Biomedical subjects

M G Strintzis

Publications and source records attributed to M G Strintzis.

13 recordsLinked to original sources

PubMed2000

Deformable boundary detection of stents in angiographic images.

In this paper, a procedure is described for deformable boundary detection of medical tools, called stents, in angiographic images. A stent is a surgical stainless steel coil that is placed in the artery in order to improve blood circulation in regions where a stenosis has appeared. Assuming initially a set of three-dimensional (3-D) models of stents and using perspective projection of various deformations of the 3-D model of the stent, a large set of synthetic two-dimensional (2-D) images of stents is constructed. These synthetic images are then used as a training set for deriving a multivariate Gaussian density estimate based on eigenspace decomposition and formulating a maximum-likelihood estimation framework in order to reach an initial rough estimate for automatic object recognition. The silhouette of the detected stent is then refined by using a 2-D active contour (snake) algorithm integrated with a novel iterative initialization technique, which takes into consideration the geometry of the stent. The algorithm is experimentally evaluated using real angiographic images containing stents.

Algorithms↗

PubMed2000

'LipTelephone' a videophone for the deaf.

This paper describes the 'LipTelephone' system, which is being developed under a Greek AMEA research project, with the purpose to serve as a videophone that can also be used by lip readers. This system aims to combine model-based with traditional coding techniques in order to exploit the information redundancy in a scene of known content, while achieving high fidelity representation in the specific area of interest, which is the speaker's mouth. The recent MPEG-4 coding standard provides the framework, which is employed, for these purposes.

Communication Devices for People with Disabilities↗

PubMed2000

Deformable boundary detection of stents in angiographic images.

In this paper a procedure is described for deformable boundary detection of medical tools, called stents, in angiographic images. A stent is a surgical stainless steel coil which is placed in the artery in order to improve blood circulation, in regions where a stenosis has appeared. Assuming initially a set of 3-D models of stents and using perspective projection of various deformations of the 3-D model of the stent, a large set of synthetic 2D images of stents is constructed. These synthetic images are then used as a training set for deriving a multivariate Gaussian density estimate based on eigenspace decomposition and formulating a Maximum-Likelihood estimation framework in order to reach an initial rough estimate for automatic object recognition. The silhouette of the detected stent is then refined by using a 2D active contour (snake) algorithm integrated with a novel iterative initialization technique which takes into consideration the geometry of the stent. The algorithm is experimentally evaluated using real angiographic images containing stents.

Algorithms↗

PubMed1999

Tracking the left ventricle in echocardiographic images by learning heart dynamics.

In this paper a temporal learning-filtering procedure is applied to refine the left ventricle (LV) boundary detected by an active-contour model. Instead of making prior assumptions about the LV shape or its motion, this information is incrementally gathered directly from the images and is exploited to achieve more coherent segmentation. A Hough transform technique is used to find an initial approximation of the object boundary at the first frame of the sequence. Then, an active-contour model is used in a coarse-to-fine framework, for the estimation of a noisy LV boundary. The PCA transform is applied to form a reduced ordered orthonormal basis of the LV deformations based on a sequence of noisy boundary observations. Then this basis is used to constrain the motion of the active contour in subsequent frames, and thus provide more coherent identification. Results of epicardial boundary identification in B-mode images are presented.

Adult↗

PubMed1998

An adaptive backpropagation neural network for real-time ischemia episodes detection: development and performance analysis using the European ST-T database.

A supervised neural network (NN)-based algorithm was used for automated detection of ischemic episodes resulting from ST segment elevation or depression. The performance of the method was measured using the European ST-T database. In particular, the performance was measured in terms of beat-by-beat ischemia detection and in terms of the detection of ischemic episodes. The algorithm used to train the NN was an adaptive backpropagation (BP) algorithm. This algorithm drastically reduces training time (tenfold decrease in our case) when compared to the classical BP algorithm. The recall phase of the NN is then extremely fast, a fact that makes it appropriate for real-time detection of ischemic episodes. The resulting NN is capable of detecting ischemia independent of the lead used. It was found that the average ischemia episode detection sensitivity is 88.62% while the ischemia duration sensitivity is 72.22%. The results show that NN can be used in electrocardiogram (ECG) processing in cases where fast and reliable detection of ischemic episodes is desired as in the case of critical care units (CCU's).

Algorithms↗

PubMed1998

Teleworks: a CSCW application for remote medical diagnosis support and teleconsultation.

The present paper describes methods for the design of both synchronous and asynchronous computer-supported cooperative work (CSCW) procedures suitable for the medical application area and specifically for the purpose of medical teleconsultation and remote diagnosis support. The experimental implementation of a CSCW system built upon a PC/Windows platform is detailed as an example of a low-cost system suitable for adoption in a wide range of medical teleconsultation applications.

Computer Communication Networks↗

PubMed1997

Integration of digital angiography and gamma-camera diagnostic modalities to a generalized hospital information system.

