Quantitative comparison of contrast and imaging depth of ultrahigh-resolution optical coherence tomography images in 800-1700 nm wavelength region

Abstract

We investigated the wavelength dependence of imaging depth and clearness of structure in ultrahigh-resolution optical coherence tomography over a wide wavelength range. We quantitatively compared the optical properties of samples using supercontinuum sources at five wavelengths, 800 nm, 1060 nm, 1300 nm, 1550 nm, and 1700 nm, with the same system architecture. For samples of industrially used homogeneous materials with low water absorption, the attenuation coefficients of the samples were fitted using Rayleigh scattering theory. We confirmed that the systems with the longer-wavelength sources had lower scattering coefficients and less dependence on the sample materials. For a biomedical sample, we observed wavelength dependence of the attenuation coefficient, which can be explained by absorption by water and hemoglobin.

Keywords: (110.4500) Optical coherence tomography; (170.3880) Medical and biological imaging.

Figures

Fig. 1

(a) Output spectra of supercontinuum sources together with water absorption spectrum and (b) corresponding theoretical longitudinal resolutions at all wavelengths as a function of bandwidth.

Fig. 2

Experimental setup for time-domain optical coherence tomography.

Fig. 3

(a–e) Interference signals with mirror as sample at (a) 800 nm, (b) 1060 nm, (c) 1300 nm, (d) 1550 nm, and (e) 1700 nm UHR-OCT in air. (f) Observed longitudinal resolutions (circles) together with theoretical predictions (solid lines).

Fig. 4

Observed spatial beam profiles at the top of surface of the sample at all wavelengths.

Fig. 5

(a) Photograph of semiconductor memory card with plastic cover. (b, c) OCT images obtained at (b) 0.8 μm and (c) 1.7 μm. (d–h) Depth profiles averaged over 250 A-line scans and more than 50 iterative measurements at (d) 800 nm, (e) 1060 nm, (f) 1300 nm, (g) 1550 nm, and (h) 1700 nm. The slopes shown by the red lines were used to determine the total attenuation coefficients.

Fig. 6

(a) Photograph of eraser. (b–f) Depth profiles averaged over 250 A-lines and more than 50 iterative measurements at (b) 800 nm, (c) 1060 nm, (d) 1300 nm, (e) 1550 nm, and (f) 1700 nm. The slopes shown by the red lines were used to determine the total attenuation coefficients.

Fig. 7

(a) Photograph of magnet. (b–f) Depth profiles averaged over 250 A-lines and more than 50 iterative measurements at (b) 800 nm, (c) 1060 nm, (d) 1300 nm, (e) 1550 nm, and (f) 1700 nm. The slopes shown by the red lines were used to determine the total attenuation coefficients.

Fig. 8

Wavelength dependence of total attenuation coefficient for industrially used materials

Fig. 9

(a) Photograph of human tooth sample. (b–f) OCT images at red line in (a) and depth profiles obtained at red dashed line in each of the OCT images at (b) 800 nm, (c) 1060 nm, (d) 1300 nm, (e) 1550 nm, and (f) 1700 nm. The slopes shown by the red and blue solid lines were used to determine the total attenuation coefficients. (g) Wavelength dependence of total attenuation coefficients of enamel and dentine layers in the sample. Important features inside the sample can be distinguished, such as the enamel layer (en) and the dentin layer (d).

Fig. 10

(a) Photograph of pig trachea sample. (b–f) OCT images and depth profiles at the red dashed line in each OCT image at (b) 800 nm, (c) 1060 nm, (d) 1300 nm, (e) 1550 nm and (f) 1700 nm . The slopes shown by the solid red lines were used to determine the total attenuation coefficients. (g) Wavelength dependence of total attenuation coefficients of mucosa in trachea. (h) Three-dimensional (3D) image at 1700 nm (Media 1). A 3D image at 800 nm is also shown as a movie in Media 2. Important features inside the sample can be distinguished, such as the epithelium layer (ep), the mucosa layer (m), and cartilage (ca).

Fig. 11

Total attenuation coefficients of (a) industrially used materials and (b) biomedical samples. The absorption coefficients of water [27] and hemoglobin [28] are shown in blue and red lines with arbitrary unit.