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Flow characteristics in a canine aneurysm model: A comparison of 4D accelerated phase-contrast MR measurements and computational fluid dynamics simulations
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10.1118/1.3652917
/content/aapm/journal/medphys/38/11/10.1118/1.3652917
http://aip.metastore.ingenta.com/content/aapm/journal/medphys/38/11/10.1118/1.3652917

Figures

Image of FIG. 1.
FIG. 1.

Segmented and meshed geometries of the two aneurysms from PC-VIPR MRA registered with adjacent soft tissue: (a) Aneurysm A and (b) aneurysm B.

Image of FIG. 2.
FIG. 2.

Comparison of 3D velocity vector fields at diastole [three components Vx, Vy, and Vz and the velocity amplitude V] obtained from subject-specific CFD simulations and PC-VIPR MRA measurements for (a) a transverse plane and (b) a longitudinal plane in aneurysm A. In both plots, CFD1 and CFD2 denote non-Newtonian and Newtonian CFD simulations, respectively. Color bars corresponding to three plots of each column are shown at the end of each column. The unit used for velocity is m/s for all plots in (a) and (b).

Image of FIG. 3.
FIG. 3.

The estimated similarity values [see Eq. (A1)], absolute magnitude and angular differences between three pairs of velocity fields [MRA vs. CFD1, MRA vs. CFD2, and CFD1 vs. CFD2] for (a) the transverse and (b) the longitudinal planes in aneurysm A illustrated in Figs. 2(a) and 2(b), respectively. The velocity data correspond to a phase at the diastole. Arrows on 3D velocity vector plots [top plots of both (a) and (b)] indicate a border region between the velocity jet and the low-velocity recirculation zone. In this figure, CFD1 and CFD2 denote non-Newtonian and Newtonian CFD simulations, respectively. Manually-delineated contours on both (a) and (b) indicate regions within the aneurysm dome. Mag (m/s), Ang (degree) and Sim [0-1] denote the absolute magnitude and angular differences, and the similarity metric between two velocity vectors, respectively. The arrows in the similarity plots (left lower three columns) point to low similarity values, where arrows in the absolute magnitude (right lower three columns) and angular (middle lower three columns) difference plots point to large discrepancies in both magnitude and direction of two sets of comparing vectors.

Image of FIG. 4.
FIG. 4.

Comparison of 3D velocity vector fields at the peak systole (three components Vx, Vy and Vz and the velocity amplitude V) obtained from subject-specific CFD simulations and PC-VIPR MRA measurements for (a) a transverse plane and (b) a longitudinal plane in aneurysm A. In both plots, CFD1 and CFD2 denote non-Newtonian and Newtonian CFD simulations, respectively. Color bars corresponding to three plots of each column are shown at the end of each column. The unit used for velocity is m/s for all plots in (a) and (b). The arrow in (b) points to possible MRA measurement errors.

Image of FIG. 5.
FIG. 5.

The estimated similarity values [see Eq. (A1)], absolute magnitude and angular differences between three pairs of velocity fields [MRA vs. CFD1, MRA vs. CFD2, and CFD1 vs. CFD2] for (a) the transverse and (b) the longitudinal planes in aneurysm A illustrated in Figs. 2(a) and 2(b), respectively. The velocity data correspond to the peak systole. In this figure, CFD1 and CFD2 denote non-Newtonian and Newtonian CFD simulations, respectively. Mag (m/s), Ang (degree) and Sim [0-1] denote the absolute magnitude and angular differences, and the similarity metric between two velocity vectors, respectively. The arrow in the similarity plots (left lower three columns) points to low similarity values, where arrows in the absolute magnitude (right lower three columns) and angular (middle lower three columns) difference plots point to large discrepancies in both magnitude and direction of two sets of comparing vectors.

Image of FIG. 6.
FIG. 6.

Plots of streamlines (i.e., lines of tangent to instantaneous velocity vectors) of CFD simulated and PC-MRA measured velocity vectors at diastole for (a) Aneurysms A and (b) B, respectively. Streamlines were color encoded using velocity amplitude (0–0.8 m/s). In this figure, CFD1 and CFD2 denote non-Newtonian and Newtonian CFD simulations, respectively.

Image of FIG. 7.
FIG. 7.

Side-by-side comparisons for TA-WSS values derived from PC-MRA-estimated and CFD. Arrows points to the likely locations where the inflow jets impinge the walls.

Image of FIG. 8.
FIG. 8.

Selected images of the estimated WSS under noise-free for three different voxel sizes (5, 250 and 750 μm) and their estimated correlation values.

Image of FIG. 9.
FIG. 9.

A plot of the estimated correlation values with respect to different simulated voxel sizes and measurement noise. Ten realizations were used to obtain each data point displayed in this plot.

Image of FIG. 10.
FIG. 10.

Estimated correlation values for simulated velocity data with voxel sizes of 0.525 mm and 0.620 mm that are comparable to MRA-measured velocity data in Aneurysms A and B, respectively. Each data point was obtained by ten realizations and error bars stand for one standard deviation. Two black stars denote two data points for the correlation values corresponding to these TA-WSS estimates shown in Figs. 7(a) and 7(b).

Image of FIG. 11.
FIG. 11.

Illustrations of the calculation of WSS.

Tables

Generic image for table
TABLE I.

Basic geometrical and flow parameters of Aneurysms A and B. The aspect ratio is defined as the ratio between the aneurysm height and the neck width.

Generic image for table
TABLE II.

Estimated absolute magnitude and angular differences, and similarity values with two aneurysm sacs for three pairs of velocity vector fields: MRA versus non-Newtonian CFD simulations (CFD1), MRA versus Newtonian CFD simulations (CFD2) and CFD1 versus CFD2. The mean values (±one standard deviation) were estimated within the manually-segmented aneurysm domes [see Figs. 3(a) and 3(b)].

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/content/aapm/journal/medphys/38/11/10.1118/1.3652917
2011-10-31
2014-04-23
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752b84549af89a08dbdd7fdb8b9568b5 journal.articlezxybnytfddd
Scitation: Flow characteristics in a canine aneurysm model: A comparison of 4D accelerated phase-contrast MR measurements and computational fluid dynamics simulations
http://aip.metastore.ingenta.com/content/aapm/journal/medphys/38/11/10.1118/1.3652917
10.1118/1.3652917
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