the effectiveness of the method is strongly related to the optimization of the parameters used for the decomposition of the signals.

Fourier Analysis↗
PubMed1998

Dynamic feature extraction of coronary artery motion using DSA image sequences.

This paper aims to define and describe features of the motion of coronary arteries in two and three dimensions, presented as geometrical parameters that identify motion patterns. The main left coronary artery centerlines, obtained from digital subtraction angiography (DSA) image sequences, are first reconstructed. Thereafter, global and local motion features are evaluated along the sequence. The global attributes are centerline and point trajectory lengths, displacement amplitude, and virtual reference point, while local attributes are displacement direction, perpendicular/radial components, rotation direction, and curvature and torsion. These kinetic features allow us to obtain a detailed quantitative description of the displacements of arteries' centerlines, as well as associated epicardium deformations. Our modeling of local attributes as quasi-homogeneous on a segment analysis, enables us to propose a novel numeric to symbolic image transformation, which provides the required facts for knowledge-based motion interpretation. Experimental results using real data are consistent with cardiac dynamic behavior.

Algorithms↗
PubMed1997

Time-domain quanification of amplitude, chemical shift, apparent relaxation time T2, and phase by wavelet-transform analysis. Application to biomedical magnetic resonance spectroscopy.

The wavelet-transform method is used to quantify the magnetic resonance spectroscopy (MRS) parameters: chemical shift, apparent relaxation time T2, resonance amplitude, and phase. Wavelet transformation is a time-frequency representation which separates each component from the FID, then successively quantifies it and subtracts it from the raw signal. Two iterative procedures have been developed. They have been combined with a nonlinear regression analysis method and tested on both simulated and real sets of biomedical MRS data selected with respect to the main problems usually encountered in quantifying biomedical MRS, specifically "chemical noise," resulting from overlapping resonances, and baseline distortion. The results indicate that the wavelet-transform method can provide efficient and accurate quantification of MRS data.

Algorithms↗
PubMed1997

A method to quantify invariant information in depth-recorded epileptic seizures.

In the field of epilepsy, the analysis of stereoelectroencephalographic (SEEG) signals recorded with depth electrodes provides major information on interactions between brain structures during seizures. A methodology of comparing SEEG seizure recordings is applied in 4 patients suffering from temporal lobe epilepsy. It proceeds in 3 steps: (i) segmentation of SEEG signals, (ii) characterization and labeling of segments and (iii) comparison of observations coded as sequences of symbol vectors. The third step is based on a vectorial extension of Wagner and Fischer's algorithm to first, quantify similarities between observations and second, extract invariant information, referred to as spatio-temporal signatures. These are automatically extracted by the algorithm without the need to make a priori assumptions on the 'patterns' to be searched for. Theoretical results show that two observations of non-equal duration can be matched by deforming the first one (using insertion/deletion operations on vectors) to optimally fit the second, under a minimal cost constraint. Clinical results show that the study brings objective results on reproducible mechanisms occurring during seizures: for a given patient, quantified descriptions of seizure periods are compared and similar ictal patterns, or signatures, are extracted from SEEG signals. Some of these signatures (particularly those containing spikes, spike-and-waves, slow waves and rapid discharges) are relevant: they seem to reflect reproducible propagation schemes whose analysis may help in the understanding of epileptogenic networks.

Electroencephalography↗
PubMed1997

Biomedical information technology: medicine and health care in the digital future.

Advancements in medicine and health care are being significantly influenced by the exploding information technology developments. The IEEE Transactions on Information Technology in Biomedicine will address the applications and the infrastructure innovations that would harness biomedical and health care programs in the 21st century.

Biomedical Engineering↗
PubMed1996

Extraction of spatio-temporal signatures from depth EEG seizure signals based on objective matching in warped vectorial observations.

In the field of epilepsy, the analysis of stereoelectroencephalographic (SEEG) signals recorded with depth electrodes provides major information on interactions between brain structures during seizures. A comprehensive methodology of comparing SEEG seizure recordings is presented. It proceeds in three steps: 1) segmentation of SEEG signals; 2) characterization and labeling of segments; and 3) comparison of observations coded as sequences of symbol vectors. The third step reports a vectorial extension of the Wagner and Fischer's algorithm to first, quantify similarities between observations and second, extract invariant sequences of events, referred to as spatiotemporal signatures. The study shows that two observations of nonequal duration can be matched by deforming the first one to optimally fit the second, under cost constraints. Results show that the methodology allows to exhibit signatures occurring during epileptic seizures and to point out different types of seizure patterns. The study brings objective results on reproducible interactions between brain structures during ictal periods and may help in the understanding of epileptogenic networks.

Algorithms↗
PubMed1995

[Analysis of texture in medical imaging. Review of the literature].

This paper presents a review of the applications of texture analysis in medical imaging. Many authors take a great interest in this topic (75 papers have been published since 1984) and try to elaborate automatic methods for tissue characterization. The results are not really convincing and applications are often reduced to feasibility studies. This failure is due to the empirical approach to the problem: the first studies were performed on ultrasound images, in which visual texture is very present, but no data standardization is available with this imaging modality. A more rational approach should provide better results. For each organ or tissue, it is necessary to find the appropriate source and texture analysis method. This difficult task requires reflection concerning the interactions between tissues and imaging sources, to define judicious structuring elements. These structuring elements should facilitate the choice of the best texture analysis method, for the particular application. Considerable methodological progress has yet to be made, after which texture analysis should be a useful and efficient tool for clinical use.

Humans↗
PubMed1994

Computer vision approaches for the three-dimensional reconstruction of coronary arteries: review and prospects.

The objective of this article is to define the different stages involved in the 3D reconstruction of arteries and to review, from our experience and from the literature, the solutions already proposed. A full reconstruction framework includes the characterization of the imaging device (in terms of distortion and calibration), the specificity of the image acquisition process, the preprocessing that can be applied, the detection of the vascular structures, the 2D feature formation, the reconstruction itself, and the visualization aspects. They are examined according to a computer vision approach where two or three views are assumed to be available. Their generalization to temporal image sequences are also considered. Some of the material reported here is unpublished. The article allows the reader to identify the true critical issues that are not often clearly mentioned in the literature and the challenges that they convey. A final discussion presents a few perspectives in this area of research.

Artificial Intelligence↗