Brain refractive index measured in vivo with high-NA defocus-corrected full-field OCT and consequences for two-photon microscopy

Binding, Jonas; Arous, Juliette Ben; Léger, Jean-François; Gigan, Sylvain; Boccara, Claude; Bourdieu, Laurent

doi:10.1364/oe.19.004833

Cited by 161 publications

(134 citation statements)

References 29 publications

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“…2). In agreement with this observation, the reflection signal may be due to changes in refractive index between the aqueous neural tissue and the lipid-rich myelin [18], analogous to a thin-film interference effect. We used NIR reflectance to perform a large area reconstruction of a slice of hippocampus from a Thy1-GFPM mouse.…”

Section: Resultssupporting

confidence: 69%

Label-free near-infrared reflectance microscopy as a complimentary tool for two-photon fluorescence brain imaging

Mascaro¹,

Costantini²,

Margoni³

et al. 2015

Biomed. Opt. Express

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Abstract:In vivo two-photon imaging combined with targeted fluorescent indicators is currently extensively used for attaining critical insights into brain functionality and structural plasticity. Additional information might be gained from back-scattered photons from the near-infrared (NIR) laser without introducing any exogenous labelling. Here, we describe a complimentary and versatile approach that, by collecting the reflected NIR light, provides structural details on axons and blood vessels in the brain, both in fixed samples and in live animals under a cranial window. Indeed, by combining NIR reflectance and two-photon imaging of a slice of hippocampus from a Thy1-GFPm mouse, we show the presence of randomly oriented axons intermingled with sparsely fluorescent neuronal processes. The back-scattered photons guide the contextualization of the fluorescence structure within brain atlas thanks to the recognition of characteristic hippocampal structures. Interestingly, NIR reflectance microscopy allowed the label-free detection of axonal elongations over the superficial layers of mouse cortex under a cranial window in vivo. Finally, blood flow can be measured in live preparations, thus validating label free NIR reflectance as a tool for monitoring hemodynamic fluctuations. The prospective versatility of this label-free technique complimentary to twophoton fluorescence microscopy is demonstrated in a mouse model of photothrombotic stroke in which the axonal degeneration and blood flow remodeling can be investigated.

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Section: Resultssupporting

confidence: 69%

Label-free near-infrared reflectance microscopy as a complimentary tool for two-photon fluorescence brain imaging

Mascaro¹,

Costantini²,

Margoni³

et al. 2015

Biomed. Opt. Express

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“…One disadvantage of our current fOCT system is that the recording took about 4-4.5 hours at a rate of 0.5 volumes/sec because of the limitation from the speed of PC data transfer (memory). We thought there is a possibility to increase system speed by introducing high-speed memory and parallel signal computing technologies such as GPU or FPGA to the current system [36,37]. At this stage, fOCT signal in GL was detected.…”

Section: Discussionmentioning

confidence: 99%

“…2(e), and it corresponded to 2.1 mm (2.9 mm in air) × 2.0 mm × 1.0 mm, respectively. The refractive index of the brain tissue was assumed to be 1.38 [36]. The voxel size corresponded to 5.25 μm (z-axis) × 10 μm (xaxis) × 20 μm (y-axis).…”

Section: Data Acquisition and Processing Of Octmentioning

confidence: 99%

Functional optical coherence tomography of rat olfactory bulb with periodic odor stimulation

Watanabe¹,

Rajagopalan²,

Nakamichi³

et al. 2016

Biomed. Opt. Express

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Abstract:In rodent olfactory bulb (OB), optical intrinsic signal imaging (OISI) is commonly used to investigate functional maps to odorant stimulations. However, in such studies, the spatial resolution in depth direction (z-axis) is lost because of the integration of light from different depths. To solve this problem, we propose functional optical coherence tomography (fOCT) with periodic stimulation and continuous recording. In fOCT experiments of in vivo rat OB, propionic acid and m-cresol were used as odor stimulus presentations. Such a periodic stimulation enabled us to detect the specific odorresponses from highly scattering brain tissue. Swept source OCT operating at a wavelength of 1334 nm and a frequency of 20 kHz, was employed with theoretical depth and lateral resolutions of 6.7 μm and 15.4 μm, respectively. We succeeded in visualizing 2D cross sectional fOCT map across the neural layer structure of OCT in vivo. The detected fOCT signals corresponded to a few glomeruli of the medial and lateral parts of dorsal OB. We also obtained 3D fOCT maps, which upon integration across z-axis agreed well with OISI results. We expect such an approach to open a window for investigating and possibly addressing toward inter/intra-layer connections at high resolutions in the future. 181-192 (1997). 33. Y. Nakamichi, V. A. Kalatsky, H. Watanabe, U. M. Rajagopalan, and M. Tanifuji, "3D structure of the orientation column in cat primary cortex revealed by functional optical coherence tomography," Abstr. Soc. Neurosci. 270. 01 (2011), http://www.abstractsonline.com/Plan/ViewAbstract.aspx?sKey=d023089b-a64b-4aa9-b3cb-6129bde54e45&cKey=09b7566c-c153-4692-8113-1a04e1af0b1d&mKey=%7b8334BE29-8911-4991-8C31- 3067-3086 (2012).

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“…[17][18][19][20][21] However, these methods have their limitations to be applied to the RI distribution of AC, such as the large amount of sample consumption or the difficulty to determine the RI within a small spot. The only previous work about the depth-dependent RI distribution of AC was based on an optical coherent tomography (OCT).…”

Section: Introductionmentioning

confidence: 99%

Depth-dependent refractive index of normal and early degenerated articular cartilage

Wang¹,

Wu²,

Kirk³

2013

J. Biomed. Opt

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Abstract. The depth distributions of refractive index (RI) in normal and early degenerated articular cartilage (AC) were measured and correlated to the pathological statuses. Utilizing a confocal microscope, the depth distribution of RI was determined with an interval of 50 μm from the articular surface and approximated as a smooth curve. The fluctuation of RI was quantified with a specially defined coefficient and the proteoglycan (PG) loss was quantified with histological images. The overall RI of the AC collected from the femoral condyles of mature sheep was 1.4444. Significant differences existed in the refractive indices of different cartilage samples or even in the different depths of the same sample. The RI of normal cartilage distributed as a regular ramp or arch curve with depth and peaked in the middle-deep zone. The cartilage samples detected with high PG losses were coupled with severe fluctuations of RI. The fluctuating level was increased with pathological progress. The coefficient of RI fluctuation can distinguish the normal cartilage from the initially degenerated one, which potentially provides an indicator to detect the pathological development of AC. © The Authors. Published by SPIE under a Creative Commons Attribution 3.0 Unported License. Distribution or reproduction of this work in whole or in part requires full attribution of the original publication, including its DOI.

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Brain refractive index measured in vivo with high-NA defocus-corrected full-field OCT and consequences for two-photon microscopy

Cited by 161 publications

References 29 publications

Label-free near-infrared reflectance microscopy as a complimentary tool for two-photon fluorescence brain imaging

Label-free near-infrared reflectance microscopy as a complimentary tool for two-photon fluorescence brain imaging

Functional optical coherence tomography of rat olfactory bulb with periodic odor stimulation

Depth-dependent refractive index of normal and early degenerated articular cartilage

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