How growing tumour impacts intracranial pressure and deformation mechanics of brain

Brain is an actuator for control and coordination. When a pathology arises in cranium, it may leave a degenerative, disfiguring and destabilizing impact on brain physiology. However, the leading consequences of the same may vary from case to case. Tumour, in this context, is a special type of pathology which deforms brain parenchyma permanently. From translational perspective, deformation mechanics and pressures, specifically the intracranial cerebral pressure (ICP) in a tumour-housed brain, have not been addressed holistically in literature. This is an important area to investigate in neuropathy prognosis. To address this, we aim to solve the pressure mystery in a tumour-based brain in this study and present a fairly workable methodology. Using image-based finite-element modelling, we reconstruct a tumour-based brain and probe resulting deformations and pressures (ICP). Tumour is grown by dilating the voxel region by 16 and 30 mm uniformly. Cumulatively three cases are studied including an existing stage of the tumour. Pressures of cerebrospinal fluid due to its flow inside the ventricle region are also provided to make the model anatomically realistic. Comparison of obtained results unequivocally shows that as the tumour region increases its area and size, deformation pattern changes extensively and spreads throughout the brain volume with a greater concentration in tumour vicinity. Second, we conclude that ICP pressures inside the cranium do increase substantially; however, they still remain under the normal values (15 mmHg). In the end, a correlation relationship of ICP mechanics and tumour is addressed. From a diagnostic purpose, this result also explains why generally a tumour in its initial stage does not show symptoms because the required ICP threshold has not been crossed. We finally conclude that even at low ICP values, substantial deformation progression inside the cranium is possible. This may result in plastic deformation, midline shift etc. in the brain

Analysis of Growing Tumor on the Flow Velocity of Cerebrospinal Fluid in Human Brain Using Computational Modeling and Fluid-Structure Interaction

Cerebrospinal fluid (CSF) plays a pivotal role in normal functioning of Brain. Intracranial compartments such as blood, brain and CSF are incompressible in nature. Therefore, if a volume imbalance in one of the aforenoted compartments is observed, the other reaches out to maintain net change to zero. Whereas, CSF has higher compliance over long term. However, if the CSF flow is obstructed in the ventricles, this compliance may get exhausted early. Brain tumor on the other hand poses a similar challenge towards destabilization of CSF flow by compressing any section of ventricles thereby ensuing obstruction. To avoid invasive procedures to study effects of tumor on CSF flow, numerical-based methods such as Finite element modeling (FEM) are used which provide excellent description of underlying pathological interaction. A 3D fluid-structure interaction (FSI) model is developed to study the effect of tumor growth on the flow of cerebrospinal fluid in ventricle system. The FSI model encapsulates all the physiological parameters which may be necessary in analyzing intraventricular CSF flow behavior. Findings of the model show that brain tumor affects CSF flow parameters by deforming the walls of ventricles in this case accompanied by a mean rise of 74.23% in CSF flow velocity and considerable deformation on the walls of ventricles

Reliability of Using Elastic Modulus for Non-Homogeneous Materials

This paper investigates the literature available for derivation of the elastic modulus (E) as employed specifically in non-homogenous materials. There is a big pool of E-values in the literature which user can pick and use. However their reliability is still a question. This study will therefore focus on the values of elastic modulus acquired from the secondary databases and their reliability in numerical methods like Finite Elements (FE). This study uses E-values obtained from bones, muscles and tissues. Bone is a composite material with a very intricate internal geometry. Acquiring the elastic modulus values for irregular geometries like bones is not a straight forward process. This study therefore compares the different studies provided in literature for derivation of elastic properties of bones from different vertebrates and investigates the reason of variations. The study infers that populating all the values of elastic modulus without a standard procedure, creates a level of ambiguity that bars the understanding of the use of modulus of elasticity where insightful procedures are in question for example finite element analysis of sensitive materials . Therefore there is a need to take great care in deriving the values of E

Levels of detail analysis of microwave scattering from human head models for brain stroke detection

