Examination of carotid pre-
bifurcation expansion to predict
boundary layer separation
Team 3
Ashley, John, Minh, Jeff, Aa...
Problem Statement
• The purpose of this study is to develop a new
procedure or index for predicting coronary
artery diseas...
Background
• Carotid has been subjected to extensive studies to
try to find factors that can predict atherosclerosis
• Ath...
Background
• Most predictors don’t take into
account fluid mechanical effects which
can lead to low wall shear stress (WSS...
Background
Background
• Relating this pre-bifurcation expansion to a diffuser, we
recognize:
• The change in pressure and
• Bifurcati...
Hypothesis
• Increased atherosclerotic risk corresponds
to pressure changes and large bifurcation
angles in the pre-bifurc...
Procedure
• Region of Interest:
Procedure: Developing an
Index• Using MRI images from literature
with pre-assigned risk levels created
an index that asses...
Procedure: Applying the Index
• Test the system on 6 subjects
• Four measurements taken using ultrasound
• D1 – Diameter a...
Procedure: Applying the
Index
Procedure: Repeatability
• Testing repeatability:
• 4 measurements on one artery
• 5 different “technicians”
Results
Discussion
• Creating the Index
• For the geometries from literature, no velocity measurements
were known, so pressure cha...
Statistics: Repeatability
Technician D1 D2 L V1 Theta ΔP
1 0.556 1.223 0.98 71.2 0.597595 2426.45
2 0.575 0.965 1.06 72.4 ...
Conclusion
• Boundary layer separation can be mathematically related to
pressure difference and bifurcation angle.
• Our p...
Limitations
• 2D geometry capability
• Probe depth
• Grainy image of ultrasound
• Young age group
• Bernoulli’s assumption...
Future Work
• 3D CFD fluid flow
• 3D scanned
geometry from
patients
Lifetime monitoring
• Development of
atherosclerosis o...
References• [1] P. B. Bijari, B. A. Wasserman, and D. A. Steinman, “Carotid Bifurcation Geometry Is an Independent Predict...
Questions?
Upcoming SlideShare
Loading in …5
×

Examination of carotid pre-bifurcation expansion to predict boundary layer separation

542 views

Published on

0 Comments
0 Likes
Statistics
Notes
  • Be the first to comment

  • Be the first to like this

No Downloads
Views
Total views
542
On SlideShare
0
From Embeds
0
Number of Embeds
1
Actions
Shares
0
Downloads
11
Comments
0
Likes
0
Embeds 0
No embeds

No notes for slide

Examination of carotid pre-bifurcation expansion to predict boundary layer separation

