Knowledge of myocardial fiber architecture is essential towards understanding heart functions. We demonstrated in this study a method to map cardiac muscle structure using the local optical axis obtained from polarization-sensitive optical coherence tomography (PSOCT). An algorithm was developed to extract the true local depth-resolved optical axis, retardance, and diattenuation from conventional round-trip results obtained in a Jones matrix-based PSOCT system. This method was applied to image the myocardial fiber orientation in a bovine heart muscle sample.

We proposed a method to extract depth-resolved local retardance in birefringent samples from conventional polarization-sensitive optical coherence tomography (PSOCT) that uses one circularly polarized incident light. Despite the wide use of such PSOCT systems in characterizing birefringent samples, the measured cumulative retardance does not represent the true cumulative retardance when optical axis varies with depth. A Jones calculus based algorithm was designed to derive the local depth-resolved retardance from conventional cumulative PSOCT results. The algorithm was tested in samples with homogeneous optical axis as well as samples with depth-dependent optical axis.

Abstract. An algorithm was developed to obtain depthresolved local optical axis in birefringent samples by using conventional polarization-sensitive optical coherence tomography (PSOCT) that uses a single circularly polarized incident light. The round-trip sample Jones matrices were first constructed from the cumulative PSOCT results. An iterative method was then applied to construct the depth-resolved local Jones matrix from which the local optical axis was calculated. The proposed algorithm was validated in samples with homogeneous axis and with depth-varying optical axis. Imaging examples were shown to demonstrate the capability of this method for extracting correct local axis and revealing features not evident in other images.

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We present a spectral domain polarization sensitive optical coherence tomography (PSOCT) system that incorporates: 1) a spectrometer configured with a single line-scan camera for spectral interferogram detection, 2) a reference delay line assembly that provides a fixed optical pathlength delay between the lights of two orthogonal polarization states, and 3) a moving reference mirror that introduces a constant modulation frequency in the spatial spectral interferograms while the probe beam is scanned over the sample. The system utilizes the full range of complex Fourier plane for polarization sensitive imaging, where OCT images formed by the vertical and horizontal polarization beam components appear adjacent to each other. It is able to provide imaging of retardation, fast optic axis and backscattered intensity of the interrogated biological tissue. The system is experimentally demonstrated both in vitro and in vivo with an imaging rate at 10,000 A scans per second.

Abstract:We report a simple implementation to acquire spectral domain polarization-sensitive optical coherence tomography (PSOCT) using a single camera. By combining a dual-delay assembly in the reference arm and offset B-scan in the sample arm, the orthogonal vertical-and horizontalpolarized images were acquired in parallel and spatially separated by a fixed distance in the full range image space. The two orthogonal polarization images were recombined to calculate the intensity, retardance and fast-axis images. This system was easy to implement and capable of acquiring highspeed in vivo 3D polarization-sensitive OCT images.

Optical diffuse reflectance in fibrous tissues depends on measurement angles in relation to fiber orientation. In this study, path-length resolved optical reflectance was measured in tendon and skeletal muscle samples using a low-coherence Mach-Zehnder interferometer. The results show that the angular dependency in reflectance was eliminated in tendon tissue when representing reflectance as a function of mean path-length. Our analysis indicated that this observation can be understood in the frame work of anisotropic diffuse theory. However the same phenomenon was not observed in muscles, suggesting involvement of additional scattering mechanisms.

In this study, an optical coherence tomography (OCT) system is implemented for the noninvasive characterization of photothermolysis in human skin induced by ablative fractional lasers (AFLs) and non-ablative fractional lasers (NAFLs). With OCT imaging, microthermal zones (MTZs) induced by fractional lasers can be noninvasively visualized, and the size of induced MTZs can be quantitatively evaluated. According to the OCT results, the center region of the induced MTZ corresponds to weaker backscattered intensity after the AFL exposure as a result of tissue volatilization by photon energy. In contrast, after the NAFL exposure, the skin tissue is damaged and coagulated but not volatilized, which causes the backscattered intensity of the induced MTZ enhanced in the OCT image. To further identify the photothermolysis induced by AFLs or NAFLs, the backscattered intensities of MTZs are compared with those of the untreated tissue from the OCT results. The statistical result shows a clear difference in scattering properties of photothermolysis induced by AFLs and NAFLs. Finally, the induced photodamage at various depths can also be quantitatively evaluated, enabling an investigation of the relationship between the photodamage and the depth.