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

Abstract

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.

Keywords::

• computational fluid dynamics
• aneurysm
• pressure gradient
• pressure tap
• rapid prototyping

Acknowledgements

The authors want to acknowledge the help of Samarth Raut for the initial segmentation of the DICOM images and Onur Dur for his help with the pressure transducer calibration. The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Institutes of Health.

Additional information

Funding

The scholarship was granted by the Spanish Government to R.A. under the ‘José Castillejo’ program and the Antonio Aranzabal Foundation. This work was supported in part by the National Institutes of Health through award 1R15HL087268-01A2 (to EAF).