L. Thrane

Analysis of optical coherence tomography systems based on the extended Huygens–Fresnel principle

We have developed a new theoretical description of the optical coherence tomography (OCT) technique for imaging in highly scattering tissue. The description is based on the extended Huygens-Fresnel principle, valid in both the single- and multiple-scattering regimes. The so-called shower curtain effect, which manifests itself in a standard OCT system, is an inherent property of the present theory. We demonstrate that the shower curtain effect leads to a strong increase in the heterodyne signal in a standard OCT system. This is in contrast to previous OCT models, where the shower curtain effect was not taken into account. The theoretical analysis is verified by measurements on samples consisting of aqueous suspensions of microspheres. Finally, we discuss the use of our new theoretical model for optimization of the OCT system.

Calculation of the maximum obtainable probing depth of optical coherence tomography in tissue

The maximum probing depth is of considerable interest in the characterization and optimization of an optical coherence tomography (OCT) system when used for imaging in highly scattering tissue. In this paper, we calculate the maximum obtainable probing depth based on the design variables of the OCT system, the detector characteristics, and the optical properties of the tissue. The calculation of the maximum probing depth is based on the minimum acceptable signal-to-noise ratio and a new analytical model of the OCT technique, which is valid in both the single and multiple scattering regimes. The new model is based on the extended Huygens-Fresnel principle and the use of mutual coherence functions. The so-called shower curtain effect, which manifests itself in standard OCT systems, is an inherent property of this model. We demonstrate the utmost importance of including both multiple scattering and the shower curtain effect when calculating the maximum probing in tissue. Furthermore, we show how the maximum probing depth depends on the design variables of the OCT system and the optical properties of the tissue including the reflection characteristics of the probed discontinuity. Finally, experiments are presented verifying the validity of the model used in the calculations.

True-reflection OCT imaging

We present the concept of a so-called true-reflection OCT imaging algorithm. The algorithm is based on a recently developed analytical model of the optical coherence tomography technique, which is valid in both the single and multiple scattering regimes simultaneously. The model is based on the extended Huygens-Fresnel principle and takes into account the so-called shower curtain effect. With this new algorithm, it is possible to reduce the effects of scattering from conventional OCT images and create so-called true-reflection OCT images. This type of postprocessing is similar to the correction for attenuation often used in ultrasonic imaging. The principle of the algorithm is demonstrated experimentally by measurements on a solid phantom. Finally, the reduction of the dynamic range of the data when using the algorithm is an additional advantage of this post processing technique.

The effects of multiple scattering on axial resolution in optical coherence tomography

Summary form only given. OCT axial resolution degrades with increasing optical depth due to multiple scattering. This effect is more pronounced for small than for large values of the longitudinal coherence length, and is an inherent effect of OCT imaging in biological tissue.