Abstract

Fluorescence spectra of turbid media depend on the geometry of excitation and collection. The geometry dependence of 476-nm excited fluorescence of the human arterial wall was investigated both experimentally and with a Monte Carlo simulation. Optical properties and the fluorescence yield of each of the three arterial layers were determined. Attenuation of fluorescence by wavelength dependent scattering and reabsorption causes the fluorescence spectra observed at the tissue surface to change with distance from the excitation beam. The ratio of 600-nm fluorescence to 580-nm fluorescence increases significantly beyond the excitation beam. This ratio depends on the amount of oxyhemoglobin in the sample, illustrating how reabsorption can influence autofluorescence measurements. The effects of different excitation/collection geometries on fluorescence spectra are discussed in relation to the design of catheters to differentiate normal and pathologic tissues.

© 1989 Optical Society of America

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References

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  1. C. Kittrell, R. L. Willett, C. de las Santos-Pacheo, N. B. Ratliff, J. R. Kramer, E. G. Malk, M. S. Feld, “Diagnosis of Fibrous Arterial Atherosclerosis Using Fluorescence,” Appl. Opt. 24, 2280–2281 (1985).
    [CrossRef] [PubMed]
  2. M. Sartori, R. Sauerbrey, S. Kubodera, F. K. Tittel, R. Roberts, P. D. Henry, “Autofluorescence Maps of Atherosclerotic Human Arteries: A New Technique in Medical Imaging,” IEEE J. Quantum Electron. QE-23, 1794–1797 (1987).
    [CrossRef]
  3. L. I. Deckelbaum, J. K. Lam, H. S. Cabin, K. S. Clubb, M. B. Long, “Discrimination of Normal and Atherosclerotic Aorta by Laser-Induced Fluorescence,” Lasers Surg. Med. 7, 330–335 (1987).
    [CrossRef] [PubMed]
  4. M. B. Leon et al., “Human Arterial Surface Fluorescence: Atherosclerotic Plaque Identification and Effects of Laser Atheroma Ablation,” J. Am. Coll. Cardiol. 12, 94–102 (1988).
    [CrossRef] [PubMed]
  5. R. Richards-Kortum et al., “A Model for Extraction of Diagnostic Information from Laser Induced Fluorescence Spectra of Human Artery Wall,” Spectrochim. Acta (in press) 454, 89–93 (1989).
  6. R. Richards-Kortum et al., “Spectral Diagnosis of Atherosclerosis Using an Optical Fiber Laser Catheter,” (submitted).
  7. A. A. Oreavsky, V. S. Letokhov, S. E. Ragimov, V. G. Omel'Yanenko, A. A. Belyaev, B. V. Shekhonin, R. S. Akchurin, “Spectral Properties of Human Atherosclerotic Blood Vessel Walls,” Lasers Life Sci. 2, 275–288 (1988).
  8. R. Richards-Kortum, “Understanding Laser Induced Fluorescence of Human Artery Wall with Applications to Diagnosis of Atherosclerosis,” Master's Thesis, Physics Department, Massachusetts Institute of Technology, Cambridge (1987).
  9. S. L. Jacques, S. A Prahl, “Modeling Optical and Thermal Distributions in Tissue During Laser Irradiation,” Lasers Surg. Med. 6, 494–503 (1987).
    [CrossRef] [PubMed]
  10. J. H. Joseph, W. J. Wiscombe, “The Delta-Eddington Approximation for Radiative Flux Transfer,” J. Atmos. Sci. 33, 2452–2459 (1976).
    [CrossRef]
  11. S. A. Prahl, “Light Transport in Tissue,” Ph.D. Thesis, Department of Biomedical Engineering, The University of Texas at Austin (1988).
  12. X. X. Robbins, Pathologic Basis of Disease (WB Saunders, Philadelphia, 1984).
  13. R. R. Anderson, J. A. Parrish, “The Optics of Human Skin,” J. Invest. Dermatol. 77, 13–19 (1981).
    [CrossRef] [PubMed]
  14. G. H. M. Gijsbers, D. Breederveld, M. J. C. van Gemert, T. A. Boon, J. Langelaar, R. P. H. Rettschnick, “In Vivo Fluorescence Excitation and Emission Spectra of Hematoporphyrin-Derivative,” Lasers Life Sci. 1, 28–48 (1986).
  15. I. B. Berlman, Handbook of Fluorescence Spectra of Aromatic Molecules (Academic, New York, 1971).
  16. M. Keijzer, S. L. Jacques, S. A. Prahl, A. J. Welch, “Light Distributions in Artery Tissue: Monte Carlo Simulations for Finite-Diameter Laser Beams,” Lasers Surg. Med. 9, 148–154 (1989).
    [CrossRef] [PubMed]
  17. S. L. Jacques, M. Keijzer, J. P. A. Marijnissen, W. M. Star, “Light Distributions in Phantom Tissues: Theory Meets Experiment,” (submitted Lasers Surg. Med.).
  18. A. N. Witt, “Multiple Scattering in Reflection Nebulae III. Nebulae with Embedded Illuminating Stars,” Astrophys. J. Suppl. 35, 21–29 (1977).
    [CrossRef]

