Abstract

Optical coherence tomography (OCT) has been applied to the study of the microscopic deformation of biological tissue under compressive stress. We describe the hardware and theory of operation of an OCT elastography system that measures internal displacements as small as a few micrometers by using 2D cross-correlation speckle tracking. Results obtained from gelatin scattering models, pork meat, and intact skin suggest possible medical applications of the technique.

© Optical Society of America

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References

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  1. K. J. Parker, L. Gao, R. M. Lerner, and S. F. Levinson, "Techniques for elastic imaging: A review," IEEE Eng. Med. Biol. Mag 15, 52-59 (1996).
    [CrossRef]
  2. J. Ophir, I. Cespedes, H. Ponnekanti, Y. Yazdi, and X. Li, "Elastography: a quantitative method for imaging the elasticity of biological tissues," Ultras. Imaging 13, 111-134 (1991).
    [CrossRef]
  3. A. P. Sarvazyan, A. R. Skovoroda, S. Y. Emelianov, J. B. Fowlkes, J. G. Pipe, R. S. Adler, R. B. Buxton, and P. L. Carson, "Biophysical bases of elasticity imaging," Acoust. Imaging 21, 223-240 (1995).
    [CrossRef]
  4. Y. Yamakoshi, J. Sato, and T. Sato, "Ultrasonic imaging of internal vibration of soft tissue under forced vibration," IEEE Trans. Ultras., Ferro., Freq. Control 37, 223-240 (1990).
  5. D. Huang, E. A. Swanson, C. P. Lin, J. S. Schuman, W. G. Stinson, W. Chang, M. R. Hee, T. Flotte, K. Gregory, C. A. Puliafito, and J. G. Fujimoto, "Optical coherence tomography," Science 254, 1178-1181 (1991).
    [CrossRef] [PubMed]
  6. A. F. Fercher, C. K. Hitzenberger, W. Drexler, G. Kamp, and H. Sattmann, "In vivo optical coherence tomography," Am. J. Ophthalmol. 116, 113-114 (1993).
    [PubMed]
  7. J. A. Izatt, M. Kulkarni, K. Kobayashi, M. V. Sivak, J. K. Barton, and A. J. Welsh, "Optical coherence tomography for biodiagnostics," Optics and Photonics News 8, 41-47 (1997).
    [CrossRef]
  8. B. Bouma, G. J. Tearney, S.A. Boppart, M. R. Hee, M. E. Brezinski, and J. G. Fujimoto, "High resolution optical coherence tomographic imaging using a mode-locked Ti:Al2O3 laser source," Opt. Lett. 20, 1486-1488 (1995).
    [CrossRef] [PubMed]
  9. J. A. Smith, R. Muthupillai, P. J. Rossman, T. C. Hulshizer, J. F. Greenleaf, and R. L. Ehman, "Characterization of biomaterials using magnetic resonance elastography," Rev. Progr. Quantitat. NonDestr. Eval. 2, 1323-1330 (1997).
  10. J. M. Schmitt and A. Kn" uttel, "Model of optical coherence tomography of heterogenous tissue," J. Opt. Soc. Am. A 14, 1231-1242 (1997).
    [CrossRef]
  11. T. Varghese, M. Bilgen, and J. Ophir "Multiresolution imaging in elastography," IEEE Trans. Ultras. Ferro. Freq. Control 45, 65-75 (1998).
    [CrossRef]
  12. J. M. Schmitt, S. L. Lee, and K. M. Yung, "An optical coherence microscope with enhanced resolving power," Opt. Commun. 142, 203-207 (1997).
    [CrossRef]
  13. R. E. Boucher and J. C. Hassab,"Analysis of discrete implementation of generalized cross correlator," IEEE Trans. Acoust. Speech, Signal Proc. 29, 609-611 (1981).
    [CrossRef]

Other (13)

K. J. Parker, L. Gao, R. M. Lerner, and S. F. Levinson, "Techniques for elastic imaging: A review," IEEE Eng. Med. Biol. Mag 15, 52-59 (1996).
[CrossRef]

J. Ophir, I. Cespedes, H. Ponnekanti, Y. Yazdi, and X. Li, "Elastography: a quantitative method for imaging the elasticity of biological tissues," Ultras. Imaging 13, 111-134 (1991).
[CrossRef]

A. P. Sarvazyan, A. R. Skovoroda, S. Y. Emelianov, J. B. Fowlkes, J. G. Pipe, R. S. Adler, R. B. Buxton, and P. L. Carson, "Biophysical bases of elasticity imaging," Acoust. Imaging 21, 223-240 (1995).
[CrossRef]

Y. Yamakoshi, J. Sato, and T. Sato, "Ultrasonic imaging of internal vibration of soft tissue under forced vibration," IEEE Trans. Ultras., Ferro., Freq. Control 37, 223-240 (1990).

D. Huang, E. A. Swanson, C. P. Lin, J. S. Schuman, W. G. Stinson, W. Chang, M. R. Hee, T. Flotte, K. Gregory, C. A. Puliafito, and J. G. Fujimoto, "Optical coherence tomography," Science 254, 1178-1181 (1991).
[CrossRef] [PubMed]

A. F. Fercher, C. K. Hitzenberger, W. Drexler, G. Kamp, and H. Sattmann, "In vivo optical coherence tomography," Am. J. Ophthalmol. 116, 113-114 (1993).
[PubMed]

J. A. Izatt, M. Kulkarni, K. Kobayashi, M. V. Sivak, J. K. Barton, and A. J. Welsh, "Optical coherence tomography for biodiagnostics," Optics and Photonics News 8, 41-47 (1997).
[CrossRef]

B. Bouma, G. J. Tearney, S.A. Boppart, M. R. Hee, M. E. Brezinski, and J. G. Fujimoto, "High resolution optical coherence tomographic imaging using a mode-locked Ti:Al2O3 laser source," Opt. Lett. 20, 1486-1488 (1995).
[CrossRef] [PubMed]

J. A. Smith, R. Muthupillai, P. J. Rossman, T. C. Hulshizer, J. F. Greenleaf, and R. L. Ehman, "Characterization of biomaterials using magnetic resonance elastography," Rev. Progr. Quantitat. NonDestr. Eval. 2, 1323-1330 (1997).

