Feature Of The Week 03/31/2019: Depth resolved label-free multimodal optical imaging platform to study morpho-molecular composition of tissue
We have developed a multimodal laser scanning microscope (LSM) platform combining optical coherence tomography (OCT), spectral focusing coherent anti-Stokes Raman scattering (SF-CARS), second harmonic generation (SHG) and two-photon excited fluorescence (TPF). Morphological, molecular and biochemical information from tissues can be collected in a non-invasive and label-free manner by merging ultra-fast Ti:sapphire lasers with well-developed optical imaging techniques. The combination of the proposed imaging modalities enables increased sensitivity and specificity for detection of early tissue alteration related to pathological condition and may offer novel insights in the diagnosis of diseases.
OCT is fused with nonlinear optical microscopy techniques to perform wide-field OCT scanning first and consecutively simultaneous nonlinear optical imaging (NLOI) in the backward propagation direction without interference of one modality with the others and by that compromising image quality. This approach provides fast structural ultrahigh resolution wide-field pre-screening to localize specific areas of interest in tissue and highly contrasted images by zooming into the cellular level to obtain specific information about morphology, function and metabolism of biological tissue in a non-invasive and non-destructive endogenous manner without the need to stain the tissue for contrast enhancement. The specimen is completely undisturbed from dye or photo-bleaching.
OCT supports deeper tissue interrogation for in situ cell-based imaging studies than standard microscopy techniques and a big picture can generated. Suspicious and interesting regions can be identified and correlated with endogenous molecular biomarkers obtained from NLOI. The interpretation of the images can be performed instantaneously. OCT is used as volumetric “GPS” to identify lesions of interest within the tissue, SF-CARS provides chemical selectivity via Raman mode resolution, i.e. to visualize lipid and protein distribution, SHG offers information about non-centrosymmetric structure, i.e. collagen with the tissue and TPF images endogenous sub-cellular fluorophores to provide biochemical changes within the tissue, i.e. elastin composing extracellular matrix. Additionally a spectral dimension is added to the images by means of SF-CARS and Raman tuning between 2800 and 3100 wavenumbers making the spectral discrimination easier and more accurate. The potential of the platform to obtain complementary structural and functional information within tissue and cells is demonstrated in an established animal model by integrating SF-CARS, SHG and TPF into a LSM and adding OCT. Our proposed system can be interfaced into commercial LSM systems due to its modular concept.
We believe that our platform can potentially address a wide variety of unmet clinical needs for disease detection and localization down to the cellular level by providing a fast, highly sensitive and specific method with a wealth of intrinsic molecular and morphological information.
For more information see recent Article. Courtesy Angelika Unterhuber from Medical University of Vienna.