1989 (1)

M. Keijzer, S. L. Jacques, S. A. Prahl, A. J. Welch, “Light Distributions in Artery Tissue: Monte Carlo Simulations for Finite-Diameter Laser Beams,” Lasers Surg. Med. 9, 148–154 (1989).
[CrossRef] [PubMed]

1988 (2)

M. B. Leon et al., “Human Arterial Surface Fluorescence: Atherosclerotic Plaque Identification and Effects of Laser Atheroma Ablation,” J. Am. Coll. Cardiol. 12, 94–102 (1988).
[CrossRef] [PubMed]

A. A. Oreavsky, V. S. Letokhov, S. E. Ragimov, V. G. Omel'Yanenko, A. A. Belyaev, B. V. Shekhonin, R. S. Akchurin, “Spectral Properties of Human Atherosclerotic Blood Vessel Walls,” Lasers Life Sci. 2, 275–288 (1988).

1987 (3)

S. L. Jacques, S. A Prahl, “Modeling Optical and Thermal Distributions in Tissue During Laser Irradiation,” Lasers Surg. Med. 6, 494–503 (1987).
[CrossRef] [PubMed]

M. Sartori, R. Sauerbrey, S. Kubodera, F. K. Tittel, R. Roberts, P. D. Henry, “Autofluorescence Maps of Atherosclerotic Human Arteries: A New Technique in Medical Imaging,” IEEE J. Quantum Electron. QE-23, 1794–1797 (1987).
[CrossRef]

L. I. Deckelbaum, J. K. Lam, H. S. Cabin, K. S. Clubb, M. B. Long, “Discrimination of Normal and Atherosclerotic Aorta by Laser-Induced Fluorescence,” Lasers Surg. Med. 7, 330–335 (1987).
[CrossRef] [PubMed]

1986 (1)

G. H. M. Gijsbers, D. Breederveld, M. J. C. van Gemert, T. A. Boon, J. Langelaar, R. P. H. Rettschnick, “In Vivo Fluorescence Excitation and Emission Spectra of Hematoporphyrin-Derivative,” Lasers Life Sci. 1, 28–48 (1986).

1985 (1)

1981 (1)

R. R. Anderson, J. A. Parrish, “The Optics of Human Skin,” J. Invest. Dermatol. 77, 13–19 (1981).
[CrossRef] [PubMed]

1977 (1)

A. N. Witt, “Multiple Scattering in Reflection Nebulae III. Nebulae with Embedded Illuminating Stars,” Astrophys. J. Suppl. 35, 21–29 (1977).
[CrossRef]

1976 (1)

J. H. Joseph, W. J. Wiscombe, “The Delta-Eddington Approximation for Radiative Flux Transfer,” J. Atmos. Sci. 33, 2452–2459 (1976).
[CrossRef]

Akchurin, R. S.

A. A. Oreavsky, V. S. Letokhov, S. E. Ragimov, V. G. Omel'Yanenko, A. A. Belyaev, B. V. Shekhonin, R. S. Akchurin, “Spectral Properties of Human Atherosclerotic Blood Vessel Walls,” Lasers Life Sci. 2, 275–288 (1988).

