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Quantitative assessment of the biomechanical properties of tissue-mimicking phantoms by optical coherence elastography via numerical models Zhaolong Han, Jiasong Li, Manmohan Singh, Chen Wu, Chih-hao Liu, Shang Wang, Rita Idugboe, Narendran Sudheendran, Michael D. Twa, and Kirill V. Larin Department of Biomedical Engineering, University of Houston Outline • • • • Introduction Methods Results Conclusion Introduction • Assessing the biomechanical properties of tissues can help in diagnostics of different diseases. • Optical Coherence Elastography (OCE) is an emerging technique allowing noninvasive quantification of tissue biomechanical properties • Quantification methods: shear wave equation (SWE); acoustic surface wave equation (SAE) ; lamb frequency equation (LFE); finite element method (FEM); gold standard: uniaxial compressional test. Methods: OCE setup OCE set up Phantom measurement J. Li, et al, "Dynamic optical coherence tomography measurements of elastic wave propagation in tissue-mimicking phantoms and mouse cornea in vivo," J Biomed Opt 18(12), (2013). Methods: SWE and SAE SWE: E 2 (1 )cg2 SAE: 2 (1 )3 E cg2 2 (0.87 1.12 ) E Young's modulus density Possionratio cg Group wave velocity B. F. Kennedy, et al., "A Review of Optical Coherence Elastography: Fundamentals, Techniques and Prospects," IEEE J Sel Top Quant 20(2), (2014). Methods: LFE LFE: tanh( h) (k 2 2 )2 tanh( h) 4k 2 k 2 2 2 c12 k 2 2 2 c22 Here c1 is the compressional wave (P-wave) velocity and c2 is the shear wave (S-wave) velocity. As there was no surface stress on the top and bottom boundaries of the phantoms, the anti-symmetric circular lamb wave mode was triggered. J. Bao, "Lamb wave generation and detection with piezoelectric wafer active sensors," University of South Carolina (2003). Methods: FEM Finite element model Displacement by OCE Results: LFE vs OCE LFE obtained Young’s modulus The Young’s modulus by LFE are 25kPa for 1%, 55kPa for 1.5% and 160 kPa for 2% agar phantoms. Results: FEM vs OCE Group velocities by OCE Group velocities by FEM By comparing on the group velocities, the Young’s modulus by FEM are 18kPa for 1%, 50kPa for 1.5% and 160 kPa for 2% agar phantoms. Results: Compressional tests Uniaxial compressional test The Young’s modulus is calculated at strain=0.1. Results: All shear wave equation (SWE), surface acoustic wave equation (SAE), lamb-frequency equation (LFE), finite element method (FEM) and uniaxial mechanical compressional testing (mechanical testing) Conclusions • Combining OCE with numerical analysis is a promising method to quantitatively reconstruct elasticity. • LFE and the FEM can extract the Young’s modulus with higher accuracy than other simplified models such as SWE and SAE. • Future work will entail applying this method on tissues for noninvasive assessment of elasticity. Thank you!