Transcript Presentation

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!