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Biomedical subjects

I Pitas

Publications and source records attributed to I Pitas.

7 recordsLinked to original sources
PubMed1997

3D reconstruction of two C-shape mandibular molars.

Two mandibular second molars, with an indication of C-shape morphology were processed for 3-D reconstruction. After serial cross sectioning, photographs of the sections were digitized and by using surface representation, 3D reconstruction was achieved. The first molar as the 3D reconstruction showed was single rooted with one C-shaped root canal with two foramens, while the second one was double rooted with two root canals, one C-shaped and one thin, having a common foramen.

Anatomy, Cross-Sectional↗
PubMed1997

Computerized 3-D reconstruction of two "double teeth".

"Double teeth" is a root malformation in the dentition and the purpose of this study was to reconstruct three-dimensionally the external and internal morphology of two "double teeth". The first set of "double teeth" was formed by the conjunction of a mandibular molar and a premolar, and the second by a conjunction of a maxillary molar and a supernumerary tooth. The process of 3-D reconstruction included serial cross-sectioning, photographs of the sections, digitization of the photographs, extraction of the boundaries of interest for each section, surface representation using triangulation and, finally, surface rendering using photorealistic effects. The resulting three-dimensional representations of the two teeth helped us visualize their external and internal anatomy. The results showed: a) in the first case, fusion of the radical and coronal dentin, as well as fusion of the pulp chambers; and b) in the second case, fusion only of the radical dentin and the pulp chambers.

Anatomy, Cross-Sectional↗
PubMed1996

Non-linear algorithms for processing biological signals.

This paper illustrates different approaches to the analysis of biological signals based on non-linear methods. The performance of such approaches, despite the greater methodological and computational complexity is, in many instances, more successful compared to linear approaches, in enhancing important parameters for both physiological studies and clinical protocols. The methods introduced employ median filters for pattern recognition, adaptive segmentation, data compression, prediction and data modelling as well as multivariate estimators in data clustering through median learning vector quantizers. Another approach described uses Wiener-Volterra kernel technique to obtain a satisfactory estimation and causality test among EEG recordings. Finally, methods for the assessment of non-linear dynamic behaviour are discussed and applied to the analysis of heart rate variability signal. In this way invariant parameters are studied which describe non-linear phenomena in the modelling of the physiological systems under investigation.

Algorithms↗
PubMed1995

Three computer methods to reconstruct pulpal blood vessels and nerves.

This study describes three methods of computerized three-dimensional reconstruction of the main neurovascular pulpal bundle of human teeth, using serial cross-paraffin sections, digital image processing, and three-dimensional computer graphics. These methods are surface representation, representation by means of a stack of slices, and volume representation.

Adolescent↗
PubMed1995

Computerized reconstruction of TEM examined pulpal blood vessels and nerves.

Five healthy premolars were used for transmission electron microscopy examination and three-dimensional (3D) reconstruction of pulpal blood vessels and their surrounding nerves. Serial Epon thin sections were taken from specimens. After a series of preprocessing steps that included digitization, contrast enhancement, slice alignment, segmentation and interpolation, three dimensional surface representation was performed using the triangulation method. The findings showed that vessels were usually accompanied by a number of myelinated and unmyelinated nerves. The nerves shared a more or less common course with the vessels. Small arteries presented greater number of nerves in their vicinity, compared to small veins. In the sections examined, no direct contact between the nerve trunks and the wall of the vessels was found; the closest distance measured was approximately 67 microns. The common course of vessels and nerves suggested autonomic innervation on part of the myelinated axons.

Adult↗
PubMed1992

Optimum nonlinear signal detection and estimation in the presence of ultrasonic speckle.

A unified approach to the design of nonlinear filters for speckle suppression in ultrasound B-mode images is presented. The detection of the (lesion) signal is formulated as a binary hypothesis-testing problem. The structure of the optimal decision rules is derived both in the case where the lesion signal is assumed either a constant or random variable. In the case of a constant signal, the maximum likelihood (ML) estimator and the optimal L-estimator are derived. In the case of a random lesion signal, the maximum a posteriori probability estimator of the lesion signal has also been found. Experimental results verify the superiority of the proposed ML-estimator and the L-estimator over the straightforward choice of an arithmetic mean for speckle filtering in simulated tissue mimicking phantom ultrasound B-mode images.

Equipment Design↗