Blood Flow Modeling in Carotid Arteries with Computational Fluid Dynamics and MR Imaging 1 Juan R. Cebral, PhD, Peter J. Yim, PhD, Rainald Lo ¨ hner, PhD, Orlando Soto, PhD, Peter L. Choyke, MD Rationale and Objectives. The authors’ goal was to develop a noninvasive method for detailed assessment of blood flow patterns from direct in vivo measurements of vessel anatomy and flow rates. Materials and Methods. The authors developed a method to construct realistic patient-specific finite element models of blood flow in carotid arteries. Anatomic models are reconstructed from contrast material– enhanced magnetic resonance (MR) angiographic images with a tubular deformable model along each arterial branch. A surface-merging algorithm is used to create a watertight model of the carotid bifurcation for subsequent finite element grid generation, and a fully im- plicit scheme is used to solve the incompressible Navier-Stokes equations on unstructured grids. Physiologic boundary conditions are derived from cine phase-contrast MR flow velocity measurements at two locations below and above the bifurcation. Vessel wall compliance is incorporated by means of fluid-solid interaction algorithms. Results. The method was tested on imaging data from a healthy subject and a patient with mild stenosis. Finite element grids were successfully generated, and pulsatile blood flow calculations were performed. Computed and measured velocity profiles show good agreement. Flow patterns and wall shear stress distributions were visualized. Conclusions. Patient-specific computational fluid dynamics modeling based on MR images can be performed robustly and efficiently. Preliminary validation studies in a physical flow-through model suggest that the model is accurate. This method can be used to characterize blood flow patterns in healthy and diseased arteries and may eventually help physi- cians to supplement imaging-based diagnosis and predict and evaluate the outcome of interventional procedures. Key Words. Carotid arteries, flow dynamics; carotid arteries, MR; carotid arteries, stenosis or obstruction; magnetic reso- nance (MR), vascular studies. © AUR, 2002 Atherosclerotic disease of the carotid artery is a leading cause of stroke (1). Atherosclerotic plaque in the carotid artery obstructs blood flow to the brain and stimulates the formation of thromboemboli that occlude downstream vessels. Unusual shear stress patterns and disturbed flows are related to plaque rupture, plaque erosion, and the for- mation of thromboemboli. The risk of stroke from carotid artery stenosis progressively increases with increasing degree of stenosis, but the degree of stenosis does not completely explain stroke risk; moderate carotid artery stenosis is associated with stroke, though not quite as strongly as high-grade stenosis (2,3). Given the well-recognized predisposition to atheroscle- rotic plaque formation of specific arterial regions with curvature, such as the carotid bifurcation, hemodynamics and arterial geometry may both offer useful information for carotid artery stenosis evaluation (4,5). The local he- modynamics and consequently the wall shear stress are strongly influenced by the morphologic characteristics of the stenosis (6) and the flow waveforms (7). Furthermore, to date there are no reliable methods to determine wall Acad Radiol 2002; 9:1286–1299 1 From the School of Computational Sciences, George Mason University, 4400 University Dr, MSN 4C7, Fairfax, VA 22030 (J.R.C., R.L., O.S.); and the Imaging Science Program, National Institutes of Health, Bethesda, Md (P.J.Y., P.L.C.). Received July 16, 2002; accepted July 30. Address corre- spondence to J.R.C. © AUR, 2002 1286