High-spatial-resolution deep tissue imaging with spectral-domain optical coherence microscopy in the 1700-nm spectral band

Abstract

We present three-dimensional (3-D) highresolution spectral-domain optical coherence microscopy (SD-OCM) by using a supercontinuum (SC) fiber laser source with 300-nm spectral bandwidth (full-width at halfmaximum) in the 1700-nm spectral band. By using lowcoherence interferometry with SC light and a confocal detection scheme, we realized lateral and axial resolutions of 3.4 and 3.8 μm in tissue (n ¼ 1.38), respectively. This is, to the best of our knowledge, the highest 3-D spatial resolution reported among those of Fourier-domain optical coherence imaging techniques in the 1700-nm spectral band. In our SD-OCM, to enhance the imaging depth, a full-range method was implemented, which suppressed the formation of a coherent ghost image and allowed us to set the zero-delay position inside the samples. We demonstrated the 3-D high-resolution imaging capability of 1700-nm SD-OCM through the measurement of an interference signal from a mirror surface and imaging of a single 200-nm polystyrene bead and a pig thyroid gland. Deep tissue imaging at a depth of up to 1.8 mm was also demonstrated. This is the first demonstration of 3-D high-resolution SD-OCM in the 1700-nm spectral band.

Signal-to-background ratio and lateral resolution in deep tissue imaging by optical coherence microscopy in the 1700 nm spectral band

“…Finally, we demonstrated high-contrast deep tissue imaging of a mouse brain. For this experiment, we used a full-range high-resolution 1700 nm SD-OCM system using an SC fiber laser source with a 300 nm spectral band (full width at half maximum) 19 . For this OCM system, we used another custom-built spectrometer consisting of a 150 lines/mm blazed diffraction grating (015–200, Shimadzu) and two achromatic lenses (AC508-040-C and AC508-050-C, Thorlabs) 14 .…”

“…However, the penetration depth of the 1700-nm TD-OCM was limited to around 1 mm due to the relatively low signal sensitivity (93 dB). Recently, we developed 1700 nm spectral domain (SD) OCM with full range method to enhance the penetration depth, and the improved signal sensitivity (100 dB) enabled us to realize high-resolution deep tissue OCM imaging of pig thyroid glands with a penetration depth of 1.8 mm 19 .…”

“…The reduction of the confocal gating effect degrades the lateral resolution of OCM and this degradation of the lateral resolution would be much more severe in OCM compared with OCT, which is based on imaging systems with low confocal gating effects. Although we have recently developed high-resolution TD and SD-OCM in the 1700 nm spectral band as mentioned above 18,19 , quantitative study of the imaging quality in deep tissue imaging (especially at a depth beyond 1 mm) has not performed yet.…”

Biomimicking Atherosclerotic Vessels: A Relevant and (Yet) Sub-Explored Topic

“…It is widely used in medicine, specifically in dermatology [ 64 ], ophthalmology [ 65 ], and cardiology [ 66 ]. Particularly, in intravascular OCT, a catheter comprising an optical fiber transmits the light and measures the “echoes” of light backscattered by the sample to build an image while it is rotated and pulled across the length of the assessed artery [ 67 ]. Therefore, it can distinguish atherosclerotic plaque structures based on grey-scale images.…”

Imaging of the skin microvascularization using spatially depolarized dynamic speckle

“…It benefits from a spatial resolution on the order of few microns and is typically limited to submillimeter penetration depth 16 , 17 due to the inherent use of a wide optical spectrum inside which some wavelengths have reduced penetration depths. Recently, using an optical spectrum shifted to the infrared region, 18 penetration depth was increased by roughly 1 mm, but spatial resolution appears to decrease rapidly with depths greater than 1 mm. OCT has broadened its application field to the imaging of blood vessels.…”