Multispectral imaging in the extended near-infrared window based on endogenous chromophores

Abstract

Abstract. To minimize the problem with scattering in deep tissues while increasing the penetration depth, we explored the feasibility of imaging in the relatively unexplored extended near infrared (exNIR) spectral region at 900 to 1400 nm with endogenous chromophores. This region, also known as the second NIR window, is weakly dominated by absorption from water and lipids and is free from other endogenous chromophores with virtually no autofluorescence. To demonstrate the applicability of the exNIR for bioimaging, we analyzed the optical properties of individual components and biological tissues using an InGaAs spectrophotometer and a multispectral InGaAs scanning imager featuring transmission geometry. Based on the differences in spectral properties of tissues, we utilized ratiometric approaches to extract spectral characteristics from the acquired three-dimensional "datacube". The obtained images of an exNIR transmission through a mouse head revealed sufficient details consistent with anatomical structures.

Supercontinuum optimization for dual-soliton based light sources using genetic algorithms in a grid platform

“…1] exhibiting two peaks centered at pre-defined wavelengths. This type of multi-peak spectral illumination is very often required for OCT applications in the NIR II [29] and the simultaneous presence of the two operating spectral components is a prerequisite for real time imaging [33,34]. The two peaks we obtain are the first and second Raman solitons presenting a clean bell-shaped spectral profile, essential for OCT [35], with widths providing a decent longitudinal resolution l c ≈ 10 µm [36].…”

“…3(a) and 3(d), the target spectral channels where chosen from Ref. [29] in order to illustrate the solution for a λ (nm) 3(c,f), demonstrate the tunability of such source, keeping λ c 1 − λ c 2 fixed to 100 nm without replacing the PCF but merely adjusting the input pulse parameters. We checked by benchmarks that several runs of the GA with fixed λ c 1,2 provided systematically very similar optimal results and therefore only one is shown here for each different case.…”

“…To demonstrate the usefulness of this method, we consider in this work the two spectral channels separated by 100 nm (see, e.g., Ref. [29]). The optimization method finds the optimal input pulse parameters, namely central wavelength, λ 0 , temporal width, T 0 , and peak power, P 0 , yielding the desired spectra.…”

“…In the present work, we are interested in OCT applications enabled by fiber based illumination [25,26] in the second near IR window (NIR II) [27][28][29] where λ ∈ [1, 1.4] µm, typically in the anomalous GVD regime of highly nonlinear photonic crystal fibers (PCFs). Because of the typical dispersion landscape, sources in the NIR II window may be based on the bright optical solitons arising during SC generation through the intricate soliton fission effect [30,31].…”

High Throughput AOTF Hyperspectral Imager for Randomly Polarized Light

“…In addition to using a filter wheel with a number of bandpass filters [18], acousto-optic tunable filters (AOTFs) and liquid crystal tunable filters (LCTFs) are commonly used because they can freely select spectral band at high speed (ms/step or faster) and contain no mechanical moving parts [3]. For low frame rate applications where detailed spectral and/or even time-domain information is required, pixel-by-pixel raster scanning with a spectrometer may be used [19]. Recent advances in in-pixel filter technology also led to multispectral imagers with spectral selectivity integrated on-chip or even in-pixel [20,21].…”