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1.
FIGURE 4

FIGURE 4. From: Hemodynamic Changes Quantified in Abdominal Aortic Aneurysms with Increasing Exercise Intensity Using MR Exercise Imaging and Image-Based Computational Fluid Dynamics.

Comparison of measured infrarenal (IR) flow waveform (solid line) and simulated IR flow waveform (dashed line) during a single cardiac cycle at rest (black) and mild exercise levels (red) for all 10 subjects.

Ga-Young Suh, et al. Ann Biomed Eng. ;39(8):2186-2202.
2.
FIGURE 5

FIGURE 5. From: Hemodynamic Changes Quantified in Abdominal Aortic Aneurysms with Increasing Exercise Intensity Using MR Exercise Imaging and Image-Based Computational Fluid Dynamics.

Volume rendering visualization of the magnitude of the ensemble average of the velocity field at rest, mild exercise, and moderate exercise levels at peak systole, end-systole, mid-diastole, and end-diastole in the cardiac cycle for subjects 1 and 10.

Ga-Young Suh, et al. Ann Biomed Eng. ;39(8):2186-2202.
3.
FIGURE 3

FIGURE 3. From: Hemodynamic Changes Quantified in Abdominal Aortic Aneurysms with Increasing Exercise Intensity Using MR Exercise Imaging and Image-Based Computational Fluid Dynamics.

Measured volumetric flow rate at supraceliac (SC) and infrarenal (IR) locations at rest and mild exercise levels using a phase-contrast magnetic resonance imaging sequence. The flow rates represent the average of the peak-aligned curves for 10 subjects.

Ga-Young Suh, et al. Ann Biomed Eng. ;39(8):2186-2202.
4.
FIGURE 8

FIGURE 8. From: Hemodynamic Changes Quantified in Abdominal Aortic Aneurysms with Increasing Exercise Intensity Using MR Exercise Imaging and Image-Based Computational Fluid Dynamics.

3D models of 10 subjects with the highlighted aneurysm domain for particle residence time (PRT) computation (left of each pair) and contour plots of PRT at rest, mild exercise, and moderate exercise levels (right of each pair). The contour plots of PRT were colorized based on the seeded positions of the particles. We chose PRT with particles released in mid-diastole.

Ga-Young Suh, et al. Ann Biomed Eng. ;39(8):2186-2202.
5.
FIGURE 6

FIGURE 6. From: Hemodynamic Changes Quantified in Abdominal Aortic Aneurysms with Increasing Exercise Intensity Using MR Exercise Imaging and Image-Based Computational Fluid Dynamics.

Mean wall shear stress (MWSS) and oscillatory shear index (OSI) values at rest (black), mild exercise (gray) and moderate exercise levels (white), averaged over 10 subjects. For each subject, MWSS and OSI values were computed in 1-cm strips at supraceliac (SC), infrerenal (IR), and mid-aneurysm (MA) locations.

Ga-Young Suh, et al. Ann Biomed Eng. ;39(8):2186-2202.
6.
FIGURE 9

FIGURE 9. From: Hemodynamic Changes Quantified in Abdominal Aortic Aneurysms with Increasing Exercise Intensity Using MR Exercise Imaging and Image-Based Computational Fluid Dynamics.

3D models of 10 subjects (left of each pair) and particle residence index (PRI) vs. time (right of each pair) at rest (black), mild exercise (dark gray) and moderate exercise levels (light gray). PRI were calculated at each second by dividing the number of residing particles by the total number of released particles.

Ga-Young Suh, et al. Ann Biomed Eng. ;39(8):2186-2202.
7.
FIGURE 7

FIGURE 7. From: Hemodynamic Changes Quantified in Abdominal Aortic Aneurysms with Increasing Exercise Intensity Using MR Exercise Imaging and Image-Based Computational Fluid Dynamics.

Particle tracing over successive time during rest, mild exercise, and moderate exercise in the aneurysms of subjects 1 and 10. Particles were released at 0 s, and monitored for 10 s. Note that at rest, a number of particles still resided in the lower portion of the aneurysm lobe at 10 s for both subjects. During mild exercise, most of the particles left the aneurysm at 2 and 5 s for subjects 1 and 10, respectively. During moderate exercise, most of the particles left the aneurysm at 1 and 2 s for subjects 1 and 10, respectively.

Ga-Young Suh, et al. Ann Biomed Eng. ;39(8):2186-2202.
8.
FIGURE 2

FIGURE 2. From: Hemodynamic Changes Quantified in Abdominal Aortic Aneurysms with Increasing Exercise Intensity Using MR Exercise Imaging and Image-Based Computational Fluid Dynamics.

A finite element mesh and boundary conditions: the magnified view of the mesh is shown at the aneurysm for subject 10; as an inlet boundary condition, supraceliac (SC) flow waveform was prescribed using a Womersley velocity profile38; For each outlet, a three-element Windkessel (RCR) model was used to represent the downstream impedance. Rp, C, and Rd parameter values represent a proximal resistance (Rp), the resistance of the proximal arteries, capacitance (C), the compliance of the proximal arteries, and distal resistance (Rd), the resistance of the distal vessels including arterioles and capillaries.35 These RCR parameter values for each outlet were initially chosen based on flow splits, total resistance, total compliance, and measured blood pressure; the infrarenal (IR) flow waveform was used as one of the objectives to systematically tune the RCR parameter values of outlets and match the simulated results closely to the measured IR flow waveform and blood pressure.29

Ga-Young Suh, et al. Ann Biomed Eng. ;39(8):2186-2202.
9.
FIGURE 1

FIGURE 1. From: Hemodynamic Changes Quantified in Abdominal Aortic Aneurysms with Increasing Exercise Intensity Using MR Exercise Imaging and Image-Based Computational Fluid Dynamics.

Data acquisition using magnetic resonance imaging (MRI). (a) AAA subjects were scanned in the supine position using a 1.5 T Signa MR scanner (GE Medical Systems, Milwaukee WI). We used a 3D gadolinium-enhanced MRA sequence to image the lumen of the abdominal aorta. Custom software37 was used to process these images, construct a 3D solid model, and generate a finite element mesh based on the model geometry (MeshSim, Simmetrix, Clifton Park, NY). (b) In a separate imaging study, AAA subjects were scanned in the upright position using a 0.5 T Signa MR scanner (GE Medical Systems, Milwaukee, WI). We acquired cine phase-contrast MRI (PC-MRI) data at supraceliac (SC) and infrarenal (IR) locations during rest and performing lower-extremity mild exercise using an MR-compatible exercise cycle. The PC-MRI images were used to calculate the time-dependent volumetric flow rate at SC and IR locations with 24 time points per cardiac cycle. SC and IR flow waveforms at the moderate exercise level were extrapolated from the SC and IR flow waveforms obtained during mild exercise.

Ga-Young Suh, et al. Ann Biomed Eng. ;39(8):2186-2202.

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