A CFD and FEM Approach to a Multicompartmental Poroelastic Model for CSF Production and Circulation with Applicationsin Hydrocephalus Treatment and Cerebral Oedema

This paper was presented at the 4th Micro and Nano Flows Conference (MNF2014), which was held at University College, London, UK. The conference was organised by Brunel University and supported by the Italian Union of Thermofluiddynamics, IPEM, the Process Intensification Network, the Institution of Mechanical Engineers, the Heat Transfer Society, HEXAG - the Heat Exchange Action Group, and the Energy Institute, ASME Press, LCN London Centre for Nanotechnology, UCL University College London, UCL Engineering, the International NanoScience Community, www.nanopaprika.eu.This study introduces a Multiple-Network Poroelastic Theory (MPET) model, coupled with finite-volume based Computational fluid dynamics (CFD) for the purpose of studying, in detail, the effects of obstructing Cerebrospinal fluid (CSF) transport within an image-derived cerebral environment. The MPET representation allows the investigation of fluid transport between CSF, brain parenchyma and cerebral blood, in an integral and comprehensive manner. Key novelties of this model are the casting of multidimensional MPET in a Finite Element Method (FEM) framework, the amalgamation of anatomically accurate choroid plexuses with their feeding arteries and a simple relationship relaxing the constraint of a unique permeability for the CSF compartment. This model is used to demonstrate the impact of fourth ventricle outlet obstruction (FVOO). The implications of treating such a clinical condition with the aid of endoscopic third (ETV) and endoscopic fourth (EFV) ventriculostomy are considered. Finally, we outline the impact of the FEM based MPET framework in understanding oedema, and its ongoing evolution

A fully dynamic multi-compartmental poroelastic system: Application to aqueductal stenosis

This study proposes the implementation of a fully dynamic four-network poroelastic model which is underpinned by multiple-network poroelastic theory (MPET), in order to account for the effects of varying stages of aqueductal stenosis and atresia during acute hydrocephalus. The innovation of the fully dynamic MPET implementation is that it avoids the commonplace assumption of quasi-steady behaviour; instead, it incorporates all transient terms in the casting of the equations and in the numerical solution of the resulting discrete system. It was observed that the application of mild stenosis allows for a constant value of amalgamated ventricular displacement in under 2.4 h, whereas the application of a severe stenosis delays this settlement to approximately 10 h. A completely blocked aqueduct does not show a clear sign of reaching a steady ventricular displacement after 24 h. The increasing ventricular pressure (complemented with ventriculomegaly) during severe stenosis is causing the trans-parenchymal tissue region to respond, and this coping mechanism is most attenuated at the regions closest to the skull and the ventricles. After 9 h, the parenchymal tissue shows to be coping well with the additional pressure burden, since both ventriculomegaly and ventricular CSF (cerebrospinal fluid) pressure show small increases between 9 and 24 h. Localised swelling in the periventricular region could also be observed through CSF fluid content, whilst dilation results showed stretch and compression of cortical tissue adjacent to the ventricles and skull

Investigating cerebral oedema using poroelasticity

Cerebral oedema can be classified as the tangible swelling produced by expansion of the interstitial fluid volume. Hydrocephalus can be succinctly described as the abnormal accumulation of cerebrospinal fluid (CSF) within the brain which ultimately leads to oedema within specific sites of parenchymal tissue. Using hydrocephalus as a test bed, one is able to account for the necessary mechanisms involved in the interaction between oedema formation and cerebral fluid production, transport and drainage. The current state of knowledge about integrative cerebral dynamics and transport phenomena indicates that poroelastic theory may provide a suitable framework to better understand various diseases. In this work, Multiple-Network Poroelastic Theory (MPET) is used to develop a novel spatio-temporal model of fluid regulation and tissue displacement within the various scales of the cerebral environment. The model is applied through two formats, a one-dimensional finite difference – Computational Fluid Dynamics (CFD) coupling framework, as well as a two-dimensional Finite Element Method (FEM) formulation. These are used to investigate the role of endoscopic fourth ventriculostomy in alleviating oedema formation due to fourth ventricle outlet obstruction (1D coupled model) in addition to observing the capability of the FEM template in capturing important characteristics allied to oedema formation, like for instance in the periventricular region (2D model)

Poroelastic Modelling of CSF circulation via the incorporation of experimentally derived microscale water transport properties

We outline how multicompartmental poroelasticity is applied to the study of dementia. We utilize a 3D version of our poroelastic code to investigate the effects within parenchymal tissue. This system is coupled with multiple pipelines within the VPH-DARE@IT project which account for patient/subject-specific boundary conditions in the arterial compartment, in addition to both an image segmentation-mesh and integrated cardiovascular system model pipeline respectively. This consolidated template allows for the extraction of boundary conditions to run CFD simulations for the ventricles. Finally, we outline some experimental results that will help inform the MPET system

An ecological approach to problems of Dark Energy, Dark Matter, MOND and Neutrinos

Modern astronomical data on galaxy and cosmological scales have revealed powerfully the existence of certain dark sectors of fundamental physics, i.e., existence of particles and fields outside the standard models and inaccessible by current experiments. Various approaches are taken to modify/extend the standard models. Generic theories introduce multiple de-coupled fields A, B, C, each responsible for the effects of DM (cold supersymmetric particles), DE (Dark Energy) effect, and MG (Modified Gravity) effect respectively. Some theories use adopt vanilla combinations like AB, BC, or CA, and assume A, B, C belong to decoupled sectors of physics. MOND-like MG and Cold DM are often taken as opposite frameworks, e.g. in the debate around the Bullet Cluster. Here we argue that these ad hoc divisions of sectors miss important clues from the data. The data actually suggest that the physics of all dark sectors is likely linked together by a self-interacting oscillating field, which governs a chameleon-like dark fluid, appearing as DM, DE and MG in different settings. It is timely to consider an interdisciplinary approach across all semantic boundaries of dark sectors, treating the dark stress as one identity, hence accounts for several "coincidences" naturally.Comment: 12p, Proceedings to the 6-th Int. Conf. of Gravitation and Cosmology. Neutrino section expande

Investigating Dementia via a multicompartmental poroelastic model of parenchymal tissue

In this paper, a workflow within the VPH-DARE@IT Clinical Research Platform is presented. This is used to model the biomechanical behaviour of perfused brain tissue. This workflow features a 3D multicompartmental poroelastic framework, patient-specific brain anatomy representations and continuous waveforms of internal carotid and vertebral arteries, which are used as a means of personalizing the boundary conditions that feed the arterial compartment of the in-house poroelastic solver. Results are shown comparing CSF/ISF clearance and accumulation in two males of similar age, both are non-smokers, however one is more active and is diagnosed with MCI and experiences less sleep