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Preliminary Study in characterizing tissue growth through residual strain

Preliminary Study in characterizing tissue growth through residual strain. Eunice Yi July 2009. Introduction. Tissue Engineering Used to restore and maintain tissue/organ function The Application Pediatric Right Ventricular Outflow Tract (RVOT) replacements The Problem

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Preliminary Study in characterizing tissue growth through residual strain

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  1. Preliminary Study in characterizing tissue growth through residual strain Eunice Yi July 2009

  2. Introduction • Tissue Engineering • Used to restore and maintain tissue/organ function • The Application • Pediatric Right Ventricular Outflow Tract (RVOT) replacements • The Problem • Body rejecting tissue, growth limitations • The Need • Thorough study of native tissue behavior • AIM • To characterize the pattern of residual strain in porcine pulmonary trunks (PT)

  3. The Tissue Aorta Bifurcation Region Pulmonary Trunk Sinotubular Junction Right Ventricle

  4. MPA Circumference RPA circumference Ligamentum arteriosum Bifurcation Axial length measurement Sinotubular junction Annulus Tissue Preparation • Two rings cut • Sinotubular junction • Bifurcation • Microdots applied

  5. The Tests • Opening Angle/Stretch: • Images taken before and after tissue is cut • Flexural Test: • 3-point bending • AC and WC Camera Temp control Container with medium Bending Beam TransverseBar Tissue Sample

  6. Taking Images NO LOAD 1st Cut Image Last Image

  7. Calculations • ImageJ used to calculate OA and circumferential lengths • Circumferential Stretch • Residual Strain NO LOAD ZERO STRESS

  8. OA and Circumferential Stretch Results • Sinotubular junction has greater residual strain than Bifurcation region • Correlation between OA and residual strain

  9. Explaining the Results Bifurcation Bifurcation End Sample Sinus Sinus End Sample

  10. Flexural Tests Against Curvature (AC) With Curvature (WC)

  11. Flexure Test Results • Comparing against curvature (AC) and with curvature (WC) stiffness for bifurcation and sinus end samples

  12. Possible Indication • Similar stiffness values may indicate isotropic properties throughout tissue layers Image: http://www.nature.com/nrm/journal/v8/n11/images/nrm2262-f5.jpg

  13. Flexure Test Results • Comparing bifurcation, sinotubular junction, AC, and WC stiffness across all samples

  14. Flexural Test Results • Comparing Bifurcation and Sinus End Effective Stiffness

  15. Conclusion and Future Research • Preliminary data is promising and rough trends may be seen • The significance of these trends is difficult to tell • More samples need to be tested • Expand test to see trend of residual strain over different aged samples • Study residual stress

  16. Acknowledgements • The national BBSI program (http://bbsi.eeicom.com) is a joint initiative of the NIH-NIBIB and NSF-EEC, and the BBSI @ Pitt is supported by the National Science Foundation under Grant EEC-0234002 • Dr. Michael Sacks for this great opportunity • Bahar Fata and Chad Eckert for their guidance and assistance • University of Pittsburgh

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