Anderson, R. R.

R. R. Anderson, J. A. Parrish, “The Optics of Human Skin,” J. Invest. Dermatol. 77, 13–19 (1981).
[CrossRef] [PubMed]

Belyaev, A. A.

A. A. Oreavsky, V. S. Letokhov, S. E. Ragimov, V. G. Omel'Yanenko, A. A. Belyaev, B. V. Shekhonin, R. S. Akchurin, “Spectral Properties of Human Atherosclerotic Blood Vessel Walls,” Lasers Life Sci. 2, 275–288 (1988).

Berlman, I. B.

I. B. Berlman, Handbook of Fluorescence Spectra of Aromatic Molecules (Academic, New York, 1971).

Boon, T. A.

G. H. M. Gijsbers, D. Breederveld, M. J. C. van Gemert, T. A. Boon, J. Langelaar, R. P. H. Rettschnick, “In Vivo Fluorescence Excitation and Emission Spectra of Hematoporphyrin-Derivative,” Lasers Life Sci. 1, 28–48 (1986).

Breederveld, D.

G. H. M. Gijsbers, D. Breederveld, M. J. C. van Gemert, T. A. Boon, J. Langelaar, R. P. H. Rettschnick, “In Vivo Fluorescence Excitation and Emission Spectra of Hematoporphyrin-Derivative,” Lasers Life Sci. 1, 28–48 (1986).

Cabin, H. S.

L. I. Deckelbaum, J. K. Lam, H. S. Cabin, K. S. Clubb, M. B. Long, “Discrimination of Normal and Atherosclerotic Aorta by Laser-Induced Fluorescence,” Lasers Surg. Med. 7, 330–335 (1987).
[CrossRef] [PubMed]

Clubb, K. S.

L. I. Deckelbaum, J. K. Lam, H. S. Cabin, K. S. Clubb, M. B. Long, “Discrimination of Normal and Atherosclerotic Aorta by Laser-Induced Fluorescence,” Lasers Surg. Med. 7, 330–335 (1987).
[CrossRef] [PubMed]

de las Santos-Pacheo, C.

Deckelbaum, L. I.

L. I. Deckelbaum, J. K. Lam, H. S. Cabin, K. S. Clubb, M. B. Long, “Discrimination of Normal and Atherosclerotic Aorta by Laser-Induced Fluorescence,” Lasers Surg. Med. 7, 330–335 (1987).
[CrossRef] [PubMed]

Feld, M. S.

Gijsbers, G. H. M.

G. H. M. Gijsbers, D. Breederveld, M. J. C. van Gemert, T. A. Boon, J. Langelaar, R. P. H. Rettschnick, “In Vivo Fluorescence Excitation and Emission Spectra of Hematoporphyrin-Derivative,” Lasers Life Sci. 1, 28–48 (1986).

Henry, P. D.

M. Sartori, R. Sauerbrey, S. Kubodera, F. K. Tittel, R. Roberts, P. D. Henry, “Autofluorescence Maps of Atherosclerotic Human Arteries: A New Technique in Medical Imaging,” IEEE J. Quantum Electron. QE-23, 1794–1797 (1987).
[CrossRef]

Jacques, S. L.

M. Keijzer, S. L. Jacques, S. A. Prahl, A. J. Welch, “Light Distributions in Artery Tissue: Monte Carlo Simulations for Finite-Diameter Laser Beams,” Lasers Surg. Med. 9, 148–154 (1989).
[CrossRef] [PubMed]

S. L. Jacques, S. A Prahl, “Modeling Optical and Thermal Distributions in Tissue During Laser Irradiation,” Lasers Surg. Med. 6, 494–503 (1987).
[CrossRef] [PubMed]

S. L. Jacques, M. Keijzer, J. P. A. Marijnissen, W. M. Star, “Light Distributions in Phantom Tissues: Theory Meets Experiment,” (submitted Lasers Surg. Med.).

Joseph, J. H.

J. H. Joseph, W. J. Wiscombe, “The Delta-Eddington Approximation for Radiative Flux Transfer,” J. Atmos. Sci. 33, 2452–2459 (1976).
[CrossRef]

Keijzer, M.

