Abstract

Laser speckle imaging (LSI) is widely used to study blood flow at high spatiotemporal resolution. Several papers recently pointed out that the commonly used LSI equation involves an approximation that could result in incorrect data analysis. We investigated the impact of such an approximation and introduced a simplified analysis method to improve computation time. Flow phantom studies were performed for validation. Moreover, we demonstrated a novel LSI application by imaging blood flow of rat retinas under normal and physiologic-challenge conditions. Because blood-flow abnormality is implicated in many retinal diseases, LSI could provide valuable physiologic, and potentially diagnostic, information.

© 2007 Optical Society of America

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References

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2007

Z. Wang, S. Hughes, S. Dayasundara, and R. S. Menon, Invest. Ophthalmol. Vis. Sci. 27, 258 (2007).

2006

2005

R. Bandyopadhyay, A. S. Gittings, S. S. Suh, P. K. Dixon, and D. J. Durian, Rev. Sci. Instrum. 76, 093110 (2005).
[CrossRef]

2004

H. Cheng, Q. Luo, Q. Liu, Q. Lu, H. Gong, and S. Zeng, Phys. Med. Biol. 49, 1347 (2004).
[CrossRef] [PubMed]

2003

2002

H. Bolay, U. Reuter, A. K. Dunn, Z. Huang, D. A. Boas, and M. A. Moskowitz, Nat. Med. 8, 136 (2002).
[CrossRef] [PubMed]

2001

A. K. Dunn, H. Bolay, M. A. Moskowitz, and D. A. Boas, J. Cereb. Blood Flow Metab. 21, 195 (2001).
[CrossRef] [PubMed]

1994

A. C. Clermont, M. Brittis, T. Shiba, T. Mcgovern, G. L. King, and S. E. Bursell, Invest. Ophthalmol. Visual Sci. 35, 981 (1994).

C. E. Riva, S. D. Cranstoun, R. M. Mann, and G. E. Barnes, Invest. Ophthalmol. Visual Sci. 35, 608 (1994).

1989

U. Dirnagl, B. Kaplan, M. Jacewicz, and W. Pulsinelli, J. Cereb. Blood Flow Metab. 9, 589 (1989).
[CrossRef] [PubMed]

1981

A. F. Fercher and J. D. Briers, Opt. Commun. 37, 326 (1981).
[CrossRef]

R. Bonner and R. Nossal, Appl. Opt. 20, 2097 (1981).
[CrossRef] [PubMed]

1965

J. W. Goodman, Proc. IEEE 53, 1688 (1965).
[CrossRef]

Appl. Opt.

Invest. Ophthalmol. Vis. Sci.

Z. Wang, S. Hughes, S. Dayasundara, and R. S. Menon, Invest. Ophthalmol. Vis. Sci. 27, 258 (2007).

Invest. Ophthalmol. Visual Sci.

A. C. Clermont, M. Brittis, T. Shiba, T. Mcgovern, G. L. King, and S. E. Bursell, Invest. Ophthalmol. Visual Sci. 35, 981 (1994).

C. E. Riva, S. D. Cranstoun, R. M. Mann, and G. E. Barnes, Invest. Ophthalmol. Visual Sci. 35, 608 (1994).

J. Cereb. Blood Flow Metab.

U. Dirnagl, B. Kaplan, M. Jacewicz, and W. Pulsinelli, J. Cereb. Blood Flow Metab. 9, 589 (1989).
[CrossRef] [PubMed]

A. K. Dunn, H. Bolay, M. A. Moskowitz, and D. A. Boas, J. Cereb. Blood Flow Metab. 21, 195 (2001).
[CrossRef] [PubMed]

Nat. Med.

H. Bolay, U. Reuter, A. K. Dunn, Z. Huang, D. A. Boas, and M. A. Moskowitz, Nat. Med. 8, 136 (2002).
[CrossRef] [PubMed]

Opt. Commun.

A. F. Fercher and J. D. Briers, Opt. Commun. 37, 326 (1981).
[CrossRef]

Opt. Lett.

Phys. Med. Biol.

H. Cheng, Q. Luo, Q. Liu, Q. Lu, H. Gong, and S. Zeng, Phys. Med. Biol. 49, 1347 (2004).
[CrossRef] [PubMed]

Proc. IEEE

J. W. Goodman, Proc. IEEE 53, 1688 (1965).
[CrossRef]

Rev. Sci. Instrum.

R. Bandyopadhyay, A. S. Gittings, S. S. Suh, P. K. Dixon, and D. J. Durian, Rev. Sci. Instrum. 76, 093110 (2005).
[CrossRef]

Other

J. W. Goodman, Statistical Optics (Wiley, 1985).

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Figures (3)

Fig. 1
Fig. 1

1 K 2 versus T τ c . 1 K 2 versus flow velocity index of Method I [Eq. (1b)] is depicted by the thinner solid curve and that of Method II [Eq. (2c)] by the thicker solid curve. Their corresponding asymptotes [Eqs. (3, 4)] are shown as dotted lines. Note that it is not apparent that the slope of Eq. (3) is twice that of Eq. (4) because log scales are plotted.

Fig. 2
Fig. 2

Normalized value of K 0 2 K 2 versus mean velocity V at different camera exposure times T obtained from flow phantoms. Normalization was performed with respect to the speckle contrast at the lowest velocity index ( K 0 ) for each exposure time such that all data with different T can be plotted on the same scale. Standard-deviation error bars are shown for the LSI data obtained with T = 10 ms ; error bars for other exposure times of similar magnitudes are omitted for clarity.

Fig. 3
Fig. 3

LSI blood-flow index and percent-change maps of a rat retina. LSI was performed while the animal was breathing air or oxygen. Percent-change maps are the differences between oxygen and air breathing. LSI maps were obtained using A, Newtonian iterative analysis of Method I without the factor ( 1 τ T ) , Eq. (1b); B, Newtonian iterative analysis of Method II with the factor ( 1 τ T ) , Eq. (2c); and C, simplified analysis of Method II with the factor ( 1 τ T ) , Eq. (4). The LSI exposure time was 10 ms . Darker intensities correspond to higher blood flow. The two bright dots on the images are reflections off the corneal surface and/or lens.

Equations (10)

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K = σ s I = 0 T g ( τ ) 2 d τ T ( Method I ) ,
K = σ s I = [ ( τ c 2 T ) { 1 exp ( 2 T τ c ) } ] 1 2 ( Method I ) ,
K = σ s I = 1 T Λ ( τ T ) g ( τ ) 2 d τ ( Method II ) ,
Λ ( τ T ) = { 1 τ T τ T 1 0 otherwise
K = σ s I = 0 T 2 ( 1 τ T ) g ( τ ) 2 d τ T ( Method II ) .
K = σ s I = [ τ c T + 1 2 ( τ c T ) 2 { exp ( 2 T τ c ) 1 } ] 1 2 ( Method II ) .
y = 2 x 1 exp ( 2 x ) , and
when x , y = 2 x or 1 K 2 = 2 T τ c ( Method I )
y = x 1 [ 1 exp ( 2 x ) ] 2 x , and
when x , y = x or 1 K 2 = T τ ( Method II ) .

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