Abstract

The relationship between optical properties and image contrast in confocal imaging is investigated. A Monte Carlo simulation has been developed to analyze the effects of changes in scattering, index of refraction, and absorption in a three-layer medium. Contrast was calculated from the computed signal-to-background ratios for changes in tissue optical properties. Results show that the largest source of contrast is changes in refractive index.

© 1996 Optical Society of America

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References

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  1. W. Petroll, H. Cavanagh, J. Jester, “Three-dimensional imaging of corneal cells using in vivo confocal microscopy,” J. Microsc. 170, 213–219 (1993).
    [CrossRef] [PubMed]
  2. M. Rajadhyaksha, M. Grossman, D. Esterwitz, R. Webb, R. Anderson, “In vivo confocal scanning laser microscope of human skin: melanin provides strong contrast,” J. Invest. Dermatol. 104, 946–952 (1995).
    [CrossRef] [PubMed]
  3. J. Schmitt, A. Knuttel, M. Yadlowski, M. Eckhaus, “Optical-coherence tomography of a dense tissue: statistics of attenuation and backscattering,” Phys. Med. Biol.1705–1720 (1994).
    [CrossRef] [PubMed]
  4. R. Webb, G. Hughes, “Detectors for scanning video imagers,” Appl. Opt. 32, 6227–6235 (1993).
    [CrossRef] [PubMed]
  5. S. Jacques, L. Wang, “Monte Carlo modelling of light transport in tissue,” in Optical-Thermal Response of Laser Irradiated Tissue, A. Welch, M. V. Gemert, eds. (Plenum, New York, 1995), Chap. 4, pp. 1–5.
  6. S. Prahl, S. Jacques, A. Welch, “A Monte Carlo model of light propagation in tissue,” in Dosimetry of Laser Radiation in Medicine and Biology, G. J. Mueller, D. H. Sliney, eds. (SPIE Press, Bellingham, Wash., 1989), Vol. ISO5, pp. 102–111.
  7. J. Schmitt, A. Knuttel, M. Yadlowski, “Confocal microscopy in turbid media,” J. Opt. Soc. Am. A 11, 2226–2235 (1994).
    [CrossRef]
  8. W. Cheong, S. Prahl, A. Welch, “A review of the optical properties of biological tissue,” IEEE J. Quantum Electron. 26, 2166–2185 (1990).
    [CrossRef]
  9. T. Wilson, “The role of the pinhole in cofocal imaging systems,” in Handbook of Biological Confocal Microscopy, J. B. Pawley, ed. (Plenum, New York, 1995), Chap. 11, pp. 167–182.
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    [CrossRef] [PubMed]
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    [CrossRef] [PubMed]
  12. I. Vitkin, J. Woolsey, B. Wilson, R. Anderson, “Optical and thermal characterization of natural (sepia oficinalis) melanin,” Photochem. Photobiol. 59, 455–462 (1994).
    [CrossRef] [PubMed]
  13. R. Richards-Kortum, A. Durkin, J. Zeng, “Description and performance of a fiber-optic confocal fluorescence spectrometer,” Appl. Spectrosc. 48, 350–355 (1994).
    [CrossRef]

1995

M. Rajadhyaksha, M. Grossman, D. Esterwitz, R. Webb, R. Anderson, “In vivo confocal scanning laser microscope of human skin: melanin provides strong contrast,” J. Invest. Dermatol. 104, 946–952 (1995).
[CrossRef] [PubMed]

1994

1993

R. Webb, G. Hughes, “Detectors for scanning video imagers,” Appl. Opt. 32, 6227–6235 (1993).
[CrossRef] [PubMed]

W. Petroll, H. Cavanagh, J. Jester, “Three-dimensional imaging of corneal cells using in vivo confocal microscopy,” J. Microsc. 170, 213–219 (1993).
[CrossRef] [PubMed]

1990

W. Cheong, S. Prahl, A. Welch, “A review of the optical properties of biological tissue,” IEEE J. Quantum Electron. 26, 2166–2185 (1990).
[CrossRef]

Anderson, R.