M. Keijzer, S. L. Jacques, S. A. Prahl, A. J. Welch, “Light Distributions in Artery Tissue: Monte Carlo Simulations for Finite-Diameter Laser Beams,” Lasers Surg. Med. 9, 148–154 (1989).
[CrossRef] [PubMed]

S. L. Jacques, M. Keijzer, J. P. A. Marijnissen, W. M. Star, “Light Distributions in Phantom Tissues: Theory Meets Experiment,” (submitted Lasers Surg. Med.).

Kittrell, C.

Kramer, J. R.

Kubodera, S.

M. Sartori, R. Sauerbrey, S. Kubodera, F. K. Tittel, R. Roberts, P. D. Henry, “Autofluorescence Maps of Atherosclerotic Human Arteries: A New Technique in Medical Imaging,” IEEE J. Quantum Electron. QE-23, 1794–1797 (1987).
[CrossRef]

Lam, J. K.

L. I. Deckelbaum, J. K. Lam, H. S. Cabin, K. S. Clubb, M. B. Long, “Discrimination of Normal and Atherosclerotic Aorta by Laser-Induced Fluorescence,” Lasers Surg. Med. 7, 330–335 (1987).
[CrossRef] [PubMed]

Langelaar, J.

G. H. M. Gijsbers, D. Breederveld, M. J. C. van Gemert, T. A. Boon, J. Langelaar, R. P. H. Rettschnick, “In Vivo Fluorescence Excitation and Emission Spectra of Hematoporphyrin-Derivative,” Lasers Life Sci. 1, 28–48 (1986).

Leon, M. B.

M. B. Leon et al., “Human Arterial Surface Fluorescence: Atherosclerotic Plaque Identification and Effects of Laser Atheroma Ablation,” J. Am. Coll. Cardiol. 12, 94–102 (1988).
[CrossRef] [PubMed]

Letokhov, V. S.

A. A. Oreavsky, V. S. Letokhov, S. E. Ragimov, V. G. Omel'Yanenko, A. A. Belyaev, B. V. Shekhonin, R. S. Akchurin, “Spectral Properties of Human Atherosclerotic Blood Vessel Walls,” Lasers Life Sci. 2, 275–288 (1988).

Long, M. B.

L. I. Deckelbaum, J. K. Lam, H. S. Cabin, K. S. Clubb, M. B. Long, “Discrimination of Normal and Atherosclerotic Aorta by Laser-Induced Fluorescence,” Lasers Surg. Med. 7, 330–335 (1987).
[CrossRef] [PubMed]

Malk, E. G.

Marijnissen, J. P. A.

S. L. Jacques, M. Keijzer, J. P. A. Marijnissen, W. M. Star, “Light Distributions in Phantom Tissues: Theory Meets Experiment,” (submitted Lasers Surg. Med.).

Omel'Yanenko, V. G.

A. A. Oreavsky, V. S. Letokhov, S. E. Ragimov, V. G. Omel'Yanenko, A. A. Belyaev, B. V. Shekhonin, R. S. Akchurin, “Spectral Properties of Human Atherosclerotic Blood Vessel Walls,” Lasers Life Sci. 2, 275–288 (1988).

Oreavsky, A. A.

A. A. Oreavsky, V. S. Letokhov, S. E. Ragimov, V. G. Omel'Yanenko, A. A. Belyaev, B. V. Shekhonin, R. S. Akchurin, “Spectral Properties of Human Atherosclerotic Blood Vessel Walls,” Lasers Life Sci. 2, 275–288 (1988).

Parrish, J. A.

R. R. Anderson, J. A. Parrish, “The Optics of Human Skin,” J. Invest. Dermatol. 77, 13–19 (1981).
[CrossRef] [PubMed]

Prahl, S. A

S. L. Jacques, S. A Prahl, “Modeling Optical and Thermal Distributions in Tissue During Laser Irradiation,” Lasers Surg. Med. 6, 494–503 (1987).
[CrossRef] [PubMed]

Prahl, S. A.

