Visible spectrum extended-focus optical coherence microscopy for label-free sub-cellular tomography

Abstract

Abstract:We present a novel extended-focus optical coherence microscope (OCM) attaining 0.7 µm axial and 0.4 µm lateral resolution maintained over a depth of 40 µm, while preserving the advantages of Fourier domain OCM. Our system uses an ultra-broad spectrum from a supercontinuum laser source. As the spectrum spans from near-infrared to visible wavelengths (240 nm in bandwidth), we call the system visOCM. The combination of such a broad spectrum with a high-NA objective creates an almost isotropic 3D submicron resolution. We analyze the imaging performance of visOCM on microbead samples and demonstrate its image quality on cell cultures and ex-vivo brain tissue of both healthy and alzheimeric mice. In addition to neuronal cell bodies, fibers and plaques, visOCM imaging of brain tissue reveals fine vascular structures and sub-cellular features through its high spatial resolution. Sub-cellular structures were also observed in live cells and were further revealed through a protocol traditionally used for OCT angiography.

Retinal analysis of a mouse model of Alzheimer’s disease with multicontrast optical coherence tomography

“…Functional extensions of OCT have made it possible to not only visualize contrasts based on backscattered intensity (reflectivity), but also motion (OCTA) [48][49][50] and polarization properties (PS-OCT) such as birefringence. [51][52][53][54] The birefringence of Aβ plaques has been studied in detail using polarimetry, [55][56][57][58] and also with PS-OCT. 59,60 The plaques appear as hyper-scattering structures in standard reflectivity OCT images, [61][62][63] but the addition of polarization-sensitive detection provides an additional tissue-specific contrast. Furthermore, the combination of PS-OCT with OCTA allows a simultaneous analysis of this tissue-specific contrast and changes in the retinal vasculature.…”

Comparison of Intensity- and Polarization-based Contrast in Amyloid-beta Plaques as Observed by Optical Coherence Tomography

“…PS-OCT visualizes amyloid-beta plaques based on their optical scattering and birefringent properties [33][34][35][36]. Previous studies mainly exploited the hyperscattering characteristics of plaques and only one report investigated the birefringent characteristics of neuritic plaques using PS-OCT [19].…”

“…Several recent reports have demonstrated that amyloid-beta plaques in both human and mouse brain tissue can be visualized using either conventional OCT, PS-OCT [19,[32][33][34][35][36] or other functional extensions such as spectroscopic OCT [32] or directional OCT [36]. Label-free imaging of cerebral amyloid-beta plaques has been achieved using extended-focus optical coherence microscopy (OCM) in the near infrared range at 800 nm [34].…”

“…Label-free imaging of cerebral amyloid-beta plaques has been achieved using extended-focus optical coherence microscopy (OCM) in the near infrared range at 800 nm [34]. By shifting to the visible spectrum to achieve sub-micrometer axial resolution, extended-focus OCM has been used to investigate plaques and small fiber tracts in ex-vivo cerebral mouse tissue [35]. A PS-OCM setup in the near infrared around 800 nm enabled the visualization of neuritic amyloid-beta plaques in brain tissue of human AD patients.…”

Visible light optical coherence microscopy of the brain with isotropic femtoliter resolution in vivo

“…With few exceptions [10–12], conventional flying-spot OCT and OCM systems use a symmetric confocal imaging geometry, where the detection path retraces the illumination path, resulting in identical illumination and detection point spread functions (PSFs). While such a configuration facilitates optical alignment, this strategy has disadvantages.…”