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Biomedical subjects

G K Matsopoulos

Publications and source records attributed to G K Matsopoulos.

8 recordsLinked to original sources
PubMed2001

Impaired P600 in neuroleptic naive patients with first-episode schizophrenia.

Deficits of working memory (WM) are recognized as an important pathological feature in schizophrenia. Since the P600 component of event related potentials has been hypothesized that represents aspects of second-pass parsing processes of information processing, and is related to WM, the present study focuses on P600 elicited during a WM test in drug-naive first-episode schizophrenics (FES) compared to healthy controls. We examined 16 drug-naive first-episode schizophrenic patients and 23 healthy controls matched for age and sex. Compared with controls schizophrenic patients showed reduced P600 amplitude on left temporoparietal region and increased P600 amplitude on left occipital region. With regard to the latency, the patients exhibited significantly prolongation on right temporoparietal region. The obtained pattern of differences classified correctly 89.20% of patients. Memory performance of patients was also significantly impaired relative to controls. Our results suggest that second-pass parsing process of information processing, as indexed by P600, elicited during a WM test, is impaired in FES. Moreover, these findings lend support to the view that the auditory WM in schizophrenia involves or affects a circuitry including temporoparietal and occipital brain areas.

Acoustic Stimulation↗
PubMed2001

Abnormal P600 in heroin addicts with prolonged abstinence elicited during a working memory test.

The P600 component of event-related potentials, believed to be generated by anterior cingulate gyrus and basal ganglia, is considered as an index of aspects of second-pass parsing processes of information processing, having much in common with working memory (WM) systems. Moreover, dysfunction of these brain structures as well as WM deficits have been implicated in the pathophysiology of opioid addicts. The present study is focused on P600 elicited during a WM test in twenty heroin addicts with prolonged abstinence compared with an equal number of healthy controls. The results showed significantly prolonged latencies at right hemisphere, specifically at Fp2 abduction. Moreover, memory performance of patients did not differ from that of normal controls. These findings may indicate that abstinent heroin addicts manifest abnormal aspects of second-pass parsing processes as are reflected by the P600 latencies, elicited during a WM test. Additionally, the P600 might serve as a valuable investigative tool for a more comprehensive understanding of the neurobiological substrate of drug abuse.

Adult↗
PubMed2000

Reengineering the biomedical-equipment procurement process through an integrated management information system.

The design of each new hospital site is typically preceded by decisions on the most appropriate level of biomedical equipment which significantly influences the layout of the hospital departments which are under construction. The most appropriate biomedical equipment should ideally be decided upon considering a series of demographic and social parameters of the hospital and international regulations and standards. This information should ultimately be distilled to proper technical specifications. This paper proposes a streamlined management process related to the procurement of biomedical equipment for new hospital sites or for those under expansion. The new management process aims to increase the efficiency of the experts involved in the definition of the most appropriate level of equipment and its technical specifications. It also addresses all aspects of the biomedical equipment-selection cycle, including the evaluation of the bids submitted by the equipment suppliers. The proposed process is assisted by a management information system, which integrates all related data-handling operations. It provides extensive decision-support facilities to the expert and a platform for the support of knowledge re-use in the field of biomedical-equipment selection.

Competitive Bidding↗
PubMed1999

Automatic retinal image registration scheme using global optimization techniques.

Retinal image registration is commonly required in order to combine the complementary information in different retinal modalities. In this paper, a new automatic scheme to register retinal images is presented and is currently tested in a clinical environment. The scheme considers the suitability and efficiency of different image transformation models and function optimization techniques, following an initial preprocessing stage. Three different transformation models--affine, bilinear and projective--as well as three optimization techniques--downhill simplex method, simulated annealing and genetic algorithms--are investigated and compared in terms of accuracy and efficiency. The registration of 26 pairs of Fluoroscein Angiography and Indocyanine Green Chorioangiography images with the corresponding Red-Free retinal images, showed the superiority of combining genetic algorithms with the affine and bilinear transformation models. A comparative study of the proposed automatic registration scheme against the manual method, commonly used in the clinical practice, is finally presented showing the advantage of the proposed automatic scheme in terms of accuracy and consistency.

Algorithms↗
PubMedDate not supplied

A novel and efficient implementation of the marching cubes algorithm.

In this paper, a novel and efficient implementation of the marching cubes (MC) algorithm is presented for the reconstruction of anatomical structures from real three-dimensional medical data. The proposed approach is based on a generic rule, able to triangulate all 15 standard cube configurations used in the classical MC algorithm as well as additional cases presented in the literature. The proposed implementation of the MC algorithm can handle the Type A 'hole problem' which occurs when at least one cube face has an intersection point in each of its four edges. Theoretical and experimental results demonstrate the ability of the new implementation to reproduce standard MC results, resolving Type A 'hole problem'. Finally, the proposed implementation was applied to real medical date to reconstruct anatomical structures. The output of the proposed technique is in WWW compliant format.

Algorithms↗