Background and Purpose-Traditional vascular risk factors do not completely explain the asymmetry, racial, and sex differences in carotid artery disease. Carotid anatomy and geometry may play a role in the pathogenesis of internal carotid artery (ICA) stenosis, but their effects are unknown. We hypothesized that carotid artery anatomy and geometry would be independently associated with ICA stenosis. Method-This is a retrospective study of patients with CT angiography at Monash Medical Centre, 2006 to 2007. Carotid arteries were segmented using semiautomated methods to estimate measures of carotid anatomy and geometry. Measurements of carotid artery geometry were performed according to the recent article by Thomas and colleagues. ICA stenosis was dichotomized as Ͻ30% or Ն30% stenosis. Cluster logistic regression was used to examine the associations of anatomy and geometry with stenosis accounting for the paired arteries within subjects, adjusting for age, sex, and vascular risk factors. Results-Mean age of the sample (nϭ178) was 68.4 years (SD, 14 years). The following were independently associated with ICA stenosis: ICA radius at the bifurcation (OR, 0.20; 95% CI, 0.14 -0.

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Background: Current literature emphasizes the role of the Circle of Willis (CoW) in salvaging ischemic brain tissue but not that of leptomeningeal anastomoses (LA). We developed a computational model of the cerebral circulation to (1) evaluate the roles of the CoW and LA in restoring flow to the superficial compartment of the middle cerebral artery (MCA) territory and (2) estimate the size of the LA required to maintain flow above the critical ischemic threshold (>30% of baseline) under simulated occlusion.Methods: Cerebral vasculature was modeled as a network of junctions connected by cylindrical pipes. The experiments included occlusion of successive distal branches of the intracranial arteries while the diameters of LA were varied.Results: The model showed that the region of reduced flow became progressively smaller as the site of occlusion was moved from the large proximal to the smaller distal arteries. There was no improvement in flow in the MCA territory when the diameters of the inter-territorial LA were varied from 0.0625 to 0.5 mm while keeping the intra-territorial LA constant. By contrast, the diameter of the inter-territorial LA needed to be >1.0 mm in order to provide adequate (>30%) flow to selected arteries in the occluded MCA territory.Conclusion: The CoW and inter-territorial LA together play important supportive roles in intracranial artery occlusion. Computational modeling provides the ability to experimentally investigate the effect of arterial occlusion on CoW and LA function.

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The manner in which food breaks down during mastication directly influences not only perception of texture but also the temporal release of taste and aroma compounds and perception of flavor. Although sampling chewed food during mastication allows local quantitative measurement of particle properties and taste and aroma compound concentrations, it is not possible to measure the full spatiotemporal variations of these quantities. Computational modeling can be used to estimate the values of these quantities throughout the volume of the oral cavity at any point in the chewing cycle or allow controlled parametric analysis that would be impractical in physical experimentation. We present a coupled biomechanical-smoothed particle hydrodynamics model of human mastication and predict the mechanical behavior and breakdown of two agar model foods. The results of these simulations show that our model has the potential to enhance the understanding of the relationship between food structure and oral breakdown during mastication. PRACTICAL APPLICATIONSDevelopment of a computational model of chewing and oral breakdown will enhance the understanding of the relationship between food structure, oral breakdown and flavor release during mastication. A functional model may be utilized to design the material and structural properties of food products that will break down in a desired fashion during chewing. Future model extensions that facilitate the prediction of flavor release given known mechanical properties will facilitate how to add flavor to provide a target sensory profile. This knowledge will fasttrack innovations in new food product development and facilitate reformulation of healthier food products without compromising sensory quality. In the future, the ability to predict the physical and chemical stimuli may facilitate the prediction of sensory perception from first principles.

A dynamic, three dimensional (3D) computational model that predicts the breakdown of food and the release of tastants and aromas could enhance the understanding of how food is perceived during consumption. This model could also shorten the development process of new foods because many virtual foods could be assessed, and discarded if unsuitable, before any physical prototyping is required. The construction and testing of a complete 3D model of mastication presents many challenges including an accurate representation of: the anatomical movements of the oral cavity (including the teeth, tongue, cheeks and palates), the breakdown behaviour of the food, the interactions between comminuted food and saliva as the bolus is formed, the release and transport of taste and aromas and how these physical and chemical processes are perceived by a person. These challenges are discussed in reference to previous experimental and simulation work and using results of new applications of a coupled biomechanical-smoothed particle hydrodynamics (B-SPH) model. The B-SPH model is demonstrated to simulate several complicated aspects of mastication including: (1) the sensitivity of particle size to changes in the movements of the jaw and tongue; (2) large strain behaviour of food due to softening by heating; (3) interactions between solid and liquid food components; (3) the release of tastants into the saliva; and (4) the transport of tastants to the taste buds. These applications show the possibilities of a model to viably simulate mastication, but highlight the many modelling and experimental challenges that remain.