Phase-stable swept source OCT angiography in human skin using an akinetic source

Abstract

Abstract:We demonstrate noninvasive structural and microvascular contrast imaging of human skin in vivo, using phase difference swept source OCT angiography (pOCTA). The pOCTA system employs an akinetic, all-semiconductor, highly phase-stable swept laser source which operates at 1340 nm central wavelength, with 37 nm bandwidth (at 0 dB region) and 200 kHz A-scan rate. The phase sensitive detection does not need any external phase stabilizing implementations, due to the outstanding high phase linearity and sweep phase repeatability within 2 mrad. We compare the performance of phase based OCTA to speckle based OCTA for visualizing human vascular networks. pOCTA shows better contrast especially for deeper vascular details as compared to speckle based OCTA. The phase stability of the akinetic source allows the OCTA system to show decent vascular contrast only with 2 B-scans. We compare the performance of using 2 versus 4 B-scans for calculating the vascular contrast. Finally, the performance of a 100 nm bandwidth akinetic laser at 1310 nm is investigated for both OCT and OCTA.

Combined multi-modal photoacoustic tomography, optical coherence tomography (OCT) and OCT angiography system with an articulated probe for in vivo human skin structure and vasculature imaging

“…Knowing that most OCT dermatological research uses 1300 nm band for its good compromise between penetration depth and resolution [12], we designed a switchable sensor head for our dual modality PAT/OCT system so that the FPI sensor is only in place during PAT scan, while in the succeeding OCT scan another sensor head is placed to circumvent the passband limit and to avoid possible sensitivity drop from the FPI. With this switchable sensor head, we incorporated our latest phase stable SS-OCT angiography system featuring an akinetic source at 1340 nm [20] into the all optical PAT system. A probe for these two modalities is manufactured to be mounted on an articulated arm made from a boom stand (V7 Articulating Boom Stand, Omano Microscopes, China).…”

“…Volume rendering and animation are achieved using ImageJ [21] and Amira (FEI, France). As for a more detailed description of the working principles of all optical PAT and akinetic SS-OCT as well as the algorithms used for image reconstruction and enhancement, the readers are referred to [12,22,23] and [20], respectively.…”

Highly phase-stable 200 kHz swept-source optical coherence tomography based on KTN electro-optic deflector

“…Various techniques such as speckle variance imaging [34], phase variance imaging [39], temporal frequency analysis [34], and averaged phase difference imaging [11], were used in the study to provide additional functional contrasts. We followed the algorithms detailed in aforementioned literatures and implemented the algorithms in MATLAB R2016a.…”

“…The structural information provided by OCT is sometimes insufficient for a comprehensive understanding of biological samples, and extra functional contrast capabilities such as phase contrast are often sought. For example, in OCT angiography (OCTA), the phase change between consecutive A-lines could be used to obtain the Doppler frequency shift resulted from the blood flow, and thus the blood flow rate [10,11]. In optical coherence elastography (OCE), the phase change of the sample induced by external mechanical stimulus is recorded and analyzed to obtain its mechanical properties [12][13][14].…”

Regression-based algorithm for bulk motion subtraction in optical coherence tomography angiography

“…It has become an important clinical tool in ophthalmology [6][7][8][9][10][11][12][13][14] and exhibits great potential for dermatology [15,16] and neurology [17]. To obtain flow signal, OCTA algorithms [1,3,[18][19][20] rely on mathematical operations that quantify variations in the amplitude and/or the phase of optical coherence tomography (OCT) signal between at least two consecutive B-scans acquired at the same raster position.…”