Biomedical subjects

D Lymberopoulos

Publications and source records attributed to D Lymberopoulos.

7 recordsLinked to original sources

PubMed2003

Compression assessment based on medical image quality concepts using computer-generated test images.

Compression algorithms are widely used in medical imaging systems for efficient image storage, transmission, and display. In the acceptance of lossy compression algorithms in the clinical environment, important factors are the assessment of 'visually lossless' compression thresholds, as well as the development of assessment methods requiring fewer data and time than observer performance based studies. In this study a set of quantitative measurements related to medical image quality parameters is proposed for compression assessment. Measurements were carried out using region of interest (ROI) operations on computer-generated test images, with characteristics similar to radiographic images. As a paradigm, the assessment of the lossy Joint Photographic Expert Group (JPEG) algorithm, available in a telematics application for healthcare, is presented. A compression ratio of 15 was found as the visually lossless threshold for the JPEG lossy algorithm, in agreement with previous observer performance studies. Up to this ratio low contrast discrimination is not affected, image noise level is decreased, high contrast line-pair amplitude is decreased by less than 3%, and input/output gray level differences are minor (less than 1%). This type of assessment provides information regarding the type of loss, offering cost and time benefits, in parallel with the advantages of test image adaptation to the requirements of a certain imaging modality and clinical study.

Algorithms↗

PubMed2001

A new concept toward computer-aided medical diagnosis--a prototype implementation addressing pulmonary diseases.

The original concept that led to the structuring of a computer-based medical decision support system (DSS) that is able to support a physician's diagnosis is introduced in this paper. The concept's implementation modeled a generic DSS, the core of which are an integrated knowledge/information base (KIB) along with the inference properties of a data evaluator. The KIB encapsulates the necessary medical knowledge and experience in the form of rules and constraints, preemptive tasks, and actual patients' clinical data. The data evaluator handles approved medical subjective and objective criteria for assessing the KIB's data. The data evaluator incorporates a medical standard data gathering and decision process, structured upon the principles of the clinical differential diagnosis methodology and has been integrated in the system by means of both algorithmic and artificial intelligence techniques. The novel model and the resulted computer-based package have been extensively tested under the Pulmonary Department, University Regional Hospital Patras, Patras, Greece.

Artificial Intelligence↗

PubMed1999

A new perspective in learning pattern generation for teaching neural networks.

This article deals with the Learning Patterns (LPs)' generation, a major aspect of Feed-Forward Artificial Neural Networks (FANNs)' learning process. Currently, more work is done to understand the mechanisms and improve the speed, learning accuracy, and implementation features of FANNs' teaching algorithms, though little is done towards the development of enhanced techniques that would extract experts' knowledge (from examples, rules, etc.) and obtain standardised LPs that would improve this learning process. A new approach in generating LPs is thereby introduced, that is used to train a new Medical Decision Support System (MDSS) based on FANNs, and its performance is analysed and compared with previous methods. It can handle incomplete data archives, individually boost any particular dataum special characteristics, and its application induces the FANNs to show better convergent facets. The efficiency of the resulting MDSS was thoroughly tested by pulmonologists and haematologists using medical data archives of a regional hospital.

Journal Article↗

PubMed1999

Telemedicine technology and applications for home hemodialysis.

Home hemodialysis (HD) for the treatment of patients with end-stage renal disease (ESRD) was first put into practice about 30 years ago. In this paper we describe the application of telematics monitoring services (TMS) for supporting patients who need home or satellite HD (SHD). For the clinical trials two modified HD machines were located in the renal unit and a central control station (UNIX workstation with multimedia PC-terminal) was located in another room of the hospital. Bi-directional communication between modified HD machines and central control station was managed via ISDN (Integrated Services Digital Network) links. Using these HD-machines 150 HD sessions were performed in nine patients over a period of five months. This system enabled on-line remote supervision of the HD machine-related functions (air in the blood, leak of blood, low conductivity etc.) and the clinical condition of patients through measurement of blood pressure (BP), pulse rate, PO2 (pulse oxymetry) and electrocardiogram (ECG) from the central control station (CCS). The user checked the type of alarm/warning, its appearance on HD machines and multimedia terminal units (MTU), the action of the protective system and the appearance of consultative messages from CCS on the remote terminal unit RTU. According to the data collected, the disturbances of HD machine function were visible and audible in the CCS and the user messages were always observed on the RTU. No unusual dialysis-associated complications were observed, all data and alarms/warnings were transmitted correctly and patients had adequate HD treatment.

Female↗

PubMed1995

Orthopnea due to an aneurysm of the thoracic aorta.

Aneurysms of the thoracoic aorta may on rare occasions lead to shortness of breath by external compression of the tracheobronchial tree. We report the case of a patient who presented with orthopnea due to extensive compression of the trachea and the major airways by a large aneurysm of the ascending aorta.

Airway Obstruction↗

PubMed1993

Salivary immunoglobulin A production in chronic bronchitis patients given an orally administered bacterial extract.

The concentration of secretory immunoglobulin A (IgA) has been measured by the immunodiffusion method in 28 chronic bronchitis patients (group A) and in 11 comparable patients receiving corticosteroid therapy (0.5 mg/kg/day prednisone; group B). The measurements have been taken before and after oral administration of Broncho-Vaxom which is an extract of bacteria that usually cause infection of the respiratory tract. The mean concentration of secretory IgA in the saliva was increased by over 130% after the 10-day administration of the preparation to group A patients. This increase was statistically significant between the 12th and 40th day after the beginning of the treatment (p < 0.001). It fell to initial levels after 1 month in 15 patients (group A2) who received a single treatment course. In 13 patients (group A1) who received a second treatment course, beginning 1 month after termination of the first course, the high concentration of IgA in saliva persisted for at least 3 months. The saliva IgA was increased by over 35% in 11 chronic bronchitis patients (group B) who received corticosteroid therapy. In this group of patients the rise of IgA levels began later than in group A. The IgA fell to initial level after 1 month in 5 patients (group B2) who received a single treatment course. In 6 patients (group B1) who received a second treatment course the high concentration persisted longer. The saliva level of IgA in groups A and A1 was higher than in groups B and B1 (p < 0.05 and p < 0.001, respectively). No differences of IgA in the saliva between groups A2 and B2 were found during the study.

Adjuvants, Immunologic↗

PubMedDate not supplied

A tool for designing digital test objects for module performance evaluation in medical digital imaging.

Currently, medical digital imaging systems are characterized by the introduction of additional modules such as digital display, image compression and image processing, as well as film printing and digitization. These additional modules require performance evaluation to ensure high image quality. A tool for designing computer-generated test objects applicable to performance evaluation of these modules is presented. The test objects can be directly used as digital images in the case of film printing, display, compression and image processing, or indirectly as images on film in the case of digitization. The performance evaluation approach is quality control protocol based. Digital test object design is user-driven according to specifications related to the requirements of the modules being tested. The available quality control parameters include input/output response curve, high contrast resolution, low contrast discrimination, noise, geometric distortion and field uniformity. The tool has been designed and implemented according to an object oriented approach in Visual C++ 5.0, and its user interface is based on the Microsoft Foundation Class Library version 4.2, which provides interface items such as windows, dialog boxes, lists, buttons, etc. The compatibility with DICOM 3.0 part 10 image formats specifications allows the integration of the tool in the existing software framework for medical digital imaging systems. The capability of the tool is demonstrated by direct use of the test objects in case of image processing, and indirect use of the test objects in case of film digitization.

Algorithms↗