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: SAE: 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 As there was no surface stress on the top and bottom boundaries of the phantoms, the anti-symmetric circular lamb wave mode was triggered. LFE: Here c1 is the compressional wave (P-wave) velocity and c2 is the shear wave (S-wave) velocity. J. Bao, "Lamb wave generation and detection with piezoelectric wafer active sensors," University of South Carolina (2003).

Methods: FEM Displacement by OCEFinite element model

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 OCEGroup 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.

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