The aim of this study is to assess how the shape of the abdominal aortic aneurysms (AAA) affects the hemodynamic wall stresses. With this purpose, different AAAs are studied through simplified models based on geometrical parameters of the aneurism such as its maximum and minimum diameter, length and asymmetry. Then, a computational fluid dynamics analysis is performed on the simplified models in order to compute pressure and wall shear stresses on the aneurysm sac. The results obtained show that blood pressure is the main dynamic load acting on the artery wall, and that the morphology of the aneurysm could be a good indicator of risk of failure. Furthermore, the computational results are compared with patient-specific real models with the objective to assess the reliability of the proposed simplified approach. (C) 2013 CIMNE (Universitat Politecnica de Catalunya). Published by Elsevier Espana, S.L.U. All rights reserved.

More and more the continuum of care is replacing the traditional way of treating the subjects of care putting people in the centre of the healthcare process. Currently clinicians start treatment after a problem occurs due to the low adoption of Clinical Decision Support Systems (CDSS) integrated with standardised Electronic Health Record (EHR) systems; The volume to value revolution in the healthcare (from stakeholder-centric to patient-centric) will allow doctors to follow the evolution of the individual before a medical episode happens, treating the patient based on statistical trends to forecast the future. The CDSS techniques applied on tele-monitoring tools permit the doctors to predict forthcoming events, improve the diagnosis and avoid continuous visits to the hospital, therefore saving costs. Advanced Medical Expert Support Tool is a step towards achieving the patient-centric approach by incorporating the health information into the EHR using European standards (ISO/EN 13606) to provide semantic interoperability by means of the dual model approach (reference model and archetypes). Three different CDSS modules have been implemented and contextualised publications are provided to the cardiologist to facilitate their daily work. A person-centric Graphical User Interface (GUI) facilitates the visualization of the health status of the patients providing meaningful information to the cardiologists. The use of archetypes allows scalability, transparency and efficiency to the hospital environment.

Time-resolved, 3-dimensional phase-contrast magnetic resonance imaging (3D+t PCMRI) is employed to obtain complete spatial and temporal coverage of the vessels blood combined with spatially registered 3-directional pulsatile blood flow velocities[1][2]. Recent studies have reported that Wall Shear Stress (WSS) quantification from PCMRI are able to use the WSS as biomarkers for different aortas pathologies [3]. Figure [1] shows the pathline visualization of blood flow during one cardiac cycle in the heart of a healthy patient at peak early LV filling, diastasis, peak atrial contraction, and peak systole.

The objective of this study is to find a correlation between the abdominal aortic aneurysm (AAA) geometric parameters, wall stress shear (WSS), abdominal flow patterns, intraluminal thrombus (ILT), and AAA arterial wall rupture using computational fluid dynamics (CFD). Real AAA 3D models were created by three-dimensional (3D) reconstruction of in vivo acquired computed tomography (CT) images from 5 patients. Based on 3D AAA models, high quality volume meshes were created using an optimal tetrahedral aspect ratio for the whole domain. In order to quantify the WSS and the recirculation inside the AAA, a 3D CFD using finite elements analysis was used. The CFD computation was performed assuming that the arterial wall is rigid and the blood is considered a homogeneous Newtonian fluid with a density of 1050 kg/m 3 and a kinematic viscosity of4×10-3Pa·s. Parallelization procedures were used in order to increase the performance of the CFD calculations. A relation between AAA geometric parameters (asymmetry index ( β ), saccular index ( γ ), deformation diameter ratio ( χ ), and tortuosity index ( ε )) and hemodynamic loads was observed, and it could be used as a potential predictor of AAA arterial wall rupture and potential ILT formation.

An aortic dissection (AD) is a serious condition defined by the splitting of the arterial wall, thus generating a secondary lumen [the false lumen (FL)]. Its management, treatment and follow-up are clinical challenges due to the progressive aortic dilatation and potentially severe complications during follow-up. It is well known that the direction and rate of dilatation of the artery wall depend on haemodynamic parameters such as the local velocity profiles, intra-luminal pressures and resultant wall stresses. These factors act on the FL and true lumen, triggering remodelling and clinical worsening. In this study, we aimed to validate a computational fluid dynamic (CFD) tool for the haemodynamic characterisation of chronic (type B) ADs. We validated the numerical results, for several dissection geometries, with experimental data obtained from a previous in vitro study performed on idealised dissected physical models. We found a good correlation between CFD simulations and experimental measurements as long as the tear size was large enough so that the effect of the wall compliance was negligible.

