Quantitative assessment of the biomechanical properties of tissue-

mimicking phantoms by optical coherence elastography via numerical

modelsZhaolong 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 SAE22 (1 ) gE c

32

2

2 (1 )

(0.87 1.12 ) gE c

SWE:

SAE:

g

E

c

Young's modulus

density

Possionratio

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

As there was no surface stress on the top and bottom boundaries of the phantoms, the anti-symmetric circular lamb wave mode was triggered.

2 2 2

2

tanh( ) ( )

tanh( ) 4

h k

h k

22 2

21

kc

2

2 222

kc

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 OCE

Finite 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 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!