Depth‐resolved multimodal imaging: Wavelength modulated spatially offset Raman spectroscopy with optical coherence tomography

Abstract

A major challenge in biophotonics is multimodal imaging to obtain both morphological and molecular information at depth. We demonstrate a hybrid approach integrating optical coherence tomography (OCT) with wavelength modulated spatially offset Raman spectroscopy (WM‐SORS). With depth colocalization obtained from the OCT, we can penetrate 1.2‐mm deep into strong scattering media (lard) to acquire up to a 14‐fold enhancement of a Raman signal from a hidden target (polystyrene) with a spatial offset. Our approach is capable of detecting both Raman and OCT signals for pharmaceutical particles embedded in turbid media and revealing the white matter at depth within a 0.6‐mm thick brain tissue layer. This depth resolved label‐free multimodal approach is a powerful route to analyze complex biomedical samples.

Towards automated cancer screening: Label‐free classification of fixed cell samples using wavelength modulated Raman spectroscopy

“…The use of wavelength modulation in Raman spectroscopy and the resulting removal of autofluorescence provides clear benefits to its ability to automatically classify cells over conventional Raman scattering, without the requirement for manual baseline fitting, additional lasers or optical gates. It is entirely feasible that the technique could be combined with other imaging methods such as optical coherence tomography or digital holographic microscopy in order to provide a cell ‘topography’ map for automated point sampling. It is hoped that such a system could be introduced to clinical settings in order to reduce the burden on manual cytological diagnosis, as well as increasing the likelihood of a correct outcome for patients.…”

Wide-field multiphoton imaging through scattering media without correction

“…Similar to our previous work ( 50 ), rat brain tissue was obtained from adult Sprague Dawley rats, in accordance with the UK Animals (Scientific Procedures) Act 1986. It was fixed and then sectioned into slices at thicknesses of 200 and 400 μm.…”

In-vivo Raman spectroscopy: from basics to applications

“…To address the issue of obtaining both morphological and molecular information at depth, a hybrid approach integrating OCT with wavelength modulated spatially offset Raman spectroscopy (WM-SORS) was introduced. 104 Using polystyrene in lard phantom, coregistered Raman spectroscopy and OCT measurements at depths of up to 1.2 mm were demonstrated. The wavelength modulation additionally suppresses fluorescence background.…”