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BioMed Research International
Volume 2013 (2013), Article ID 197479, 5 pages
http://dx.doi.org/10.1155/2013/197479
Research Article

Determination of Poisson Ratio of Bovine Extraocular Muscle by Computed X-Ray Tomography

1Department of Mechanical and Automotive Engineering, Gachon University, Seongnam-Si, Gyeonggi-do 461-701, Republic of Korea
2Department of Ophthalmology, Jules Stein Eye Institute, University of California, Los Angeles, CA 90095-7002, USA
3Department of Mechanical Engineering, University of California, Los Angeles, CA, USA
4Biomedical Engineering Interdepartmental Program, University of California, Los Angeles, CA, USA
5Neuroscience Interdepartmental Program, University of California, Los Angeles, CA, USA
6Department of Neurology, University of California, Los Angeles, CA, USA

Received 12 October 2012; Accepted 4 December 2012

Academic Editor: José M. Vilar

Copyright © 2013 Hansang Kim et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

The Poisson ratio (PR) is a fundamental mechanical parameter that approximates the ratio of relative change in cross sectional area to tensile elongation. However, the PR of extraocular muscle (EOM) is almost never measured because of experimental constraints. The problem was overcome by determining changes in EOM dimensions using computed X-ray tomography (CT) at microscopic resolution during tensile elongation to determine transverse strain indicated by the change in cross-section. Fresh bovine EOM specimens were prepared. Specimens were clamped in a tensile fixture within a CT scanner (SkyScan, Belgium) with temperature and humidity control and stretched up to 35% of initial length. Sets of 500–800 contiguous CT images were obtained at 10-micron resolution before and after tensile loading. Digital 3D models were then built and discretized into 6–8-micron-thick elements. Changes in longitudinal thickness of each microscopic element were determined to calculate strain. Green’s theorem was used to calculate areal strain in transverse directions orthogonal to the stretching direction. The mean PR from discretized 3D models for every microscopic element in 14 EOM specimens averaged (SD). The measured PR of bovine EOM is thus near the limit of incompressibility.