M. Keijzer, S. L. Jacques, S. A. Prahl, A. J. Welch, “Light Distributions in Artery Tissue: Monte Carlo Simulations for Finite-Diameter Laser Beams,” Lasers Surg. Med. 9, 148–154 (1989).
[CrossRef] [PubMed]

S. A. Prahl, “Light Transport in Tissue,” Ph.D. Thesis, Department of Biomedical Engineering, The University of Texas at Austin (1988).

Ragimov, S. E.

A. A. Oreavsky, V. S. Letokhov, S. E. Ragimov, V. G. Omel'Yanenko, A. A. Belyaev, B. V. Shekhonin, R. S. Akchurin, “Spectral Properties of Human Atherosclerotic Blood Vessel Walls,” Lasers Life Sci. 2, 275–288 (1988).

Ratliff, N. B.

Rettschnick, R. P. H.

G. H. M. Gijsbers, D. Breederveld, M. J. C. van Gemert, T. A. Boon, J. Langelaar, R. P. H. Rettschnick, “In Vivo Fluorescence Excitation and Emission Spectra of Hematoporphyrin-Derivative,” Lasers Life Sci. 1, 28–48 (1986).

Richards-Kortum, R.

R. Richards-Kortum et al., “A Model for Extraction of Diagnostic Information from Laser Induced Fluorescence Spectra of Human Artery Wall,” Spectrochim. Acta (in press) 454, 89–93 (1989).

R. Richards-Kortum et al., “Spectral Diagnosis of Atherosclerosis Using an Optical Fiber Laser Catheter,” (submitted).

R. Richards-Kortum, “Understanding Laser Induced Fluorescence of Human Artery Wall with Applications to Diagnosis of Atherosclerosis,” Master's Thesis, Physics Department, Massachusetts Institute of Technology, Cambridge (1987).

Robbins, X. X.

X. X. Robbins, Pathologic Basis of Disease (WB Saunders, Philadelphia, 1984).

Roberts, R.

M. Sartori, R. Sauerbrey, S. Kubodera, F. K. Tittel, R. Roberts, P. D. Henry, “Autofluorescence Maps of Atherosclerotic Human Arteries: A New Technique in Medical Imaging,” IEEE J. Quantum Electron. QE-23, 1794–1797 (1987).
[CrossRef]

Sartori, M.

M. Sartori, R. Sauerbrey, S. Kubodera, F. K. Tittel, R. Roberts, P. D. Henry, “Autofluorescence Maps of Atherosclerotic Human Arteries: A New Technique in Medical Imaging,” IEEE J. Quantum Electron. QE-23, 1794–1797 (1987).
[CrossRef]

Sauerbrey, R.

M. Sartori, R. Sauerbrey, S. Kubodera, F. K. Tittel, R. Roberts, P. D. Henry, “Autofluorescence Maps of Atherosclerotic Human Arteries: A New Technique in Medical Imaging,” IEEE J. Quantum Electron. QE-23, 1794–1797 (1987).
[CrossRef]

Shekhonin, B. V.

A. A. Oreavsky, V. S. Letokhov, S. E. Ragimov, V. G. Omel'Yanenko, A. A. Belyaev, B. V. Shekhonin, R. S. Akchurin, “Spectral Properties of Human Atherosclerotic Blood Vessel Walls,” Lasers Life Sci. 2, 275–288 (1988).

Star, W. M.

S. L. Jacques, M. Keijzer, J. P. A. Marijnissen, W. M. Star, “Light Distributions in Phantom Tissues: Theory Meets Experiment,” (submitted Lasers Surg. Med.).

Tittel, F. K.

M. Sartori, R. Sauerbrey, S. Kubodera, F. K. Tittel, R. Roberts, P. D. Henry, “Autofluorescence Maps of Atherosclerotic Human Arteries: A New Technique in Medical Imaging,” IEEE J. Quantum Electron. QE-23, 1794–1797 (1987).
[CrossRef]

van Gemert, M. J. C.

G. H. M. Gijsbers, D. Breederveld, M. J. C. van Gemert, T. A. Boon, J. Langelaar, R. P. H. Rettschnick, “In Vivo Fluorescence Excitation and Emission Spectra of Hematoporphyrin-Derivative,” Lasers Life Sci. 1, 28–48 (1986).

Welch, A. J.

