Abstract

In-vivo imaging can be achieved with a coherent-fiber-bundle based confocal reflectance microscope. Such a microscope could provide the means to detect pre-cancerous lesions in the cervix by characterizing cells’ nuclear-to-cytoplasmic ratio. In this paper we present the design of such a fiber confocal reflectance microscope, with an emphasis on its optical sub-systems. The optical sub-systems consist of a commercially available microscope objective and custom designed telescope, scan lens, and coupling lens systems. The performance of the fiber confocal reflectance microscope was evaluated by imaging a resolution bar target and human cervical biopsy tissues. The results presented in this paper demonstrate a lateral resolution of 2 µm and axial resolution of 6 µm. The sensitivity of the system defined by the smallest refractive-index mismatch that can be detected is approximately Δn~0.05.

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References

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  1. B. Pawley, ed., Handbook of biological confocal microscopy, 2nd ed. (Plenum, New York, 1995).
    [CrossRef]
  2. F. Gmitro and D. Aziz, "Confocal microscopy through a fiber-optic imaging bundle," Opt. Lett. 18, 565-567 (1993).
    [CrossRef] [PubMed]
  3. Knittel, L. Schnieder, G. Buess, B. Messerschmidt, and T. Possner, "Endoscope-compatible confocal microscope using a gradient index-lens system," Opt. Comm. 188, 267-273 (2001).
    [CrossRef]
  4. L. Dickensheets and G. S. Kino, "Silicon-micromachined scanning confocal optical microscope," J. Microelectromech. Syst. 7, 38-47 (1998).
    [CrossRef]
  5. Williams, Cancer biology and management: An introduction (JohnWiley & Sons Ltd., West Sussex, England, 1990).
  6. Smithpeter, A. Dunn, R. Drezek, T. collier, and R. Richards-Kortum, "Near real time confocal microscope of cultured amelanotic cells: sources of signal, contrast agents and limits of contrast," J. Biomed. Opt. 3, 429-436 (1998)
    [CrossRef] [PubMed]
  7. Drezek, T. Collier, C. Brookner, A. Malpica, R. Lotan, R. Richards-Kortum, "Laser scanning confocal microscopy of cervical tissue before and after application of acetic acid," AM J Obstet Gynecol 182, 1135-1139 (2000).
    [CrossRef] [PubMed]
  8. K. Dunn, C. Smithpeter, A. J. Welch, R. Richards-Kortum, "Source of contrast in confocal reflectance imaging," Appl. Opt. 38, 2105-2115 (1999).
  9. S.A., Inc., Santa Clara, California, USA, http://www.sumitomoelectricusa.com.
  10. Yang, G. Wang, J. Wang, Z. Xu, "Influence of fiber terminal face reflection on fiber optic confocal scanning microscope," in 1999 International conference on biomedical optics, Q. Luo, B. Chance, L. V. Wang, S. L. Jacques eds., Proc. SPIE 3863, 332-336 (1999).
    [CrossRef]
  11. , Albuquerque, New Mexico, USA, http://www.lightpath.com.
  12. medivision-net.com.
  13. , Tucson, Arizona, USA, http://www.focus-software.com.
  14. W. Goodman, Introduction to Fourier Optics, 2nd ed. (The McGraw-Hill Companies, Inc., 1996).

Other (14)

B. Pawley, ed., Handbook of biological confocal microscopy, 2nd ed. (Plenum, New York, 1995).
[CrossRef]

F. Gmitro and D. Aziz, "Confocal microscopy through a fiber-optic imaging bundle," Opt. Lett. 18, 565-567 (1993).
[CrossRef] [PubMed]

Knittel, L. Schnieder, G. Buess, B. Messerschmidt, and T. Possner, "Endoscope-compatible confocal microscope using a gradient index-lens system," Opt. Comm. 188, 267-273 (2001).
[CrossRef]

L. Dickensheets and G. S. Kino, "Silicon-micromachined scanning confocal optical microscope," J. Microelectromech. Syst. 7, 38-47 (1998).
[CrossRef]

Williams, Cancer biology and management: An introduction (JohnWiley & Sons Ltd., West Sussex, England, 1990).

