Reza Razaghi - Academia.edu (original) (raw)

Papers by Reza Razaghi

Bioengineering

Background: Aqueous humor outflow resistance in the trabecular meshwork (TM), juxtacanalicular co... more Background: Aqueous humor outflow resistance in the trabecular meshwork (TM), juxtacanalicular connective tissue (JCT), and Schlemm’s canal (SC) endothelium of the conventional outflow pathway actively contribute to intraocular pressure (IOP) regulation. Outflow resistance is actively affected by the dynamic outflow pressure gradient across the TM, JCT, and SC inner wall tissues. The resistance effect implies the presence of a fluid–structure interaction (FSI) coupling between the outflow tissues and the aqueous humor. However, the biomechanical interactions between viscoelastic outflow tissues and aqueous humor dynamics are largely unknown. Methods: A 3D microstructural finite element (FE) model of a healthy human eye TM/JCT/SC complex was constructed with elastic and viscoelastic material properties for the bulk extracellular matrix and embedded elastic cable elements. The FE models were subjected to both idealized and a physiologic IOP load boundary using the FSI method. Results:...

Injury, 2022

BACKGROUND Eye injuries comprise 10-13% of civilian improvised explosive device (IED) injuries. T... more BACKGROUND Eye injuries comprise 10-13% of civilian improvised explosive device (IED) injuries. The bomb blast wave induces a normal and shear forces on the tissues, causing a large acute IOP elevation. This study calculated the biomechanical stresses and strains in the eye due to IED explosion via eye-specific fluid-structure interaction (FSI) models. METHODS Blast occurred at 2, 3, and 4 m from the front and side of the victim and the weights of the IED were 1 and 2 kg. The ground was covered with the deformable soil to mimic the realistic IED explosion condition and reflect the blast wave. RESULTS The IOP elevation of ∼6,000-48,000 mmHg was observed in the eyes while the highest IOP was occurred with the IED weight and distance of 2 kg and 2 m (front) and the lowest was occurred with the IED weight and distance of 1 kg and 4 m (side). Our findings suggest the importance of the victim location and orientation concerning the blast wave when it comes to ocular injury assessment. IOP elevation of ∼2900 and ∼2700 mmHg were observed in ∼1.6 ms after the blast for the IEDS weight of 2 kg and a victim distance of 2 m in front and side blasts, respectively, in consistence with the literature. Nonetheless, IOPs were considerably higher after ∼1.6 ms due to the merging of the bomb blast wave and its reflection off the ground. CONCLUSIONS The stresses and strains were highest for the frontal blast. Both side and frontal blasts caused higher stresses and strains at the rectus muscle insertions where the sclera is thinnest and prone to rupture. Blast angle has no considerable role in the resultant IOP. Front blast with a heavier IED resulted a higher stresses and deformations in the eye connective tissues compared to the side blast.

Computer Methods and Programs in Biomedicine

There have been different stress-strain definitions to measure the elastic modulus of spongy mate... more There have been different stress-strain definitions to measure the elastic modulus of spongy materials, especially polyvinyl alcohol (PVA) sponge. However, there is no agreement as to which stress-strain definition should be implemented. This study was aimed to show how different results are given by the various definitions of stress-strain used, and to recommend a specific definition when testing spongy materials. A fabricated PVA sponge was subjected to a series of tensile tests in order to measure its mechanical properties. Three stress definitions (second Piola-Kichhoff stress, engineering stress, and true stress) and four strain definitions (Almansi-Hamel strain, Green-St. Venant strain, engineering strain, and true strain) were used to determine the elastic modulus. The results revealed that the Almansi-Hamel strain definition exhibited the highest non-linear stress-strain relation and, as a result, may overestimate the elastic modulus at different stress definitions (second P...

Background So far, in the stress calculation of the plaques, the blood has been simulated as a si... more Background So far, in the stress calculation of the plaques, the blood has been simulated as a single component, and the role of the mechanical interaction between the red blood cells (RBCs), white blood cells (WBCs), and plasma with that of the plaque has been neglected. This study was aimed at proposing an interactive method based on smoothed particle hydrodynamics (SPH), a fully mesh-free particle approach, to simulate the blood as a fluid with free surfaces, including the RBC, WBC, and plasma, to determine the vulnerable plaque on a basis of the induced stresses. Materials and methods A three-dimensional (3D) finite element (FE) model of the atherosclerotic coronary artery was established according to the CT/MRI data of a patient. SPH method was employed toward our blood particles simulation by deriving the force density fields directly from the Navier-Stokes equation and incorporated into the FE equations. The stress in the plaque, necrotic core (NC), and arterial layers were t...

