Abstract 20161: Mapping Blood Viscosity Profile onto Magnetic Resonance Angiography Identifies Localized Viscosity Surges Near Regions of Low Wall Shear Stresses
Background: Blood flow is non-Newtonian, and blood viscosity (BV) is a factor in cardiac output, blood flow velocity, and wall shear stress (WSS). Regions of low WSS have been implicated in atherosclerotic plaque progression and rupture.
Aim: To evaluate the feasibility of a new Methodology for mapping BV and WSS onto 3D images of human arteries using subjects' own dynamic BV profiles and flow velocities.
Methods: To simulate patient-specific blood flow, 3D geometries of cerebral arteries were constructed from 2D brain MRA and corresponding computational meshes generated. Boundary conditions for flow simulation included patients' peak-systolic (PS) and end-diastolic (ED) flow velocities measured by transcranial Doppler (TCD) and BV profiles measured continuously over a range of shear using an automated tube viscometer. Distributions for BV, wall normal stress, and WSS were produced by flow simulation and color-mapped on 3D images of 11 middle cerebral arteries (MCAs) from 7 subjects.
Results: Separations in blood flow, i.e., turbulent surges in BV, were defined as > 10% increase in BV than the lowest value in each subject. Such focal areas of increased BV were observed in all 11 MCAs at post-plaque dilated segments and branching sites. Regions of low WSS (i.e., < 4 dyne/cm2) overlapped with BV focal areas in the arteries of the patients, however areas of low WSS regions were 338% larger in size than focal areas of increased BV (median [inter-quartile ranges], 4.1 [0.6∼13.2] vs. 0.8 [0.1∼1.8] mm2, p = 0.039, respectively).
Conclusions: This feasibility study demonstrated successful mapping of a subject's own BV profile onto MRA images. Observations of focal areas of increased BV reflect localized biophysical interactions of blood components with endothelium. In regions of low WSS, there was heterogeneity that exhibited focal increases in BV. However focal areas of increased BV were 338% smaller than areas of low WSS, suggesting greater localization and precision of the BV parameter as compared with WSS. Successful mapping of a subject's vascular shear stress and BV using their own specific shear-dependent BV profile represents a new fluid dynamic biomarker for calculating risk of potential atherosclerotic plaque growth and rupture.
- Cardiovascular imaging
- Blood pressure determination
- Magnetic resonance imaging
- Plaque rupture
- Subclinical atherosclerosis
- © 2010 by American Heart Association, Inc.