Smithpeter, A. Dunn, R. Drezek, T. collier, and R. Richards-Kortum, "Near real time confocal microscope of cultured amelanotic cells: sources of signal, contrast agents and limits of contrast," J. Biomed. Opt. 3, 429-436 (1998)
[CrossRef] [PubMed]

Drezek, T. Collier, C. Brookner, A. Malpica, R. Lotan, R. Richards-Kortum, "Laser scanning confocal microscopy of cervical tissue before and after application of acetic acid," AM J Obstet Gynecol 182, 1135-1139 (2000).
[CrossRef] [PubMed]

K. Dunn, C. Smithpeter, A. J. Welch, R. Richards-Kortum, "Source of contrast in confocal reflectance imaging," Appl. Opt. 38, 2105-2115 (1999).

S.A., Inc., Santa Clara, California, USA, http://www.sumitomoelectricusa.com.

Yang, G. Wang, J. Wang, Z. Xu, "Influence of fiber terminal face reflection on fiber optic confocal scanning microscope," in 1999 International conference on biomedical optics, Q. Luo, B. Chance, L. V. Wang, S. L. Jacques eds., Proc. SPIE 3863, 332-336 (1999).
[CrossRef]

, Albuquerque, New Mexico, USA, http://www.lightpath.com.

medivision-net.com.

, Tucson, Arizona, USA, http://www.focus-software.com.

W. Goodman, Introduction to Fourier Optics, 2nd ed. (The McGraw-Hill Companies, Inc., 1996).

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Figures (9)

Fig. 1.
Fig. 1.

Diagram of components layout of the fiber confocal reflectance microscope.

Fig. 2.
Fig. 2.

Telescope and scan-lens designs. Part (a) shows the optical layout of the telescope. Part (b) shows the optical layout of the scan lens assembly. The color of each ray bundle corresponds to a different field position at the coherent fiber bundle, denoted by h. Blue rays represent on-axis field position, green rays represent h=0.35 mm, and red rays represent h=0.5 mm.

Fig. 3.
Fig. 3.

Geometric spot diagram for the telescope/scan lens system at three different field positions at the coherent fiber bundle, denoted by h. The circle in each diagram represents the size of the diffraction Airy disc. Spot radius values given in the diagram are in micrometers.

Fig. 4.
Fig. 4.

Part (a) shows the focal spot formed by the telescope/scan lens system. The spot diameter is approximately 3.4 µm. Part (b) shows the distal end of the fiber bundle when only one fiber is illuminated by the telescope/scan lens. Dotted circles represent the surrounding fibers.

Fig. 5.
Fig. 5.

Optical layout for the coupling lens system. The color of the ray bundle corresponding different field position. Blue rays represent on axis, green rays represent h=0.35 mm, and red rays represent h=0.5 mm.

Fig. 6.
Fig. 6.

Geometric spot diagrams for the coupling lens system at three different field positions at the coherent fiber bundle, denoted by h. The circle in each diagram represents the size of the diffraction Airy disc. Spot radius values given in the diagram are measured in micrometers

Fig. 7.
Fig. 7.

Image of resolution target taken with the fiber confocal reflectance microscope. The smallest features have line thickness and spacing of approximately 2 µm.

Fig. 8.
Fig. 8.

Reflected signal from imaging a plane mirror as a function of defocus. The FWHM determines the axial resolution and it is approximately 6 µm.

Fig. 9.
Fig. 9.

Confocal image of epithelial cells from cervical biopsies. Part (a) shows normal tissues and part (b) shows abnormal tissues. Acetic acid solution of 6% concentration was used to enhance the contrast. Scale bar indicates 20 µm.

Tables (2)

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Table 1. Prescription data for telescope and scan lens

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Table 2. Prescription data for telescope and coupling lens

Equations (3)

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Lateral resolution = Fiber spacing m microscope objective coupling lens = 1.8 μ m
FOV Scan lens = FOV Microscope objective × m microscope objective Coupling lens 1 mm .
2.44 λ NA = 4.3 μ m

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