Computer Methods and Programs in Biomedicine

Journal of the Mechanical Behavior of Biomedical Materials

Journal of the Mechanical Behavior of Biomedical Materials

Engineering Failure Analysis

Trauma

Background There is a lack of knowledge on the magnitudes of the biomechanical stresses and defor... more Background There is a lack of knowledge on the magnitudes of the biomechanical stresses and deformations occurring in the cerebral arterial wall after traumatic brain injury (TBI). Experimental techniques are unable to calculate the stresses and deformations in the cerebral arterial wall after TBI; therefore, the application of numerical simulations, such as finite element modeling, is preferred. Methods This study was aimed to calculate the stresses and deformations as well as the alteration in the pressure and velocity of the blood in the cerebrovascular artery using a fluid–structure interaction model. Results The results revealed considerable increase in the pressure and velocity of the blood which might lead to cerebrovascular damage followed by hemorrhage. The arterial wall showed the highest deformation of 0.047 mm in the X direction which was higher than that in the Y (0.035–0.050 mm) and Z (0.019–0.030 mm) directions. Conclusions These results have implications not only for...

Proceedings of the Institution of Mechanical Engineers, Part P: Journal of Sports Engineering and Technology

Sport is responsible for between 25% and 40% of all eye injuries. Trauma is integrated to the nat... more Sport is responsible for between 25% and 40% of all eye injuries. Trauma is integrated to the nature of the sport, especially boxing, which is considered a high-risk sport for ocular injuries. Boxing not only brings about injury to the external side of the eye, but in nearly one third of cases, the intraocular components of the eye are also damaged, followed by serious visual acuity complications. However, so far there is a paucity of knowledge on the ocular injury as a result of a strong hook to the face during boxing. This study was, therefore, aimed to perform a dynamic finite element simulation to calculate the stresses and deformations to the components of the eye (i.e. the cornea, aqueous body, iris, ciliary body, vitreous body, sclera, retina, and optic nerve) as a consequence of a hook to the zygomatic and frontal skull bones of a boxer. To do that, well-verified finite element models of the human skull, eye, and punch developed by the current authors were employed to simula...

Computer Methods and Programs in Biomedicine

Theoretical and Applied Mechanics Letters

Journal of Medical Engineering & Technology

Computer Methods and Programs in Biomedicine

International Journal of Industrial Ergonomics

Journal of the Brazilian Society of Mechanical Sciences and Engineering

Current Pharmaceutical Design

Current Pharmaceutical Design

Bioengineering

Background: Aqueous humor outflow resistance in the trabecular meshwork (TM), juxtacanalicular co... more Background: Aqueous humor outflow resistance in the trabecular meshwork (TM), juxtacanalicular connective tissue (JCT), and Schlemm’s canal (SC) endothelium of the conventional outflow pathway actively contribute to intraocular pressure (IOP) regulation. Outflow resistance is actively affected by the dynamic outflow pressure gradient across the TM, JCT, and SC inner wall tissues. The resistance effect implies the presence of a fluid–structure interaction (FSI) coupling between the outflow tissues and the aqueous humor. However, the biomechanical interactions between viscoelastic outflow tissues and aqueous humor dynamics are largely unknown. Methods: A 3D microstructural finite element (FE) model of a healthy human eye TM/JCT/SC complex was constructed with elastic and viscoelastic material properties for the bulk extracellular matrix and embedded elastic cable elements. The FE models were subjected to both idealized and a physiologic IOP load boundary using the FSI method. Results:...

Injury, 2022

BACKGROUND Eye injuries comprise 10-13% of civilian improvised explosive device (IED) injuries. T... more BACKGROUND Eye injuries comprise 10-13% of civilian improvised explosive device (IED) injuries. The bomb blast wave induces a normal and shear forces on the tissues, causing a large acute IOP elevation. This study calculated the biomechanical stresses and strains in the eye due to IED explosion via eye-specific fluid-structure interaction (FSI) models. METHODS Blast occurred at 2, 3, and 4 m from the front and side of the victim and the weights of the IED were 1 and 2 kg. The ground was covered with the deformable soil to mimic the realistic IED explosion condition and reflect the blast wave. RESULTS The IOP elevation of ∼6,000-48,000 mmHg was observed in the eyes while the highest IOP was occurred with the IED weight and distance of 2 kg and 2 m (front) and the lowest was occurred with the IED weight and distance of 1 kg and 4 m (side). Our findings suggest the importance of the victim location and orientation concerning the blast wave when it comes to ocular injury assessment. IOP elevation of ∼2900 and ∼2700 mmHg were observed in ∼1.6 ms after the blast for the IEDS weight of 2 kg and a victim distance of 2 m in front and side blasts, respectively, in consistence with the literature. Nonetheless, IOPs were considerably higher after ∼1.6 ms due to the merging of the bomb blast wave and its reflection off the ground. CONCLUSIONS The stresses and strains were highest for the frontal blast. Both side and frontal blasts caused higher stresses and strains at the rectus muscle insertions where the sclera is thinnest and prone to rupture. Blast angle has no considerable role in the resultant IOP. Front blast with a heavier IED resulted a higher stresses and deformations in the eye connective tissues compared to the side blast.