M. Rajadhyaksha, M. Grossman, D. Esterwitz, R. Webb, R. Anderson, “In vivo confocal scanning laser microscope of human skin: melanin provides strong contrast,” J. Invest. Dermatol. 104, 946–952 (1995).
[CrossRef] [PubMed]

I. Vitkin, J. Woolsey, B. Wilson, R. Anderson, “Optical and thermal characterization of natural (sepia oficinalis) melanin,” Photochem. Photobiol. 59, 455–462 (1994).
[CrossRef] [PubMed]

Cavanagh, H.

W. Petroll, H. Cavanagh, J. Jester, “Three-dimensional imaging of corneal cells using in vivo confocal microscopy,” J. Microsc. 170, 213–219 (1993).
[CrossRef] [PubMed]

Cheong, W.

W. Cheong, S. Prahl, A. Welch, “A review of the optical properties of biological tissue,” IEEE J. Quantum Electron. 26, 2166–2185 (1990).
[CrossRef]

Durkin, A.

Eckhaus, M.

J. Schmitt, A. Knuttel, M. Yadlowski, M. Eckhaus, “Optical-coherence tomography of a dense tissue: statistics of attenuation and backscattering,” Phys. Med. Biol.1705–1720 (1994).
[CrossRef] [PubMed]

Esterwitz, D.

M. Rajadhyaksha, M. Grossman, D. Esterwitz, R. Webb, R. Anderson, “In vivo confocal scanning laser microscope of human skin: melanin provides strong contrast,” J. Invest. Dermatol. 104, 946–952 (1995).
[CrossRef] [PubMed]

Fantini, S.

Franceschini, M.

Gratton, E.

Grossman, M.

M. Rajadhyaksha, M. Grossman, D. Esterwitz, R. Webb, R. Anderson, “In vivo confocal scanning laser microscope of human skin: melanin provides strong contrast,” J. Invest. Dermatol. 104, 946–952 (1995).
[CrossRef] [PubMed]

Hughes, G.

Jacques, S.

S. Jacques, L. Wang, “Monte Carlo modelling of light transport in tissue,” in Optical-Thermal Response of Laser Irradiated Tissue, A. Welch, M. V. Gemert, eds. (Plenum, New York, 1995), Chap. 4, pp. 1–5.

S. Prahl, S. Jacques, A. Welch, “A Monte Carlo model of light propagation in tissue,” in Dosimetry of Laser Radiation in Medicine and Biology, G. J. Mueller, D. H. Sliney, eds. (SPIE Press, Bellingham, Wash., 1989), Vol. ISO5, pp. 102–111.

Jester, J.

W. Petroll, H. Cavanagh, J. Jester, “Three-dimensional imaging of corneal cells using in vivo confocal microscopy,” J. Microsc. 170, 213–219 (1993).
[CrossRef] [PubMed]

Knuttel, A.

J. Schmitt, A. Knuttel, M. Yadlowski, M. Eckhaus, “Optical-coherence tomography of a dense tissue: statistics of attenuation and backscattering,” Phys. Med. Biol.1705–1720 (1994).
[CrossRef] [PubMed]

J. Schmitt, A. Knuttel, M. Yadlowski, “Confocal microscopy in turbid media,” J. Opt. Soc. Am. A 11, 2226–2235 (1994).
[CrossRef]

Maier, J.

Petroll, W.

W. Petroll, H. Cavanagh, J. Jester, “Three-dimensional imaging of corneal cells using in vivo confocal microscopy,” J. Microsc. 170, 213–219 (1993).
[CrossRef] [PubMed]

Prahl, S.

W. Cheong, S. Prahl, A. Welch, “A review of the optical properties of biological tissue,” IEEE J. Quantum Electron. 26, 2166–2185 (1990).
[CrossRef]

S. Prahl, S. Jacques, A. Welch, “A Monte Carlo model of light propagation in tissue,” in Dosimetry of Laser Radiation in Medicine and Biology, G. J. Mueller, D. H. Sliney, eds. (SPIE Press, Bellingham, Wash., 1989), Vol. ISO5, pp. 102–111.

Rajadhyaksha, M.

M. Rajadhyaksha, M. Grossman, D. Esterwitz, R. Webb, R. Anderson, “In vivo confocal scanning laser microscope of human skin: melanin provides strong contrast,” J. Invest. Dermatol. 104, 946–952 (1995).
[CrossRef] [PubMed]

Richards-Kortum, R.

Sandison, D.

Schmitt, J.

