Purpose:
Phase retardation (PR) images obtained by polarization sensitive optical coherence tomography (PSOCT) provides valuable information beyond a standard backscattering OCT. E.g., inflammation and fibrosis can alternate the PR property of tissue. However, the ability of PSOCT in quantitative assessment of tissue is degraded by an elaborated noise property, i.e., a significant systematic error indelible for standard noise reduction methods. Our research is aimed at quantitative PR tomography of the posterior eye by using a newly designed PR estimator.
Methods:
The maculae of 8 eyes of 6 normal subjects were scanned by a custom-built PSOCT with 6 mm scan range. Our PSOCT utilizes a swept-source OCT technology with 1 µm wavelength probe, 30,000 A-scans/sec scanning speed and 11 µm depth resolution in tissue. Both intensity and PR tomography can be obtained by single scanning of PSOCT. A Monte-Carlo based PR estimation algorithm is applied to cancel the systematic error. A composite PR OCT, in which the color represents the PR and the brightness represents the intensity, was created. PR images with and without systematic error cancelation were qualitatively compared by a grader.
Results:
Figures (a~c) show the intensity and PR images without and with systematic error cancelation. Although the retinal region is expected to have little birefringence, it appeared as light blue (PR ~ 30 degrees). In contrast, in the error-canceled image (c), the retina appeared as pale green (PR ~ 10 degrees). This efficiency was found in 6 of 8 eyes. Owing to the PR error cancelation and its resulting high contrast PR image, strong PR (yellow) beneath the choroid can be clearly seen in Fig. (c). This was found in 5 of 8 eyes and may indicate the scleral birefringence.
Conclusions:
Exact polarization sensitive OCT of posterior eye was realized by using newly developed error cancelation algorithm. This method promotes the capability of PS-OCT and may enable quantitative assessment of the posterior.
Keywords: imaging/image analysis: clinical • imaging methods (CT, FA, ICG, MRI, OCT, RTA, SLO, ultrasound) • optical properties