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Research Papers

Characterization of the Discrepancies Between Four-Dimensional Phase-Contrast Magnetic Resonance Imaging and In-Silico Simulations of Cerebrospinal Fluid Dynamics

[+] Author and Article Information
Soroush Heidari Pahlavian

Conquer Chiari Research Center,
Department of Mechanical Engineering,
The University of Akron,
Akron, OH 44325
e-mail: sh113@uakron.edu

Alexander C. Bunck

Department of Radiology,
University Hospital of Cologne,
Cologne 50923, Germany
e-mail: alexander.bunck@uk-koeln.de

Francis Loth

Conquer Chiari Research Center,
Department of Mechanical Engineering,
The University of Akron,
Akron, OH 44325
e-mail: loth@uakron.edu

R. Shane Tubbs

Children’s of Alabama,
Birmingham AL 35233
Department of Anatomical Sciences,
St. George’s University,
St. George, Grenada
Centre for Anatomy and Human Identification,
Dundee University,
Dundee DD1 4HN, UK
e-mail: Shane.Tubbs@childrensal.org

Theresia Yiallourou

Laboratory of Hemodynamics and Cardiovascular Technology,
EPFL,
Lausanne 1015, Switzerland
e-mail: thiresia.giallourou@epfl.ch

Jan Robert Kroeger

Department of Radiology,
University Hospital of Cologne,
Cologne 50923, Germany
e-mail: janrobertkroeger@gmail.com

Walter Heindel

Department of Clinical Radiology,
University Hospital of Muenster,
Muenster 48149, Germany
e-mail: heindel@uni-muenster.de

Bryn A. Martin

Conquer Chiari Research Center,
Department of Mechanical Engineering,
The University of Akron,
Akron, OH 44325
e-mail: director@chiari-research.org

Manuscript received August 18, 2014; final manuscript received January 21, 2015; published online February 20, 2015. Assoc. Editor: Tim David.

J Biomech Eng 137(5), 051002 (May 01, 2015) (8 pages) Paper No: BIO-14-1406; doi: 10.1115/1.4029699 History: Received August 18, 2014; Revised January 21, 2015; Online February 20, 2015

The purpose of the present study was to compare subject-specific magnetic resonance imaging (MRI)-based computational fluid dynamics (CFD) simulations with time-resolved three-directional (3D) velocity-encoded phase-contrast MRI (4D PCMRI) measurements of the cerebrospinal fluid (CSF) velocity field in the cervical spinal subarachnoid space (SSS). Three-dimensional models of the cervical SSS were constructed based on MRI image segmentation and anatomical measurements for a healthy subject and patient with Chiari I malformation. CFD was used to simulate the CSF motion and compared to the 4D PCMRI measurements. Four-dimensional PCMRI measurements had much greater CSF velocities compared to CFD simulations (1.4 to 5.6× greater). Four-dimensional PCMRI and CFD both showed anterior and anterolateral dominance of CSF velocities, although this flow feature was more pronounced in 4D PCMRI measurements compared to CFD. CSF flow jets were present near the nerve rootlets and denticulate ligaments (NRDL) in the CFD simulation. Flow jets were visible in the 4D PCMRI measurements, although they were not clearly attributable to nerve rootlets. Inclusion of spinal cord NRDL in the cervical SSS does not fully explain the differences between velocities obtained from 4D PCMRI measurements and CFD simulations.

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Figures

Grahic Jump Location
Fig. 2

In vivo CSF flow waveforms measured by 4D PCMRI for the healthy subject (top) and CMI patient (bottom) along the spine from C1 to the 1st thoracic vertebrae (th). Note, the magnitude of CSF flow amplitude changes along the cervical spine; a change likely due to SSS compliance. For the present study, the waveform with the greatest amplitude was used as the CFD flow boundary condition. This waveform was located at C3 for the healthy volunteer and at C2M for the CMI patient (C2P = C2 spinous process, C2M = middle of C2 vertebrae).

Grahic Jump Location
Fig. 1

Modeling process for the cervical SSS in the healthy case. (a) MR image segmentation to reconstruct the SSS. (b) Addition of idealized NRDL. (c) CSF flow simulation using CFD.

Grahic Jump Location
Fig. 3

Comparison of peak systolic (negative values) and peak diastolic (positive values) CSF velocities along the cervical spine between 4D PCMRI and CFD for the healthy volunteer (top) and CMI patient (bottom). Peak systolic and peak diastolic velocities were defined as the maximum magnitude of through-plane velocities that occurred anywhere within the designated cross sections at the time points corresponding to peak systole and peak diastole, respectively.

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Fig. 4

Distribution of through-plane peak systolic velocity magnitude at different locations along the cervical spine plotted (a) for the healthy case and (b) for the CMI patient. In each set of contours, the left and right column represents the results obtained from the CFD simulation and 4D PCMRI measurements, respectively. Note: CFD results are shown in two columns; one with a velocity range identical to 4D PCMRI and another with a smaller velocity range to show detail in the CFD velocity profiles.

Grahic Jump Location
Fig. 5

Distribution of midsagittal peak systolic velocity magnitude for the healthy subject obtained from CFD (left) and 4D PCMRI (right). Note that the magnitude images used to obtain the CFD geometry (left) had higher resolution than those obtained by 4D PCMRI (right).

Grahic Jump Location
Fig. 6

Formation of concentrated velocity regions (jets) between nerve rootlets (NR) and denticulate ligaments (DL). The anterior and posterior side of the geometry is represented by “A” and “P,” respectively. Note that due to the variable insertion lines of the idealized DLs into the spinal cord, these structures were not completely extended inferiorly between the rootlets at some levels, such as the depicted level.

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