M. Keijzer, S. L. Jacques, S. A. Prahl, A. J. Welch, “Light Distributions in Artery Tissue: Monte Carlo Simulations for Finite-Diameter Laser Beams,” Lasers Surg. Med. 9, 148–154 (1989).
[CrossRef] [PubMed]

Willett, R. L.

Wiscombe, W. J.

J. H. Joseph, W. J. Wiscombe, “The Delta-Eddington Approximation for Radiative Flux Transfer,” J. Atmos. Sci. 33, 2452–2459 (1976).
[CrossRef]

Witt, A. N.

A. N. Witt, “Multiple Scattering in Reflection Nebulae III. Nebulae with Embedded Illuminating Stars,” Astrophys. J. Suppl. 35, 21–29 (1977).
[CrossRef]

Appl. Opt. (1)

Astrophys. J. Suppl. (1)

A. N. Witt, “Multiple Scattering in Reflection Nebulae III. Nebulae with Embedded Illuminating Stars,” Astrophys. J. Suppl. 35, 21–29 (1977).
[CrossRef]

IEEE J. Quantum Electron. (1)

M. Sartori, R. Sauerbrey, S. Kubodera, F. K. Tittel, R. Roberts, P. D. Henry, “Autofluorescence Maps of Atherosclerotic Human Arteries: A New Technique in Medical Imaging,” IEEE J. Quantum Electron. QE-23, 1794–1797 (1987).
[CrossRef]

J. Am. Coll. Cardiol. (1)

M. B. Leon et al., “Human Arterial Surface Fluorescence: Atherosclerotic Plaque Identification and Effects of Laser Atheroma Ablation,” J. Am. Coll. Cardiol. 12, 94–102 (1988).
[CrossRef] [PubMed]

J. Atmos. Sci. (1)

J. H. Joseph, W. J. Wiscombe, “The Delta-Eddington Approximation for Radiative Flux Transfer,” J. Atmos. Sci. 33, 2452–2459 (1976).
[CrossRef]

J. Invest. Dermatol. (1)

R. R. Anderson, J. A. Parrish, “The Optics of Human Skin,” J. Invest. Dermatol. 77, 13–19 (1981).
[CrossRef] [PubMed]

Lasers Life Sci. (2)

G. H. M. Gijsbers, D. Breederveld, M. J. C. van Gemert, T. A. Boon, J. Langelaar, R. P. H. Rettschnick, “In Vivo Fluorescence Excitation and Emission Spectra of Hematoporphyrin-Derivative,” Lasers Life Sci. 1, 28–48 (1986).

A. A. Oreavsky, V. S. Letokhov, S. E. Ragimov, V. G. Omel'Yanenko, A. A. Belyaev, B. V. Shekhonin, R. S. Akchurin, “Spectral Properties of Human Atherosclerotic Blood Vessel Walls,” Lasers Life Sci. 2, 275–288 (1988).

Lasers Surg. Med. (3)

L. I. Deckelbaum, J. K. Lam, H. S. Cabin, K. S. Clubb, M. B. Long, “Discrimination of Normal and Atherosclerotic Aorta by Laser-Induced Fluorescence,” Lasers Surg. Med. 7, 330–335 (1987).
[CrossRef] [PubMed]

M. Keijzer, S. L. Jacques, S. A. Prahl, A. J. Welch, “Light Distributions in Artery Tissue: Monte Carlo Simulations for Finite-Diameter Laser Beams,” Lasers Surg. Med. 9, 148–154 (1989).
[CrossRef] [PubMed]

S. L. Jacques, S. A Prahl, “Modeling Optical and Thermal Distributions in Tissue During Laser Irradiation,” Lasers Surg. Med. 6, 494–503 (1987).
[CrossRef] [PubMed]

Other (7)

S. L. Jacques, M. Keijzer, J. P. A. Marijnissen, W. M. Star, “Light Distributions in Phantom Tissues: Theory Meets Experiment,” (submitted Lasers Surg. Med.).

I. B. Berlman, Handbook of Fluorescence Spectra of Aromatic Molecules (Academic, New York, 1971).

R. Richards-Kortum et al., “A Model for Extraction of Diagnostic Information from Laser Induced Fluorescence Spectra of Human Artery Wall,” Spectrochim. Acta (in press) 454, 89–93 (1989).

