Abstract
Multiple scattering in turbid media inhibits optimal light focusing and thus limits the penetration depth in optical coherence tomography (OCT). However, the effects of multiple scattering in a turbid medium can be systematically controlled by shaping the incident wavefront. The authors utilize the reciprocity of Maxwell's equations and finite-difference time-domain numerical analysis to investigate the ultimate performance bounds of wavefront shaping-OCT under ideal and realistic configurations and compare them with the conventional method. The results reveal that the optimized impinging wavefront significantly enhances the penetration depth of OCT.
Highlights
Scattering of waves due to inhomogeneous material compositions is a fundamental physical phenomenon on which most imaging methodologies, from seismology to medical imaging, are based
Wavefront shaping-optical coherence tomography (OCT) can be regarded as an application of one of the well-known fundamental properties of Maxwell’s equations, Lorentz reciprocity, which applies to the propagation and scattering of electromagnetic waves in reciprocal media of arbitrary morphology [31]
We have quantitatively investigated the performance of the proposed wavefront shaping-OCT (WS-OCT) through finite-difference time-domain (FDTD) simulations, demonstrating the exact amplitude and phase profiles of the injected beam within a turbid medium whose scattering properties are similar to those of clinically important human tissues
Summary
Scattering of waves due to inhomogeneous material compositions is a fundamental physical phenomenon on which most imaging methodologies, from seismology to medical imaging, are based. Various solutions proposed so far, including optical clearing method [6,7,8], may be applicable in some situations, but a universal method that can fundamentally reduce multiple scattering-related decoherence without physically altering the sample has yet to be discovered To remedy this situation, wavefront shaping, which has been successfully utilized for various other purposes [9,10,11,12,13,14,15,16,17,18], was recently applied for the first time to OCT [19, 20]. The MCS is a stochastic ray-tracing method based on scattering phase function and, as such, is not suitable for the exact calculation of electromagnetic vector fields necessary for analyzing the new OCT methodology [24] Instead of these existing methods, we adopt finite-difference time-domain (FDTD) analysis [26,27,28,29,30], which is a first-principle based method with very general applicability. The performance of WS-OCT is calculated and compared to that of conventional OCT, including the effect of a finite numerical aperture of real OCT systems
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