Experimental and computational investigation of the patient-specific abdominal aortic aneurysm pressure field.

The objective of the present manuscript is three-fold: (i) to study the detailed pressure field inside a patient-specific abdominal aortic aneurysm (AAA) model experimentally and numerically and discuss its clinical relevance, (ii) to validate a number of possible numerical model options and their ability to predict the experimental pressure field and (iii) to compare the spatial pressure drop in the AAA before and after the formation of intraluminal thrombus (ILT) for a late disease development timeline. A finite volume method was used to solve the governing equations of fluid flow to simulate the flow dynamics in a numerical model of the AAA. Following our patient-specific anatomical rapid prototyping technique, physical models of the aneurysm were created with seven ports for pressure measurement along the blood flow path. A flow loop operating with a blood analogue fluid was used to replicate the patient-specific flow conditions, acquired with phase-contrast magnetic resonance imaging, and measure pressure in the flow model. The Navier-Stokes equations and two turbulent models were implemented numerically to compare the pressure estimations with experimental measurements. The relative pressure difference from experiments obtained with the best performing model (unsteady laminar simulation) was ∼1.1% for the AAA model without ILT and ∼15.4% for the AAA model with ILT (using Reynolds Stress Model). Future investigations should include validation of the 3D velocity field and wall shear stresses within the AAA sac predicted by the three numerical models.

New power loss optimized Fontan connection evaluated by calculation of power loss using high resolution PC-MRI and CFD.

A new blood vessel configuration was invented to optimize blood flow efficiency and reduce the power loss in the Fontan connection. The current preferred Fontan configuration, the total cavopulmonary connection (TCPC), usually connects the venae cava (VC) to the pulmonary arteries (PA), bypassing the right ventricle. The new connection, called OptiFlo, has two vertical inlets, which both bifurcate then merge into one another to form two horizontal outlets. One of the preliminary configurations of the new OptiFlo model was used for a comparison experiment between computational fluid dynamics (CFD) and high resolution phase contrast magnetic resonance imaging (PC-MRI) with a voxel resolution of 0.23 mmx0.23 mmx0.25 mm. The thin slice thickness was achieved using the ACGI interpolation technique we have used in other applications before. The 2D PC-MRI velocity vectors were mapped into a CFD grid, enabling direct CFD and MRI data comparisons. The mean squared difference was found between the two dataset Using the viscous power dissipation function we calculated the power loss for both CFD and MRI data. The power losses, calculated with the viscous power dissipation function, were 0.66 mW for CFD and 0.46 mW for the PC-MRI data.