R. Richards-Kortum et al., “Spectral Diagnosis of Atherosclerosis Using an Optical Fiber Laser Catheter,” (submitted).

R. Richards-Kortum, “Understanding Laser Induced Fluorescence of Human Artery Wall with Applications to Diagnosis of Atherosclerosis,” Master's Thesis, Physics Department, Massachusetts Institute of Technology, Cambridge (1987).

S. A. Prahl, “Light Transport in Tissue,” Ph.D. Thesis, Department of Biomedical Engineering, The University of Texas at Austin (1988).

X. X. Robbins, Pathologic Basis of Disease (WB Saunders, Philadelphia, 1984).

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Figures (7)

Fig. 1
Fig. 1

The 476-nm-induced fluorescence spectra from a normal human cadaver aorta N and from one with atheromatous plaque P.6,8 Fluorescence spectra were collected from two areas: the tissue surface area directly illuminated by the excitation beam, which has a diameter of 1 mm (left); and the ring around the directly illuminated area, with a 1-mm i.d. and 2-mm o.d. (right). For the normal aorta the ratio of the fluorescence intensity at 600 and 580 nm was 1.27 for the directly illuminated circle and 1.72 for the ring around it. For the atheromatous plaque, the ratios were 0.91 for both collection areas.

Fig. 2
Fig. 2

Optical properties of the normal human aorta vs wavelength averaged over three samples: the absorption coefficient μa; the scattering coefficient μs; and the mean cosine of the scattering angle g. (Over the 300–350-nm range, g-values were estimated.) The variance over the three samples is small for the μs and g spectra.

Fig. 3
Fig. 3

Separate absorption coefficient spectra for the intimas of samples I, II, and III. The spectra indicate different amounts of absorbed oxyhemoglobin in each sample.

Fig. 4
Fig. 4

Intrinsic fluorescence coefficient β with 476-nm excitation of the human aorta (sample III).

Fig. 5
Fig. 5

Experimental setup for the collection of tissue fluorescence spectra. A cw argon-ion laser provides 476-nm excitation light. The pinhole of a spatial filter is imaged at the tissue surface to provide a well-defined 1.0-mm diam excitation spot. Circular areas of the tissue surface with various diameters are imaged at the entrance slit of a scanning monochromator via an image plane with an iris (for exact dimensions see Ref. 8).

Fig. 6
Fig. 6

(A) Distribution of 476-nm excitation light in the sample [Ψ(r)], as generated by the Monte Carlo method. The profile of the excitation beam is chosen to be the same as in the experiments. (B) Escape functions [E(λ,r,z), λ = 580 nm] for fluorescence point sources located at 5-, 25-, 50-, and 100-μm depths in the tissue. (C) Fluorescence at the surface [F(λ,r), λ = 580 nm)] from tissue layers of 10-μm thickness at depths of 5, 25, 50, and 100 μm.

Fig. 7
Fig. 7

(A) F(λ,r), distributions of 580- and 600-nm fluorescence over the surface of sample III as measured (symbols) and as simulated with the Monte Carlo method (lines). (B) R(r) for samples I, II, and III (measurements: symbols; simulations: lines). The ratios Rtot of 600–580-nm fluorescence collected from the total tissue surface are shown on the right: measured: △, +, and ▽; Monte Carlo predictions: ●; and Rtot values reported by Kittrell et al.1: [ ] and [ ].

Tables (1)

Tables Icon

Table I Optical Properties Used in Monte Carlo Simulations of Fluorescence from Samples I, II, and III

Equations (4)

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

F ( λ , r ) = 0 D 0 2 π 0 Ψ ( r , z ) β ( λ , z ) × E ( λ , r 2 + r 2 2 r r cos ϑ , z ) r d r d ϑ d z ,
R ( r ) = F ( 600 nm , r ) F ( 580 nm , r ) .
R tot = 0 F ( 600 nm , r ) rdr 0 F ( 580 nm , r ) rdr .
R total = 1 + 0.014 ( Δ μ a ) 2 ,

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