Aortic Coarctation is a congenital constriction of the aorta that increases blood pressure above the constriction and hinders the flow below it. Based on a 3D surface mesh of a moderate thoracic coarctation, a high quality volume mesh is created using an optimal tetrahedral aspect ratio for whole domain. In order to quantify the severity of this constriction, a coupled 1D lumped-parameter/3D CFD approach is used to calculate the pressure drop through the coarctation. The CFD computation is performed assuming that the arterial wall is rigid and the blood is considered a homogeneous Newtonian fluid with density r = 0.001 gr/mm3 and a dynamic viscosity m = 0.004 gr/mm/sec in laminar flow. The boundary conditions of the 3D model (inlet and outlet conditions) have been calculated using a 1D model. Parallelization procedures will be used in order to increase the performance of the CFD calculations.

Delayed Enhancement Magnetic Resonance Imaging can be used to non-invasively differentiate viable from non-viable myocardium within the Left Ventricle in patients suffering from myocardial diseases. Automated segmentation of scarified tissue can be used to accurately quantify the percentage of myocardium affected. This paper presents a method for cardiac scar detection and segmentation based on supervised learning and level set segmentation. First, a model of the appearance of scar tissue is trained using a Support Vector Machines classifier on image-derived descriptors. Based on the areas detected by the classifier, an accurate segmentation is performed using a segmentation method based on level sets.

An experimental investigation was undertaken to study the characteristics of curved turbulent water jets produced from a vertical slot diffuser with sharp protrusions at the exit plane. The experiments were performed at two different flow rates for which the Reynolds number based on slot width and average velocity were 2050 and 4100. A high resolution particle image velocimetry system was used to perform detailed velocity measurements which were post-processed to obtain the mean velocities, Reynolds stresses and turbulence kinetic energy. The decay of the centerline mean velocity and jet half-width were also obtained to evaluate the mixing characteristics of the present slot configuration vis-à-vis results reported in previous studies. It was observed that the mixing characteristics of the slot configuration investigated in this study are superior to most of the sharp-edged nozzle configurations and curved jets studied in the past. The effects of streamline curvature on the Reynolds stresses in the convex and concave regions were also examined. The results clearly demonstrated that streamline curvature significantly enhanced the level of the streamwise turbulence intensity in the convex region more than in the concave region. On the contrary, the Reynolds shear stress and transverse turbulence intensity are much larger in the concave region than in the convex region. These results, together with the distributions of the Reynolds stress ratios across the jet, provide clear indications that turbulence models that assume local equilibrium and isotropy will not be able to accurately reproduce the flow characteristics of curved turbulent jets.

Obstructive sleep apnea syndrome (OSAS) consists in the occurrence of recurrent episodes of airflow limitation during sleep, with undesirable consequences for the health. The phenomenon is well known from a medical point of view (prognosis, diagnosis and treatment), but there is not a methodology or analysis tools for the quantification of the clinical response using Mandibular Advancement Devices (MAD). This paper shows how combining image processing, fluid dynamics and engineering design criteria, imported from other fields, allow to establish a simple analysis method clinically useful to decide the more convenient positioning of the MAD based on the pressure or mechanical movement of the jaw. This methodology is applied to a patient suffering OSAS which the objective to evaluate the changes provoked in the upper-airways due to an innovative mandibular device. (C) 2011 CIMNE (Universitat Politecnica de Catalunya). Published by Elsevier Espana, S.L. All rights reserved.

To deal with the large amount of data produced by telemonitoring of patients with chronic diseases, a decision support system (DSS) was developed. The DSS uses sensor data and the data from a patient’s electronic health record as the input. It assesses the risk to the patient’s health using three approaches. The first approach exploits the existing medical knowledge, the second approach uses supervised machine learning, and the third approach simply detects anomalies in the values of the monitored parameters. The risk assessment can show the contribution of the individual monitored parameters to the risk, and can be tailored by the doctor to each patient. The assessed risk and the raw input data can be used to trigger alerts. Finally, following the principles of evidence-based medicine, the DSS facilitates the consultation of medical literature when needed.

Medical imaging techniques, such as MRI and CT scanning, are valuable tools for getting a lot of information non-invasively and it is useful for reconstructing the geometry of complex objects about the patients. Medical-GiD is a medical image platform that incorporates a module to read directly the blood velocity profile from the MR scan, in particular for deformable registration of 4D MRI images, Electrocardiography (ECG)-synchronized and respiration controlled 3D magnetic resonance (MR) velocity mapping (flow-sensitive 4D MRI), 3D morphologic and three-directional blood flow data. Furthermore, Medical-GiD is focus in the medical image processing in the biomechanical research field to generating meshes from the medical images, to apply in Computational Fluid Dynamics (CFD) or structural mechanics (stress analysis). To date, these techniques have largely been applied to compute meshes for numerical simulations, but with Medical-GiD, we will have the integration between the real data and numerical simulations.