Computer Methods and Programs in Biomedicine

There have been different stress-strain definitions to measure the elastic modulus of spongy mate... more There have been different stress-strain definitions to measure the elastic modulus of spongy materials, especially polyvinyl alcohol (PVA) sponge. However, there is no agreement as to which stress-strain definition should be implemented. This study was aimed to show how different results are given by the various definitions of stress-strain used, and to recommend a specific definition when testing spongy materials. A fabricated PVA sponge was subjected to a series of tensile tests in order to measure its mechanical properties. Three stress definitions (second Piola-Kichhoff stress, engineering stress, and true stress) and four strain definitions (Almansi-Hamel strain, Green-St. Venant strain, engineering strain, and true strain) were used to determine the elastic modulus. The results revealed that the Almansi-Hamel strain definition exhibited the highest non-linear stress-strain relation and, as a result, may overestimate the elastic modulus at different stress definitions (second P...

Background So far, in the stress calculation of the plaques, the blood has been simulated as a si... more Background So far, in the stress calculation of the plaques, the blood has been simulated as a single component, and the role of the mechanical interaction between the red blood cells (RBCs), white blood cells (WBCs), and plasma with that of the plaque has been neglected. This study was aimed at proposing an interactive method based on smoothed particle hydrodynamics (SPH), a fully mesh-free particle approach, to simulate the blood as a fluid with free surfaces, including the RBC, WBC, and plasma, to determine the vulnerable plaque on a basis of the induced stresses. Materials and methods A three-dimensional (3D) finite element (FE) model of the atherosclerotic coronary artery was established according to the CT/MRI data of a patient. SPH method was employed toward our blood particles simulation by deriving the force density fields directly from the Navier-Stokes equation and incorporated into the FE equations. The stress in the plaque, necrotic core (NC), and arterial layers were t...

Computer Methods and Programs in Biomedicine

Journal of the Mechanical Behavior of Biomedical Materials

Journal of the Mechanical Behavior of Biomedical Materials

Engineering Failure Analysis

Trauma

Background There is a lack of knowledge on the magnitudes of the biomechanical stresses and defor... more Background There is a lack of knowledge on the magnitudes of the biomechanical stresses and deformations occurring in the cerebral arterial wall after traumatic brain injury (TBI). Experimental techniques are unable to calculate the stresses and deformations in the cerebral arterial wall after TBI; therefore, the application of numerical simulations, such as finite element modeling, is preferred. Methods This study was aimed to calculate the stresses and deformations as well as the alteration in the pressure and velocity of the blood in the cerebrovascular artery using a fluid–structure interaction model. Results The results revealed considerable increase in the pressure and velocity of the blood which might lead to cerebrovascular damage followed by hemorrhage. The arterial wall showed the highest deformation of 0.047 mm in the X direction which was higher than that in the Y (0.035–0.050 mm) and Z (0.019–0.030 mm) directions. Conclusions These results have implications not only for...

Proceedings of the Institution of Mechanical Engineers, Part P: Journal of Sports Engineering and Technology

Sport is responsible for between 25% and 40% of all eye injuries. Trauma is integrated to the nat... more Sport is responsible for between 25% and 40% of all eye injuries. Trauma is integrated to the nature of the sport, especially boxing, which is considered a high-risk sport for ocular injuries. Boxing not only brings about injury to the external side of the eye, but in nearly one third of cases, the intraocular components of the eye are also damaged, followed by serious visual acuity complications. However, so far there is a paucity of knowledge on the ocular injury as a result of a strong hook to the face during boxing. This study was, therefore, aimed to perform a dynamic finite element simulation to calculate the stresses and deformations to the components of the eye (i.e. the cornea, aqueous body, iris, ciliary body, vitreous body, sclera, retina, and optic nerve) as a consequence of a hook to the zygomatic and frontal skull bones of a boxer. To do that, well-verified finite element models of the human skull, eye, and punch developed by the current authors were employed to simula...

Computer Methods and Programs in Biomedicine

Theoretical and Applied Mechanics Letters

Journal of Medical Engineering & Technology

Computer Methods and Programs in Biomedicine

International Journal of Industrial Ergonomics

Journal of the Brazilian Society of Mechanical Sciences and Engineering

Current Pharmaceutical Design

Current Pharmaceutical Design