J. Schmitt, A. Knuttel, M. Yadlowski, “Confocal microscopy in turbid media,” J. Opt. Soc. Am. A 11, 2226–2235 (1994).
[CrossRef]

J. Schmitt, A. Knuttel, M. Yadlowski, M. Eckhaus, “Optical-coherence tomography of a dense tissue: statistics of attenuation and backscattering,” Phys. Med. Biol.1705–1720 (1994).
[CrossRef] [PubMed]

Vitkin, I.

I. Vitkin, J. Woolsey, B. Wilson, R. Anderson, “Optical and thermal characterization of natural (sepia oficinalis) melanin,” Photochem. Photobiol. 59, 455–462 (1994).
[CrossRef] [PubMed]

Walker, S.

Wang, L.

S. Jacques, L. Wang, “Monte Carlo modelling of light transport in tissue,” in Optical-Thermal Response of Laser Irradiated Tissue, A. Welch, M. V. Gemert, eds. (Plenum, New York, 1995), Chap. 4, pp. 1–5.

Webb, R.

M. Rajadhyaksha, M. Grossman, D. Esterwitz, R. Webb, R. Anderson, “In vivo confocal scanning laser microscope of human skin: melanin provides strong contrast,” J. Invest. Dermatol. 104, 946–952 (1995).
[CrossRef] [PubMed]

R. Webb, G. Hughes, “Detectors for scanning video imagers,” Appl. Opt. 32, 6227–6235 (1993).
[CrossRef] [PubMed]

Webb, W.

Welch, A.

W. Cheong, S. Prahl, A. Welch, “A review of the optical properties of biological tissue,” IEEE J. Quantum Electron. 26, 2166–2185 (1990).
[CrossRef]

S. Prahl, S. Jacques, A. Welch, “A Monte Carlo model of light propagation in tissue,” in Dosimetry of Laser Radiation in Medicine and Biology, G. J. Mueller, D. H. Sliney, eds. (SPIE Press, Bellingham, Wash., 1989), Vol. ISO5, pp. 102–111.

Wilson, B.

I. Vitkin, J. Woolsey, B. Wilson, R. Anderson, “Optical and thermal characterization of natural (sepia oficinalis) melanin,” Photochem. Photobiol. 59, 455–462 (1994).
[CrossRef] [PubMed]

Wilson, T.

T. Wilson, “The role of the pinhole in cofocal imaging systems,” in Handbook of Biological Confocal Microscopy, J. B. Pawley, ed. (Plenum, New York, 1995), Chap. 11, pp. 167–182.

Woolsey, J.

I. Vitkin, J. Woolsey, B. Wilson, R. Anderson, “Optical and thermal characterization of natural (sepia oficinalis) melanin,” Photochem. Photobiol. 59, 455–462 (1994).
[CrossRef] [PubMed]

Yadlowski, M.

J. Schmitt, A. Knuttel, M. Yadlowski, “Confocal microscopy in turbid media,” J. Opt. Soc. Am. A 11, 2226–2235 (1994).
[CrossRef]

J. Schmitt, A. Knuttel, M. Yadlowski, M. Eckhaus, “Optical-coherence tomography of a dense tissue: statistics of attenuation and backscattering,” Phys. Med. Biol.1705–1720 (1994).
[CrossRef] [PubMed]

Zeng, J.

Appl. Opt.

Appl. Spectrosc.

IEEE J. Quantum Electron.

W. Cheong, S. Prahl, A. Welch, “A review of the optical properties of biological tissue,” IEEE J. Quantum Electron. 26, 2166–2185 (1990).
[CrossRef]

J. Invest. Dermatol.

M. Rajadhyaksha, M. Grossman, D. Esterwitz, R. Webb, R. Anderson, “In vivo confocal scanning laser microscope of human skin: melanin provides strong contrast,” J. Invest. Dermatol. 104, 946–952 (1995).
[CrossRef] [PubMed]

J. Microsc.

W. Petroll, H. Cavanagh, J. Jester, “Three-dimensional imaging of corneal cells using in vivo confocal microscopy,” J. Microsc. 170, 213–219 (1993).
[CrossRef] [PubMed]

J. Opt. Soc. Am. A

Opt. Lett.

Photochem. Photobiol.