  1. 1. Examination of carotid pre- bifurcation expansion to predict boundary layer separation Team 3 Ashley, John, Minh, Jeff, Aaron
  2. 2. Problem Statement • The purpose of this study is to develop a new procedure or index for predicting coronary artery disease in patients by using fluid mechanics and bimolecular principals along with ultrasound imaging techniques.
  3. 3. Background • Carotid has been subjected to extensive studies to try to find factors that can predict atherosclerosis • Atherosclerotic risk is currently determined using Carotid Intima Media Thickness (CIMT) • Measurement of arterial wall thickness, thicker=higher risk • This and most other correlations fail to include measurements which can predict boundary layer separation
  4. 4. Background • Most predictors don’t take into account fluid mechanical effects which can lead to low wall shear stress (WSS) and wall thickening causing plaque buildup • Geometry from beginning of expansion to the bifurcation point is most likely to initiate boundary layer separation Figure 1. The black rectangle encompasses the region of interest for this diffuser model.
  5. 5. Background
  6. 6. Background • Relating this pre-bifurcation expansion to a diffuser, we recognize: • The change in pressure and • Bifurcation angle can lead to boundary layer separation • Boundary layer separation corresponds to low wall shear stress • Areas of low wall shear stress have been shown to correlate to the buildup of atherosclerotic plaque.
  7. 7. Hypothesis • Increased atherosclerotic risk corresponds to pressure changes and large bifurcation angles in the pre-bifurcation expansion.
  8. 8. Procedure • Region of Interest:
  9. 9. Procedure: Developing an Index• Using MRI images from literature with pre-assigned risk levels created an index that assessed risk based on: • Pressure Change • Bifurcation angle [1]
  10. 10. Procedure: Applying the Index • Test the system on 6 subjects • Four measurements taken using ultrasound • D1 – Diameter at beginning of expansion • D2 – Diameter at widest point in bifurcation • L – Length between diameters • Velocity of the blood in the carotid at D1 • Calculate pressure change and bifurcation angle
  11. 11. Procedure: Applying the Index
  12. 12. Procedure: Repeatability • Testing repeatability: • 4 measurements on one artery • 5 different “technicians”
  13. 13. Results
  14. 14. Discussion • Creating the Index • For the geometries from literature, no velocity measurements were known, so pressure change for all risk levels were calculated with the same velocity • So little trend is visible with respect to the pressure change • In reality, these velocities would be different • The accuracy of the index requires a longer term study • Our patients were young and healthy, and since our index is truly predictive, we would need to retest the same patients later in life to see if the predictions were correct.
  15. 15. Statistics: Repeatability Technician D1 D2 L V1 Theta ΔP 1 0.556 1.223 0.98 71.2 0.597595 2426.45 2 0.575 0.965 1.06 72.4 0.352553 2290.50 3 0.533 1.180 1.27 71.1 0.471178 2422.39 4 0.540 1.120 1.18 72.0 0.456845 2451.93 Data taken from same patient by multiple technicians
  16. 16. Conclusion • Boundary layer separation can be mathematically related to pressure difference and bifurcation angle. • Our proposed index cannot be confirmed without long-term studies • The relation between pressure difference and risk requires more data to accurately determine • Trends evident in sample data warrant further investigation
  17. 17. Limitations • 2D geometry capability • Probe depth • Grainy image of ultrasound • Young age group • Bernoulli’s assumptions • Multiple “technician” error
  18. 18. Future Work • 3D CFD fluid flow • 3D scanned geometry from patients Lifetime monitoring • Development of atherosclerosis over time [8]
  19. 19. References• [1] P. B. Bijari, B. A. Wasserman, and D. A. Steinman, “Carotid Bifurcation Geometry Is an Independent Predictor of Early Wall Thickening at the Carotid Bulb,” Stroke, vol. 45, no. 2, pp. 473-478, Feb, 2014. • [2] P. Bokov, P. Flaud, A. Bensalah et al., “Implementing Boundary Conditions in Simulations of Arterial Flows,” Journal of  Biomechanical Engineering-Transactions of the Asme, vol. 135, no. 11, pp. 9, Nov, 2013. • [3] I. B. Casella, "A Practical protocol to measure common carotid artery intima-media thickness," 515-520, C. Presti, ed., Clinics, 2008. • [4] J.-J. Chen, "Skin-scanning technique for superficial blood flow imaging using a high-frequency ultrasound system," C.-H. Cheng, ed., Ultrasonics, 2014, pp. 241-246. • [5] J. Chen, "Numerical investigation of the non-Newtonian pulsatile blood flow in a bifurcation model with a non-planar branch," X.-Y. Lu, ed., Journal of Biomechanics, 2005, pp. 818-832. • [6] T. Ding, "Ultrasound line-by-line scanning method of spatial-temporal active cavitation mapping for high-intensity focused ultrasound," S. Zhang, ed., Ultrasonics, 2014. • [7] Y. Fan, "Numerical Simulation of Pulsatile non-Newtonian flow in the carotid artery bifurcation," W. Jiang, ed., The Chinese Society of Theoretical and Applied Mechanics, 2009, pp. 249-255. • [8] A. Harloff, S. Berg, A. J. Barker et al., “Wall shear stress distribution at the carotid bifurcation: influence of eversion carotid endarterectomy,” European Radiology, vol. 23, no. 12, pp. 3361-3369, Dec, 2013. • [9] H. Karimpour, and E. Javdan, “SIMULATION OF STENOSIS GROWTH IN THE CAROTID ARTERY BY LATTICE BOLTZMANN METHOD,” Journal of Mechanics in Medicine and Biology, vol. 14, no. 2, pp. 20, Apr, 2014. • [10] N. Katakami, H. Kaneto, and I. Shimomura, “Carotid ultrasonography: A potent tool for better clinical practice in diagnosis of atherosclerosis in diabetic patients,” Journal of Diabetes Investigation,vol. 5, no. 1, pp. 3-13, Jan, 2014. • [11] K. H. Nam, T. H. Bok, C. Jin et al., “Asymmetric radial expansion and contraction of rat carotid artery observed using a high-resolution ultrasound imaging system,” Ultrasonics, vol. 54, no. 1, pp. 233-240, Jan, 2014. • [12] R. M. Nerem, “VASCULAR FLUID-MECHANICS, THE ARTERIAL-WALL, AND ATHEROSCLEROSIS,” Journal of  Biomechanical Engineering-Transactions of the Asme, vol. 114, no. 3, pp. 274-282, Aug, 1992. • [13] A. Olsson, "Numerical and experimental studies of flat-walled diffuser elements for valve-less micropumps," G. Stemme, ed., Elsevier Science, 2000, pp. 165-175. • [14] J. F. Polak, "Carotid-Wall Intima-Media Thickness and cardiovascular events," M. J. Pencina, ed., The New England Journal of Medicine, 2011, pp. 213-221. • [15] U. G. R. Schulz, "Major Variation in Carotid Bifurcation Anatomy," A Possible Risk Factor for Plaque Development?, P. M. Rothwell, ed., Stroke, 2001, pp. 2522-2529. • [16] R. K. Singh, "Measurement of Instantaneous Flow Reversals and Velocity Field in a Conical Diffuser," R. S. Azad, ed., Elsevier Science, 1995, pp. 397-419. • [17] F. M. White, "Fluid Mechanics," Mcgraw Hill, 2011. • [18] D. M. Wootton, and D. N. Ku, “Fluid mechanics of vascular systems, diseases, and thrombosis,” Annual Review of  Biomedical Engineering, vol. 1, pp. 299-329, 1999. • [19] M. M. Zarandi, "Effects of bifurcation angle on the wall shear stress in stenosed coronary artery bifurcation," R. Mongrain, ed.
  20. 20. Questions?

×