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Research Papers

Immersive Visualization for Enhanced Computational Fluid Dynamics Analysis

[+] Author and Article Information
David J. Quam

Department of Biomedical Engineering,
Marquette University,
Milwaukee, WI 53233
e-mail: dj.quam@gmail.com

Timothy J. Gundert

Department of Biomedical Engineering,
Marquette University,
Milwaukee, WI 53233
e-mail: timothy.gundert@gmail.com

Laura Ellwein

Department of Biomedical Engineering,
Marquette University,
Milwaukee, WI 53233
e-mail: laura.ellwein@gmail.com

Christopher E. Larkee

MARquette Visualization Lab (MARVL),
College of Engineering,
Marquette University,
Milwaukee, WI 53233
e-mail: christopher.larkee@marquette.edu

Paul Hayden

Discovery World at Pier Wisconsin,
Milwaukee, WI 53202
e-mail: haydenp@discoveryworld.org

Raymond Q. Migrino

Phoenix VA Health Care System,
Phoenix, AZ 85012
Division of Cardiovascular Medicine,
Medical College of Wisconsin,
Milwaukee, WI 53226
e-mail: Raymond.migrino@va.gov

Hiromasa Otake

Kobe University Graduate School of Medicine,
Kobe, Japan
e-mail: hiro_yuki15@yahoo.co.jp

John F., LaDisa, Jr.

Department of Biomedical Engineering,
Marquette University,
Milwaukee, WI 53233
Director,
MARquette Visualization Lab (MARVL),
Marquette University,
Milwaukee, WI 53233
Director,
Laboratory for Translational,
Experimental and Computational Cardiovascular Research,
Marquette University
Medical College of Wisconsin,
Milwaukee, WI 53233
Division of Cardiovascular Medicine,
Medical College of Wisconsin,
Milwaukee, WI 53233

1Present address: Department of Mathematics and Applied Mathematics, Virginia Commonwealth University, Richmond, VA 23284.

2Corresponding author.

Manuscript received November 22, 2013; final manuscript received August 5, 2014; published online January 29, 2015. Assoc. Editor: Ender A. Finol.

This material is declared a work of the U.S. Government and is not subject to copyright protection in the United States. Approved for public release; distribution is unlimited.

J Biomech Eng 137(3), 031004 (Mar 01, 2015) (12 pages) Paper No: BIO-13-1551; doi: 10.1115/1.4029017 History: Received November 22, 2013; Revised August 05, 2014; Online January 29, 2015

Modern biomedical computer simulations produce spatiotemporal results that are often viewed at a single point in time on standard 2D displays. An immersive visualization environment (IVE) with 3D stereoscopic capability can mitigate some shortcomings of 2D displays via improved depth cues and active movement to further appreciate the spatial localization of imaging data with temporal computational fluid dynamics (CFD) results. We present a semi-automatic workflow for the import, processing, rendering, and stereoscopic visualization of high resolution, patient-specific imaging data, and CFD results in an IVE. Versatility of the workflow is highlighted with current clinical sequelae known to be influenced by adverse hemodynamics to illustrate potential clinical utility.

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Figures

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Fig. 1

Flowchart describing the immersive visualization workflow. Steps a–f are common to many vascular CFD studies, while steps g through m are the focus of the current work and present new methods applied beyond conventional CFD processing. Medical imaging data is obtained and segmented (a) to create a 3D model (b) of the vasculature. In some cases, a stent is virtually implanted (c) prior to creating the finite-element model (d). Boundary conditions are then applied (e) before conducting a CFD simulation (f). The postprocessing stage begins by resampling the 3D model and hemodynamic results (g), the data is then transformed to meet the scale of the IVE (h) and custom 3D content is generated from the simulation results (j). The data is then prepared for the IVE (k) and the medical images are registered with the 3D model (i) prior to presentation in the IVE (m).

Grahic Jump Location
Fig. 2

A male user of average height is shown standing within the four-walled IVE of the current investigation (a). The LCCA CFD results have been rendered within the IVE and the user is wearing active shutter glasses to allow him to view the results of the workflow in stereoscopic 3D. Blood velocity is communicated by the length and color of the velocity vectors that are pointing into the plane of the screen. A pressure versus time curve plotted with a temporal indicator to communicate position within the cardiac cycle can also be toggled on in the upper left corner of the front screen. A spatial indicator of location within the artery can similarly be toggled on. A schematic illustration of the IVE is shown in (b). The black dots in the image represent high-resolution projectors. The front and side screens are rear-projected, while the floor is top-projected. A schematic illustration of the system components is also provided in (c).

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Fig. 3

3D rendering of spatial image orientation for cases 1 and 2. Slices A–E have been segmented to differentiate the plaque morphology according to the legend on the bottom left. In each slice the inner-most layer (the lumen) is used to create the vessel model. The MR acquisition sequence collects axial images. The eye icon indicates the user's position in virtual space, which controls the opacity of slices in close proximity. OCT images (F–L) are acquired in such a way that images are not necessarily orthogonal to the vessel's central axis. The outline of the stent and lumen are well resolved as seen in the turquoise and white traces, respectively. The thrombus seen in slice J is well resolved with OCT. TAWSS is colocated with the respective medical imaging modalities for both cases. At lower left the user can appreciate the colocation of the region of low TAWSS with increased wall thickness (slice C). At lower right, OCT images elucidate the relationship between stent location and regions of altered TAWSS (slice K). The image on the bottom of the figure shows a user viewing LCCA imaging data, spatially colocalized TAWSS results, and peak systolic velocity vectors within the IVE used for the current investigation. Note the differences in scale between TAWSS in the LCCA results shown in the top (0–30 dyn/cm2) and bottom (0–15 dyn/cm2) images.

Grahic Jump Location
Fig. 4

Temporal and time-averaged hemodynamic quantities rendered in IVE. a–c show velocity vectors at specific temporal locations as indicated on the corresponding pressure waveform. The velocity is communicated by the vector magnitude and color; after reaching maximum velocity immediately prior to peak systole, the velocity decreases with time. The collection of velocity results are used to create TAWSS results as visualized in (d) and (e). The inset of velocity images (c) also shows a region of flow reversal which is consistent with the high values of OSI (f). The image on the bottom of the figure shows a user viewing LCCA velocity vectors within the IVE used for the current investigation. The velocity vectors correspond to the time denoted by time point B (b) above, and the user has navigated into the vessel so that TAWSS on the back (e) of the LCCA is being viewed simultaneously.

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Fig. 5

Predetermined vantage points facilitating smooth navigation during collaboration for the LCCA case. (a) shows the entire section from a wide vantage point. (b) shows the vantage point viewing into the vessel in the direction of blood flow proximal to the carotid bifurcation. (c) shows a vantage within the vessel upstream of the flow divider. (d) is an external view of the LCCA that is optimized for viewing the MR imaging slices. (e) and (f) show the vessel distal to the bifurcation, in each respective daughter branch.

Grahic Jump Location
Fig. 6

IVE images showing CFD data at two time points- immediately following the stent implantation (left) and at 6-month follow-up (right). OCT was used to acquire all slices. A single OCT slice at corresponding locations is shown along with its relationship to TAWSS. A region of thrombus with high TAWSS after stenting (left) that subsequently remodels or migrates to yield a region of relatively diminished TAWSS (right) at 6-month follow-up is also shown. The images on the bottom of the figure show a user viewing OCT images and corresponding TAWSS results from the spatial location of interest where thrombus was observed after stenting. The poststenting immersive results are shown above the follow-up results.

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