In this paper, we have presented a microwave scattering analysis from multiple human head models. This study incorporates different levels of detail in the human head models and its effect on microwave scattering phenomenon. Two levels of detail are taken into account; (i) Simplified ellipse shaped head model (ii) Anatomically realistic head model, implemented using 2-D geometry. In addition, heterogenic and frequency-dispersive behavior of the brain tissues has also been incorporated in our head models. It is identified during this study that the microwave scattering phenomenon changes significantly once the complexity of head model is increased by incorporating more details using magnetic resonance imaging database. It is also found out that the microwave scattering results match in both types of head model (i.e., geometrically simple and anatomically realistic), once the measurements are made in the structurally simplified regions. However, the results diverge considerably in the complex areas of brain due to the arbitrary shape interface of tissue layers in the anatomically realistic head model. After incorporating various levels of detail, the solution of subject microwave scattering problem and the measurement of transmitted and backscattered signals were obtained using finite element method. Mesh convergence analysis was also performed to achieve error free results with a minimum number of mesh elements and a lesser degree of freedom in the fast computational time. The results were promising and the E-Field values converged for both simple and complex geometrical models. However, the E-Field difference between both types of head model at the same reference point differentiated a lot in terms of magnitude. At complex location, a high difference value of 0.04236 V/m was measured compared to the simple location, where it turned out to be 0.00197 V/m. This study also contributes to provide a comparison analysis between the direct and iterative solvers so as to find out the solution of subject microwave scattering problem in a minimum computational time along with memory resources requirement. It is seen from this study that the microwave imaging may effectively be utilized for the detection, localization and differentiation of different types of brain stroke. The simulation results verified that the microwave imaging can be efficiently exploited to study the significant contrast between electric field values of the normal and abnormal brain tissues for the investigation of brain anomalies. In the end, a specific absorption rate analysis was carried out to compare the ionizing effects of microwave signals to different types of head model using a factor of safety for brain tissues. It is also suggested after careful study of various inversion methods in practice for microwave head imaging, that the contrast source inversion method may be more suitable and computationally efficient for such problems

Effect of using different types of methods for the derivation of elastic modulus of bone - A critical survey:2017 International Conference on Mechanical, Aeronautical and Automotive Engineering (ICMAA 2017)

The purpose of this paper is to critically review and address the cause of variation in the values of elastic modulus (E) of bone. Properties used for materials (especially) bones is one of the crucial factors in modeling and simulation experiments with sensitive procedures such as Finite Elements. The values of elastic modulus acquired from secondary databases, literature and online repositories differ in many ways. This is due to an underlying fact that different methods are used for one definite set of species and vice versa. According to a human understanding, this might bar the perceptive of use of elastic modulus in the research when (especially) insightful procedures are in question for example Finite Element Analysis (FEA) of materials with sensitive procedures. The means and the methods, through which the values are obtained, do not follow a standard methodology. Thus, this area needs attention. Despite the advances in technology and state-of-the-art methods in the field of biomechanics and biomedical engineering there is a need to formulate a standard method which can produce reliable set of E-values. Through this paper, we seek to raise an important scientific question as to what systemic methodology should be adapted to achieve a value of elastic modulus that is not only reliable, but reasonable as well. The paper also, focus briefly on the sources of error responsible for this variation and the significance of elastic modulus values in important numerical methods such as Finite Elements (FE)

Effect of using different types of methods for the derivation of elastic modulus of bone - A critical survey

The purpose of this paper is to critically review and address the cause of variation in the values of elastic modulus (E) of bone. Properties used for materials (especially) bones is one of the crucial factors in modeling and simulation experiments with sensitive procedures such as Finite Elements. The values of elastic modulus acquired from secondary databases, literature and online repositories differ in many ways. This is due to an underlying fact that different methods are used for one definite set of species and vice versa. According to a human understanding, this might bar the perceptive of use of elastic modulus in the research when (especially) insightful procedures are in question for example Finite Element Analysis (FEA) of materials with sensitive procedures. The means and the methods, through which the values are obtained, do not follow a standard methodology. Thus, this area needs attention. Despite the advances in technology and state-of-the-art methods in the field of biomechanics and biomedical engineering there is a need to formulate a standard method which can produce reliable set of E-values. Through this paper, we seek to raise an important scientific question as to what systemic methodology should be adapted to achieve a value of elastic modulus that is not only reliable, but reasonable as well. The paper also, focus briefly on the sources of error responsible for this variation and the significance of elastic modulus values in important numerical methods such as Finite Elements (FE)