Within the framework of the NIKA project for the development of a "Generalized System for Processing and Management of Medical Images", we have integrated a Digital Subtraction Angiography (DSA) station and a gamma-camera diagnostic modality to the newly developed generalized hospital-wide information system. The integration consists of acquiring, digitizing, converting and filing the information from the above diagnostic modalities to the hospital's Picture Archiving and Communication System (PACS). The PACS, which is installed in the Onasio Cardiosurgery Centre of Athens, Greece, is responsible for archival, cataloging, retrieval and viewing of the large volume of patient examination data accumulated during his/her stay in the Centre. The ultimate goal is for all patient data, from all different examinations, to be viewed on dedicated client workstations. Information from different modalities can then be simultaneously presented to the attending physician, for a complete picture of the patient history and condition.

Angiography, Digital Subtraction↗

PubMed1992

On AR modelling for MEG spectral estimation, data compression and classification.

The use of the autoregressive (AR) model for magnetoencephalogram (MEG) processing is examined and compared to other methods. Spectral estimation, classification and data compression of MEG signals are studied. In application to spectral estimation the AR model is compared to the classical modified periodogram method. Also, AR modelling appears to perform very successfully when used for the classification of normal and epileptic MEG signals. Finally, the 17:1 to 23:1 data compression achieved by AR modelling, along with the above-mentioned advantages, render it suitable for storage applications. For comparison, the method of feature selection via orthogonal expansion is used as a tool to achieve data reduction. It is seen that while effective, this is less drastic than the compression of data volume achieved by AR modelling.

Brain Mapping↗

PubMedDate not supplied

A review of compression methods for medical images in PACS.

As an introduction to Section C2 (medical imaging) of track C (Images and PACS) of MIE '97, an appropriate and timely topic concerns the coding for the transmission of medical images in PACS. Speed limitations of existing networks along with the explosive growth of image modalities with extremely high volume outputs have combined to make the issue of medical image coding one of the key considerations in the design of future PACS systems. Both lossless and lossy compression schemes are reviewed and compared, and the compression demands are presented of the main digital medical image modalities.

Angiography, Digital Subtraction↗

PubMedDate not supplied

Practical evaluation of standard-based low-cost video conferencing in telemedicine and epidemiological applications.

The results of the evaluation of use of low-cost video conferencing systems (VCSs) in telemedicine is presented. Applications sharing, a new feature of these systems, recently has allowed high-quality computer-supported collaborative work (CSCW). The video conferencing (VCing) equipment used was Intel ProShare 200 v2.0a. It is representative of other low-cost VCSs. The areas of application are epidemiology and telemedicine (orthopaedics and radiology). Potential end users filled out 58 evaluation questionnaires concerning user profiles, contents and benefits of the sessions, organizational aspects, user friendliness, user acceptance, cost effectiveness, technical and multipoint related aspects. Although the end users had a lot of computer experience, their knowledge in VCSs was rather limited. The users assessed the system capable of being integrated into routine work, despite a high organizational impact. The VCS is user friendly, application sharing being used in almost every session. Audio quality was not always sufficient. The remote video was sufficient, as was the quality of medical images such as CT, MRI or X-ray. The user acceptance of the system was high. Multipoint sessions require a structured protocol to be effective. Some technical problems with MCUs (Multipoint Control Units) occurred. The use of low-cost standard VCSs in telemedicine is advisable and is a good substitute for real meetings.

Cost-Benefit Analysis↗

PubMedDate not supplied

Design of CSCW applications for medical teleconsultation and remote diagnosis support.

Recent advances in telecommunication technology have permitted the implementation of tools for Computer Supported Cooperative Work (CSCW) based on real time transmission of different information types between two or more stations. The present paper describes methods for the design of both synchronous and asynchronous CSCW procedures suitable for the medical application area and specifically for the purpose of medical consultation and more generally, remote diagnosis support. The experimental implementation of such a CSCW system built upon a Personal Computer/Windows platform is detailed as an example of such a low-cost system suitable for adoption in a wide-range of medical teleconsultation applications.

Algorithms↗

PubMedDate not supplied

Network and data security design for telemedicine applications.

The maturing of telecommunication technologies has ushered in a whole new era of applications and services in the health care environment. Teleworking, teleconsultation, mutlimedia conferencing and medical data distribution are rapidly becoming commonplace in clinical practice. As a result, a set of problems arises, concerning data confidentiality and integrity. Public computer networks, such as the emerging ISDN technology, are vulnerable to eavesdropping. Therefore it is important for telemedicine applications to employ end-to-end encryption mechanisms securing the data channel from unauthorized access of modification. We propose a network access and encryption system that is both economical and easily implemented for integration in developing or existing applications, using well-known and thoroughly tested encryption algorithms. Public-key cryptography is used for session-key exchange, while symmetric algorithms are used for bulk encryption. Mechanisms for session-key generation and exchange are also provided.

Algorithms↗

PubMedDate not supplied

Hippocrates: an integrated platform for telemedicine applications.

This paper describes 'Hippocrates', an integrated platform for telemedicine applications. Hippocrates allows computer supported co-operative work based on patient data folders consisting of selected diagnostic images, annotation text, patient history and other information. All data transferred is encrypted to ensure confidentiality and integrity. It operates on a local level over TCP/IP LAN environment and on a remote level over public ISDN lines.

Computer Security↗