Fractional Flow Reserve in the Femoral Arteries Derived through Computational Fluid Dynamics: A Non-Invasive Diagnostic Tool for Stenotic Diseases [Poster]

Skopalik, S., Paul, M.C. , Radjenovic, A. , Roditi, G., Barrientos, P. H., Matthews, J., Mark, P. and Stuart, W. (2018) Fractional Flow Reserve in the Femoral Arteries Derived through Computational Fluid Dynamics: A Non-Invasive Diagnostic Tool for Stenotic Diseases [Poster]. Society for Magnetic Resonance Angiography 30th Annual Conference (SMRA 2018), Glasgow, UK, 29-31 Aug 2018.

Abstract

Introduction: Fractional flow reserve (FFR) is considered to be the current “gold standard” for assessing the severity of coronary stenotic diseases [1], however it is not yet tested at assessing diseases in other arteries. FFR is the ratio between the maximum achievable blood flow in a stenotic artery and the theoretical maximum achievable blood flow in the same artery in the absence of stenosis, during maximum hyperaemia [2]. Furthermore FFR measurement is costly and is associated with certain risks: it requires drug administration, specialist equipment, an operating room and a medical team [3]. Nevertheless, FFR is a good and relatively simple index of predicting the severity of a stenosis which makes it desirable to test this principle in other vessels, such as the femoral arteries. Purpose Computational fluid dynamics (CFD) combined with high quality medical imaging data can be a viable alternative to catheter derived pressure measurements for FFR calculation. In addition CFD analysis can be useful in predicting blood flow conditions and stenosis severity in a wider range of blood vessels in which catheter measurement may not be possible. To test this, in-silico measurement of FFR in femoral arteries has been the main focus of this study. The use of primarily open-source software has also been identified as one of the goals of the study to reduce diagnostic costs. Method: The method starts with a 3D DICOM vascular dataset of the patient in which the blood vessels of interest are identified and a surface model is generated as shown in Figure 1(a) using VMTK (www.vmtk.org). A 3D computational mesh is then generated and imported into a CFD software STAR-CCM+ (Siemens PLM, 2017) or OpenFoam (https://www.openfoam.com/), where simulations are performed with varying boundary conditions. Blood is modelled as a Newtonian fluid with density of 1060 kg/m3 and dynamic viscosity of 4 mPa·s [4]. Velocity is defined at the inlet and pressure is set at the outlet. Steady state (constant velocity) and transient (pulsatile) boundary conditions were tested. Results and Discussion: Figure 1(b) shows velocity plots on a cut surface plane though the model. Velocity profiles obtained from CFD appear realistic. Inspection of the pressure field, however, shows that it is strongly dependent on the boundary conditions. For example appropriate model needs to be used to take into account the rest of the cardiovascular system which is not otherwise represented in the 3D model. Furthermore, parameters such as vessel length, number of outlets and proximity of the outlets to the inlet also showed to have an influence on the pressure field. This emphasised that in order to use CFD derived FFR as a reliable diagnostic measure, special care needs to be taken when choosing the boundary conditions. Therefore further studies will seek to establish the optimal type of boundary conditions, with special focus on patient specific values, as well as to apply the method to a wider range of vessels.

• Item Type: Conference or Workshop Item
• Status: Published
• Refereed: Yes
• Glasgow Author(s) Enlighten ID: Paul, Professor Manosh and Skopalik, Simeon
• Authors: Skopalik, S., Paul, M.C., Radjenovic, A., Roditi, G., Barrientos, P. H., Matthews, J., Mark, P., and Stuart, W.
• College/School: College of Science and Engineering > School of Engineering > Systems Power and Energy