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.