The management and follow-up of chronic type B aortic dissections continues being a clinical challenge. Patients with chronic type B dissection have high mid/long term mortality mainly due to progressive aortic dilatation and subsequent rupture. To predict further dilatation, guidelines suggest follow-up of the total aortic diameter. However, dilatation is triggered by haemodynamic parameters (intra-luminal pressure and flow conditions/wall shear stresses), and geometric factors such as the communication between false (FL) and true lumen (TL). The aim of this study is to assess whether TL and FL haemodynamics and its determinants (such as the tear size, location and number) will allow us to define risk markers of further aortic enlargement. For this, we performed in-silico studies on idealized dissected aortic geometries. A type B aortic dissection was created in which FL has double the diameter of TL. Three different circular tear configurations are studied: only a 10 mm proximal tear, and a 10 mm proximal tear with either a 4 mm or a 10 mm distal tear. Resulting flow volume, pressure, and wall shear stress (WSS) profiles of TL and FL were analyzed. Preliminary results show that the presence of an adequate outflow in the distal tear is associated with an important increase in diastolic pressure and wall stress and diastolic retrograde flow, putting FL at high risk for dilatation. We have constructed a model of a type B dissection which allows studying dissected anatomic configurations and their resulting haemodynamics. It is expected that in-silico models will show the influence of tear configuration, thus providing ways for a better understanding of the haemodynamic conditions, as observed in clinical practice, and related evolution in patients with a chronic aortic dissection.

Management and follow-up of chronic aortic dissections continues to be a clinical challenge due to progressive aortic dilatation. To predict dilatation, guidelines suggest follow-up of the aortic diameter. However, dilatation is triggered by haemodynamic parameters (pressure and wall shear stresses (WSS)), and geometry of false (FL) and true lumen (TL). We aimed at a better understanding of TL and FL haemodynamics by performing in-silico (CFD) and in-vitro studies on an idealized dissected aorta and compared this to a typical patient. We observed an increase in diastolic pressure and wall stress in the FL and the presence of diastolic retrograde flow. The inflow jet increased WSS at the proximal FL while a large variability in WSS was induced distally, all being risk factors for wall weakening. In-silico, in-vitro and in-vivo findings were very similar and complementary, showing that their combination can help in a more integrated and extensive assessment of aortic dissections, improving understanding of the haemodynamic conditions and related clinical evolution.

Predict the evolution of the rupture in Chronic Aortic Dissection poses a cardiovascular challenge. Several parameters must be studied to determinate this evolution, in any cases is demonstrated that dilatation is triggered by fluid-dynamic parameters (intraluminal pressure and wall shear stresses) and physiological vessel wall properties, but these hemodynamic factors are really important in the final evolution of the aortic dissection. In order to improve the behaviour and the development of different cases of chronic dissection, is needed a better understanding of pressure and velocity influence on the false lumen (FL) and true lumen(TL) of the vessel, including the study of different scenarios of entry and exit tears. For this reason, we have performed FEM analysis in a typical aortic dissection, closely resembling clinical practice (Stanford B or Type III DeBakey dissection1). The aortic dissection was created with a FL had double diameter of the TL. Different entry and exit tear configurations were studied: only entry, only exit and equally sized entry and exit tears. A three dimensional computational fluid dynamics simulation (using a pres-postprocessor software environment) of the cardiac cycle was performed. Velocity, Shear Stress and pressure profiles were analyzed in the TL and FL and all along the geometry with GiD tools.

Vascular diseases are very common, nowadays, especially as people age, due to bad eating habits and physical inactivity, among other causes. This fact is very important because this problem trends to grow up quickly, especially in industrialized countries. New kinds of surgical techniques use to detect and treat vascular diseases, every day, micro- invasive approaches, like endo-surgery, endoscopy and catheterism. Medical solutions like stent applications, substitutions of cardiac valvulas use today these innovative techniques. Due to this fact the study of the materials used in these devices becomes an important matter. GiD gives the possibility to design and study through different problems type's devices that can be used to solve problems like these. The object of this work is to model and analyze with GiD and with the thermo-mechanical computational code COMET an intravascular metallic support that can be compressed until the right dimension is reached, so it can be inserted via- catheter in situ. The decompression of the device is of primary importance because every plastic deformation can interests the final disposition of the support and it could change its properties and the capacity to perform properly. This investigation will focus in the study of the forces implied and the effects on the device material. Also the different behaviour of various bio-materials like Steel, Titanium and Nitinol are studied. This study can help to find the best configuration for this kind of devices.