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Proceedings Paper

Accurate and quantitative polarization-sensitive OCT by unbiased birefringence estimator with noise-stochastic correction
Author(s): Deepa Kasaragod; Satoshi Sugiyama; Yasushi Ikuno; David Alonso-Caneiro; Masahiro Yamanari; Shinichi Fukuda; Tetsuro Oshika; Young-Joo Hong; En Li; Shuichi Makita; Masahiro Miura; Yoshiaki Yasuno
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Paper Abstract

Polarization sensitive optical coherence tomography (PS-OCT) is a functional extension of OCT that contrasts the polarization properties of tissues. It has been applied to ophthalmology, cardiology, etc. Proper quantitative imaging is required for a widespread clinical utility. However, the conventional method of averaging to improve the signal to noise ratio (SNR) and the contrast of the phase retardation (or birefringence) images introduce a noise bias offset from the true value. This bias reduces the effectiveness of birefringence contrast for a quantitative study. Although coherent averaging of Jones matrix tomography has been widely utilized and has improved the image quality, the fundamental limitation of nonlinear dependency of phase retardation and birefringence to the SNR was not overcome. So the birefringence obtained by PS-OCT was still not accurate for a quantitative imaging.

The nonlinear effect of SNR to phase retardation and birefringence measurement was previously formulated in detail for a Jones matrix OCT (JM-OCT) [1]. Based on this, we had developed a maximum a-posteriori (MAP) estimator and quantitative birefringence imaging was demonstrated [2]. However, this first version of estimator had a theoretical shortcoming. It did not take into account the stochastic nature of SNR of OCT signal.

In this paper, we present an improved version of the MAP estimator which takes into account the stochastic property of SNR. This estimator uses a probability distribution function (PDF) of true local retardation, which is proportional to birefringence, under a specific set of measurements of the birefringence and SNR. The PDF was pre-computed by a Monte-Carlo (MC) simulation based on the mathematical model of JM-OCT before the measurement. A comparison between this new MAP estimator, our previous MAP estimator [2], and the standard mean estimator is presented. The comparisons are performed both by numerical simulation and in vivo measurements of anterior and posterior eye segment as well as in skin imaging. The new estimator shows superior performance and also shows clearer image contrast.

Paper Details

Date Published: 8 March 2016
PDF: 5 pages
Proc. SPIE 9697, Optical Coherence Tomography and Coherence Domain Optical Methods in Biomedicine XX, 96971I (8 March 2016); doi: 10.1117/12.2214527
Show Author Affiliations
Deepa Kasaragod, Univ. of Tsukuba (Japan)
Satoshi Sugiyama, Univ. of Tsukuba (Japan)
Tomey Corp. (Japan)
Yasushi Ikuno, Osaka Univ. Hospital (Japan)
David Alonso-Caneiro, Queensland Univ. of Technology (Australia)
Masahiro Yamanari, Tomey Corp. (Japan)
Shinichi Fukuda, Univ. of Tsukuba (Japan)
Tetsuro Oshika, Univ. of Tsukuba (Japan)
Young-Joo Hong, Univ. of Tsukuba (Japan)
En Li, Univ. of Tsukuba (Japan)
Shuichi Makita, Univ. of Tsukuba (Japan)
Masahiro Miura, Tokyo Medical Univ. (Japan)
Yoshiaki Yasuno, Univ. of Tsukuba (Japan)

Published in SPIE Proceedings Vol. 9697:
Optical Coherence Tomography and Coherence Domain Optical Methods in Biomedicine XX
Joseph A. Izatt; James G. Fujimoto; Valery V. Tuchin, Editor(s)

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