I. Vitkin, J. Woolsey, B. Wilson, R. Anderson, “Optical and thermal characterization of natural (sepia oficinalis) melanin,” Photochem. Photobiol. 59, 455–462 (1994).
[CrossRef] [PubMed]

Phys. Med. Biol.

J. Schmitt, A. Knuttel, M. Yadlowski, M. Eckhaus, “Optical-coherence tomography of a dense tissue: statistics of attenuation and backscattering,” Phys. Med. Biol.1705–1720 (1994).
[CrossRef] [PubMed]

Other

S. Jacques, L. Wang, “Monte Carlo modelling of light transport in tissue,” in Optical-Thermal Response of Laser Irradiated Tissue, A. Welch, M. V. Gemert, eds. (Plenum, New York, 1995), Chap. 4, pp. 1–5.

S. Prahl, S. Jacques, A. Welch, “A Monte Carlo model of light propagation in tissue,” in Dosimetry of Laser Radiation in Medicine and Biology, G. J. Mueller, D. H. Sliney, eds. (SPIE Press, Bellingham, Wash., 1989), Vol. ISO5, pp. 102–111.

T. Wilson, “The role of the pinhole in cofocal imaging systems,” in Handbook of Biological Confocal Microscopy, J. B. Pawley, ed. (Plenum, New York, 1995), Chap. 11, pp. 167–182.

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Figures (10)

Fig. 1
Fig. 1

Confocal geometry for the Monte Carlo simulation. The optical properties of the object layer are varied whereas the properties of the top and bottom layers are matched and constant.

Fig. 2
Fig. 2

Signal-to-background ratio as a function of the focal-plane depth in the tissue with the object layer located at a depth of 100 μm (1 OD) for a range of index mismatches. The value for Δn on each curve indicates the refractive-index mismatch between the object layer and the surrounding layers. Inset: expanded view of the case in which Δn = 0.05.

Fig. 3
Fig. 3

Signal-to-background ratio as a function of the focal-plane depth in the tissue with the object layer located at a depth of 300 μm (3 OD) for a range of index mismatches.

Fig. 4
Fig. 4

Signal-to-background ratio resulting from changes in the scattering coefficient of the object layer. The mismatch in the scattering coefficient indicated on each curve is the difference in scattering between the object layer and the surrounding layers (μ s 1 = 100 cm−1). The front surface of the object layer is located at a depth of 100 μm (1 OD).

Fig. 5
Fig. 5

Signal-to-background ratio resulting from changes in the scattering coefficient between the layers. The scattering indicated on each curve is the difference between the object layer and the surrounding layers (μ s 1 = 100 cm−1). The front surface of the object layer is located at a depth of 300 μm (3 OD).

Fig. 6
Fig. 6

Signal-to-background ratio with a highly absorbing object layer. The object layer is located at a depth of 100 μm (1 OD).

Fig. 7
Fig. 7

Contrast as a function of the increase in refractive index, Δn = n 2n 1, with the object layer at three different depths [100 μm (1 OD), 200 μm (2 OD), 300 μm (3 OD)].

Fig. 8
Fig. 8

Contrast as a function of change in scattering, Δμ s = μ s 2 = μ s 1, with the object layer at three different depths [100 μm (1 OD), 200 μm (2 OD), 300 μm (3 OD2)].

Fig. 9
Fig. 9

Contrast as a function of change in absorption with the object layer at three different depths [100 μm (1 OD), 200 μm (2 OD), 300 μm (3 OD)].

Fig. 10
Fig. 10

Comparison of contrast produced by changes in the refractive index, scattering, and absorption at 1 OD. The arrows represent changes likely to be encountered in actual tissue.

Tables (1)

Tables Icon

Table 1 Range of Optical Properties Used in Monte Carlo Simulation

Equations (6)

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x = r s [ ln ( 1 ξ ) / 2 ] 1 / 2 , y = 0 , z = 0 ,
r s = D 2 ( 1 h f ) ,
μ x = x ( x 2 + z f 2 ) 1 / 2 , μ y = 0 , μ z = z f ( x 2 + z f 2 ) 1 / 2 ,
z f = ( 1 h f ) { [ ( D 2 ) 2 + f 2 ] ( n 1 n air ) 2 ( D 2 ) 2 } 1 / 2 ,
OD = 1 μ t = 1 μ s + μ a .
contrast = P s P b P s + P b ,

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