Deep imaging with 1.3 µm dual-axis optical coherence tomography and an enhanced depth of focus

Abstract

For many clinical applications, such as dermatology, optical coherence tomography (OCT) suffers from limited penetration depth due primarily to the highly scattering nature of biological tissues. Here, we present a novel implementation of dual-axis optical coherence tomography (DA-OCT) that offers improved depth penetration in skin imaging at 1.3 µm compared to conventional OCT. Several unique aspects of DA-OCT are examined here, including the requirements for scattering properties to realize the improvement and the limited depth of focus (DOF) inherent to the technique. To overcome this limitation, our approach uses a tunable lens to coordinate focal plane selection with image acquisition to create an enhanced DOF for DA-OCT. This improvement in penetration depth is quantified experimentally against conventional on-axis OCT using tissue phantoms and mouse skin. The results presented here suggest the potential use of DA-OCT in situations where a high degree of scattering limits depth penetration in OCT imaging.

Spatially offset optical coherence tomography: Leveraging multiple scattering for high-contrast imaging at depth in turbid media

“…Because of the simple geometry used in SO-OCT, this technique can be easily combined with other approaches, such as adaptive optics ( 34 ) and beam shaping ( 16 , 35 , 36 ), in order for the illumination light to penetrate into turbid samples deeper. While this study investigated imaging at 800 and 1300 nm, we expect that the use of even longer wavelengths would also have improved imaging depth with SO-OCT ( 37 ).…”

“…For instance, adaptive optics approaches to correcting wavefront aberrations using a spatial light modulator have increased the depth obtained ( 12 , 13 ). Alternatively, a dual-axis geometry with overlapping beams has been developed to reduce multiple scattering in both confocal microscopy ( 14 ) and dual-axis OCT ( 15 , 16 ). Dark-field approaches, including in OCT ( 17 ), have also been used to reject extraneous background noise, such as from reflective imaging interfaces.…”

“…In most practical settings, the high flux from surface-scattered photons will obscure depth information within the detector noise before the fundamental limit in SMR is reached. Previous demonstrations in extending depth penetration through the reduction of multiple scattering have shown the identification of highly reflective or scattering samples below aberrating media ( 12 , 16 , 19 ). However, their utility in the practical cases of uniformly scattering biological tissue is yet to be determined.…”

The application of artificial intelligence in the detection of basal cell carcinoma: A systematic review

“…20 OCT acquires real-time cross-sectional images of the skin with a penetration depth of approximately 1.0-1.5 mm and a <7.5 μm lateral and <5 μm axial optical resolution (Figure 1b), although new techniques may increase penetration depth. 21 Based on the reflections, architectural details of lesions and tissues can be visualized enabling the identification of a lesion as BCC and its respective subtype (superficial, nodular or infiltrative). Hussain et al 22 established a set of morphological features such as a honeycomb-like structure, disruption of the dermal-epidermal junction, hypo reflective lateral border and dilated vasculature.…”

“…The core concept of OCT is similar to ultrasound imaging as it measures the echo delay and intensity produced by a reflected signal, in this case infrared light instead of sound 20 . OCT acquires real‐time cross‐sectional images of the skin with a penetration depth of approximately 1.0–1.5 mm and a <7.5 μm lateral and <5 μm axial optical resolution (Figure 1b), although new techniques may increase penetration depth 21 …”