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N D Panagiotacopulos

Publications and source records attributed to N D Panagiotacopulos.

5 recordsLinked to original sources
PubMed1987

A mechanical model for the human intervertebral disc.

Stress relaxation experiments were performed on specimens from a human intervertebral disc. Specimens were made from the nucleus pulposus and from the external lamellae of the anulus fibrosus in two different orientations. Tests were run with varying moisture content so as to develop a relaxation master curve. A model was developed based on the experimental data. It was found that the short term master curve for the lamellae of the anulus and nucleus are similar, whereas the long term rubbery plateau is different between the lamellae and the nucleus. It was also established that the master curves for different lamellae and the nucleus were shifted relative to each other in the time domain due to changes in water content. The average relaxation modulus of the whole disc was obtained by averaging the properties between the anulus and nucleus. This model was then used for studies of Schmorl's nodes, of degenerated discs and for circumstances in which hydration is considered to be important.

Body Water↗
PubMed1987

Water content in human intervertebral discs. Part I. Measurement by magnetic resonance imaging.

Tension-relaxation experiments were performed on human disc lamellae specimens. The water content was found to affect the viscoelastic behavior and a master relaxation curve was constructed from the experimental data. The water content of disc phantoms is measured by magnetic resonance imaging (MRI) techniques. MRI was used to compare the discs of patients of different ages. The possibility of obtaining cross-sectional water distribution in human intervertebral disc material using MRI techniques and its relation to the disc's mechanical properties was explored, with the goal of constructing a realistic mathematical model of the disc which takes into account the water content of the disc.

Body Water↗
PubMed1987

Water content in human intervertebral discs. Part II. Viscoelastic behavior.

Water content of intervertebral discs is a significant aspect of both viscoelastic behavior and age-related degenerative changes. Using water content as a dependent variable, stress-relaxation was measured using standardized anulus fibrosus specimens strained at various levels of strain. Synthesis of experimental data into a master relaxation curve allows prediction of specimen response over time intervals not readily accessible experimentally. A quantitative understanding of the role of water content may have important clinical application, since magnetic resonance imaging is a tool which should allow water content determination in vivo.

Biomechanical Phenomena↗
PubMedDate not supplied

Digital image processing, a potential noninvasive technique in the diagnosis of diseased intervertebral discs.

The detection of the posterior edge of the L4-L5 intervertebral disc has been accomplished by applying digital image processing techniques on conventional lateral radiograms of the spine, and the method is described. The results of this study have shown that there can be substantial absorption at the site of the disc if the radiogram is properly taken; the existing information on the radiogram can be processed so that an improvement in the diagnostic quality of the radiogram can be achieved; and the edge of the posterior portion of the disc can be determined. This study, although a preliminary one, opens new possibilities for a safer and probably more accurate way of diagnosing herniated discs.

Analog-Digital Conversion↗