0
Technical Briefs

Targeted Particle Tracking in Computational Models of Human Carotid Bifurcations

[+] Author and Article Information
Ian Marshall

Medical Physics and Medical Engineering,  University of Edinburgh, Chancellor’s Building, 49 Little France Crescent, Edinburgh, EH16 5SB, UK, e-mail: ian.marshall@ed.ac.uk

J Biomech Eng 133(12), 124501 (Dec 21, 2011) (5 pages) doi:10.1115/1.4005470 History: Received November 02, 2010; Revised November 18, 2011; Published December 21, 2011; Online December 21, 2011

A significant and largely unsolved problem of computational fluid dynamics (CFD) simulation of flow in anatomically relevant geometries is that very few calculated pathlines pass through regions of complex flow. This in turn limits the ability of CFD-based simulations of imaging techniques (such as MRI) to correctly predict in vivo performance. In this work, I present two methods designed to overcome this filling problem, firstly, by releasing additional particles from areas of the flow inlet that lead directly to the complex flow region (“preferential seeding”) and, secondly, by tracking particles both “downstream” and “upstream” from seed points within the complex flow region itself. I use the human carotid bifurcation as an example of complex blood flow that is of great clinical interest. Both idealized and healthy volunteer geometries are investigated. With uniform seeding in the inlet plane (in the common carotid artery (CCA)) of an idealized bifurcation geometry, approximately half the particles passed through the internal carotid artery (ICA) and half through the external carotid artery. However, of those particles entering the ICA, only 16% passed directly through the carotid bulb region. Preferential seeding from selected regions of the CCA was able to increase this figure to 47%. In the second method, seeding of particles within the carotid bulb region itself led to a very high proportion (97%) of pathlines running from CCA to ICA. Seeding of particles in the bulb plane of three healthy volunteer carotid bifurcation geometries led to much better filling of the bulb regions than by particles seeded at the inlet alone. In all cases, visualization of the origin and behavior of recirculating particles led to useful insights into the complex flow patterns. Both seeding methods produced significant improvements in filling the carotid bulb region with particle tracks compared with uniform seeding at the inlet and led to an improved understanding of the complex flow patterns. The methods described may be combined and are generally applicable to CFD studies of fluid and gas flow and are, therefore, of relevance in hemodynamics, respiratory mechanics, and medical imaging science.

FIGURES IN THIS ARTICLE
<>
Copyright © 2011 by American Society of Mechanical Engineers
Your Session has timed out. Please sign back in to continue.

References

Figures

Grahic Jump Location
Figure 3

Calculated pathlines in computational models of carotid bifurcations of three healthy young volunteers. The ICA is shown on the left. (a)–(c) Volunteer 1. (d)-(f) Volunteer 2. (g)-(i) Volunteer 3. The first column ((a), (d), and (g)) shows pathlines of 300 of 10,000 particles released with uniform distribution in the inlet plane, colored blue if exiting through the ICA and red if exiting through the ECA. Paths exhibiting recirculation are colored black regardless of exit vessel. Alongside are shown cross sectional images at the inlet plane and at the carotid bulb plane (identified with horizontal black line) for all 10,000 particles. Particles in the inlet plane are colored as for the pathlines. Recirculating particles in the bulb plane are colored yellow on first pass antegrade flow, black on second pass retrograde flow, and gray on third pass antegrade flow. The second column ((b), (e), and (h)) as for first column but for 10,000 particles released with uniform distribution in the bulb plane. The third column ((c), (f), and (i)) shows the combination of pathlines from the first two columns.

Grahic Jump Location
Figure 1

(a) Calculated pathlines for every tenth of 10,000 particles of Group 1 released with uniform distribution in the inlet plane of an idealized carotid bifurcation model. The ICA is shown on the left. The “carotid bulb plane” is identified by the colored horizontal line. Circulatory flow and sparse filling are clearly visible in the “carotid bulb region” (defined as the outer half of the internal carotid artery (ICA) at the level of the bulb plane, and colored orange). Alongside are shown cross sectional images at the inlet plane in the common carotid artery (CCA) and at the carotid bulb plane for all 10,000 particles. Particles are shaded according to the position at which they first pass through the bulb plane with antegrade flow (magenta for ECA, green for ICA, and orange for the bulb region). (b) Group 2 and (c) Group 3: as for (a), but particles were released with uniform distribution over the subregions in the CCA inlet plane as shown, in order to target the carotid bulb region. (d) The combination of all 30,000 particles of Groups 1–3. For clarity, only 500 pathlines are shown for each group. Particles in the cross-sectional images are colored according to the lateral position at which they first pass through the bulb plane (first pass antegrade flow), ranging from orange (in the bulb region of the ICA) through yellow, green, and blue to red (in the outer part of the ECA). Particles undergoing recirculation pass downwards through the recirculation region in the carotid bulb (second pass retrograde flow: shaded black) before third pass antegrade flow through the bulb plane (shaded gray) and finally exit the model through the ICA. See also Table 1.

Grahic Jump Location
Figure 2

(a) Calculated pathlines for every tenth of 10,000 particles (Group 5) released with uniform distribution in the bulb plane of the ICA (identified by the horizontal black line) of an idealized carotid bifurcation model. Note the excellent filling of most of the bulb region. (b) The combination of Groups 1 (see Fig. 1a) and 5 led to adequate filling of most of the carotid model.

Tables

Errata

Discussions

Some tools below are only available to our subscribers or users with an online account.

Related Content

Customize your page view by dragging and repositioning the boxes below.

Related Journal Articles
Related eBook Content
Topic Collections

Sorry! You do not have access to this content. For assistance or to subscribe, please contact us:

  • TELEPHONE: 1-800-843-2763 (Toll-free in the USA)
  • EMAIL: asmedigitalcollection@asme.org
Sign In