J. M. Schmitt and A. Kn" uttel, "Model of optical coherence tomography of heterogenous tissue," J. Opt. Soc. Am. A 14, 1231-1242 (1997).
[CrossRef]

T. Varghese, M. Bilgen, and J. Ophir "Multiresolution imaging in elastography," IEEE Trans. Ultras. Ferro. Freq. Control 45, 65-75 (1998).
[CrossRef]

J. M. Schmitt, S. L. Lee, and K. M. Yung, "An optical coherence microscope with enhanced resolving power," Opt. Commun. 142, 203-207 (1997).
[CrossRef]

R. E. Boucher and J. C. Hassab,"Analysis of discrete implementation of generalized cross correlator," IEEE Trans. Acoust. Speech, Signal Proc. 29, 609-611 (1981).
[CrossRef]

Supplementary Material (2)

» Media 1: MOV (783 KB)     
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Figures (10)

Figure 1.
Figure 1.

Setup of experimental elastography system built around a scanning white-light interferometer.

Figure 2.
Figure 2.

Image processing steps used to obtain quantitative estimates of local displacement and strain.

Figure 3.
Figure 3.

10-frame movie showing a sequence of OCT images taken during stepwise compression of a gelatin phantom (5 μm displacement of the top surface per step) The dimensions of the images are 1 mm (width) × 1 mm (depth) and the intensities are mapped onto a logarithmic gray scale. [Media 1]

Figure 4.
Figure 4.

Internal structure of the gelatin scattering model from which the sequence of images in Fig. 3 were obtained.

Figure 5.
Figure 5.

Displacement vector field d→(r, z) measured for the gelatin model sequence over the first 5 frames. The bar gives the scale of the vector lengths.

Figure 6.
Figure 6.

5-frame movie showing a sequence of OCT images taken during stepwise compression of pork meat (10 μm displacement of the top surface per step) The dimensions of the images are 1.2 mm (width)× 0.7 mm (depth) and the intensities are mapped onto a logarithmic gray scale. [Media 2]

Figure 7.
Figure 7.

Internal composition of the pork meat sample, showing the location of the muscle and fat layers.

Figure 8.
Figure 8.

(a) Image of the axial displacements inside the pork meat sample, calculated by cross correlation analysis over the 5-frame sequence. The black areas outlined with dotted lines indicate where the signal-to-noise ratio was too low for calculation of the displacements, (b) Strains estimation for the areas marked ‘1’ and ‘2’ in in the displacement image on the left.

Figure 9.
Figure 9.

(a) Unprocessed OCT image of the skin of the finger, acquired in vivo with compression applied during every other A-line. (b) Image reconstructed by realigning displaced pixels, (c) and (d) Enlarged regions of upper images. The dimensions of the upper images are 1.2 mm (width)× 0.7 mm (depth). The intensities are mapped onto a logarithmic gray scale.

Figure 10.
Figure 10.

Images of (a) lateral and (b) axial displacement of the skin.

Equations (16)

Equations on this page are rendered with MathJax. Learn more.

I r z = exp ( 2 μ ¯ s z ) σ b r z h r r τ τ r dr
= exp ( 2 μ ¯ s z ) [ σ b r z * * h r τ ]
h r τ = Γ ( τ ) p ( r )
Γ ( τ ) = Re [ E s ( t ) E s * ( t + τ ) ]
= exp ( τ 2 τ c 2 ) cos ( 2 k 0 )
p ( r ) = exp [ r 2 ( 4 f 2 k 0 2 D 2 ) ]
I 1 r z = [ δ r z σ b * * h r τ ] exp ( 2 μ ¯ s z )
= h 0,0 σ b exp ( 2 μ ¯ s z )
I 2 r z = [ δ r + r d z + z d σ b * * h r τ ] exp ( 2 μ ¯ s z )
= h r d 2 n z d c σ b exp ( 2 μ ¯ s z )
ρ r z = Z 2 Z 2 R 2 R 2 I 1 r z I 2 ( r r , z z ) drdz Z 2 Z 2 R 2 R 2 I 1 2 r z drdz Z 2 Z 2 R 2 R 2 I 2 2 r r z z drdz
r ̂ d = max { ρ r z } for z = 0 , R 2 r R 2 .
z ̂ d = max { ρ r z } for r = 0 , Z 2 z Z 2
s r z = lim Δ r , Δ z 0 d r z d ( r + Δ r , z + Δ z ) ( Δ r ) 2 + ( Δ z ) 2
s ̂ z r z Δ d z Δ z = d ̂ z r z d ̂ z ( r , z + Δ z ) Δ z
ρ i j = i = M 2 M 2 j = N 2 N 2 I 1 i 0 j 0 I 2 i 0 i j 0 j i = M 2 M 2 j = N 2 N 2 I 1 2 r z i = M 2 M 2 j = N 2 N 2 I 2 2 i 0 i j 0 j

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