Biomechanics / Biomechanical Engineering
Mahdieh Mosayebi; Afsaneh Mojra
Volume 13, Issue 1 , April 2019, , Pages 31-44
Abstract
Intervertebral disc (IVD) provides flexibility and shock absorption for the spine in the load transmission procedure. Disc degeneration may occur as a result of aging and inappropriate types of loading. Assessing biomechanical parameters of intact IVD in comparison to the degenerated disc with different ...
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Intervertebral disc (IVD) provides flexibility and shock absorption for the spine in the load transmission procedure. Disc degeneration may occur as a result of aging and inappropriate types of loading. Assessing biomechanical parameters of intact IVD in comparison to the degenerated disc with different grades of degeneration can facilitate the detection procedure and planning for suitable therapeutic treatment. In the present study, a real three-dimensional model of cercival IVD ( - with adjacent vertebrae is constructed by using computed tomography (CT-scan) images. In order to accurately define mechanical properties, the disc and the vertebrae are modelled as poroviscoelastic and poroelastic materials, respectively. A porous medium approach is adopted to consider the considerable water content of both media alongside the solid matrix. For the solid phase of the IVD, the related viscoelastic parameters are extracted from an experimental test on a sheep lumbar intervertebral disc and stress vs. time data are fitted to the generalized Maxwell model with two Maxwell arms. By employing the finite element method, time-dependent response of the intact IVD and three different levels of the degenerated IVD (mild, moderate and severe) are studied in a relaxation test. Results indicate that during relaxation procedure, intradiscal fluid velocity decreases as a result of disc degeneration. This may oppositely affect the flexibility of IVD in the load bearing. It is also observed that stress relaxation of the severe degenerated IVD almost increases up to 16% relative to the intact IVD. Assessing the amount of disc bulging under load application shows enhancement for the degenerated disc compared to the intact disc.
Bioheat Transfer
Farshad Bahramian; Afsaneh Mojra
Volume 10, Issue 3 , October 2016, , Pages 245-256
Abstract
The aim of this study is to investigate the use of thermography technique for detection of thyroid gland embedded in the neck through a numerical and an experimental approach. To this end, a real 3D model of the human neck and its primary organs including trachea, thyroid gland, common carotid artery ...
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The aim of this study is to investigate the use of thermography technique for detection of thyroid gland embedded in the neck through a numerical and an experimental approach. To this end, a real 3D model of the human neck and its primary organs including trachea, thyroid gland, common carotid artery and internal jugular vein is constructed based on the computerized tomography (CT) scan images of a healthy case and a case of thyroid cancer. The model is used for analyzing bio-heat transfer in the neck. In the thermal analysis the thyroid gland is considered as a heat source via specific function that generates heat based on the thyroid temporal temperature. Moreover, external convection through the neck skin surface and the ambient air, an internal convection through the inner layer of trachea and breathed air and heat transfer through the artery and the vein are considered. The result is the temperature distribution (thermogram) on the skin surface of the neck which reveals an approximate 0.5 -1.4 ˚C temperature increase on the area above thyroid gland for the healthy case. Studying effects of the thyroid cancer on the thermogram shows an approximate 0.7 -1.6 ˚C temperature increase due to the increased metabolic rate of the cancerous tumor compared to the healthy tissue. In order to practically investigate the applicability of thermography technique, a healthy case is examined by a high precision thermographic camera in similar conditions to the numerical simulation. Similar temperature increase due to the existence of the thyroid gland by the simulation and experiment affirmed the capability of the thermography method in the thyroid gland detection on the skin surface of the neck.
