In vivo high-resolution cortical imaging with extended-focus optical coherence microscopy in the visible-NIR wavelength range.

Arno Bouwens,Daniel Szlag,Paul J Marchand,Theo Lasser

doi:10.1117/1.jbo.23.3.036012

Abstract

Visible light optical coherence tomography has shown great interest in recent years for spectroscopic and high-resolution retinal and cerebral imaging. Here, we present an extended-focus optical coherence microscopy system operating from the visible to the near-infrared wavelength range for high axial and lateral resolution imaging of cortical structures in vivo. The system exploits an ultrabroad illumination spectrum centered in the visible wavelength range (λc = 650 nm, Δλ ∼ 250 nm) offering a submicron axial resolution (∼0.85 μm in water) and an extended-focus configuration providing a high lateral resolution of ∼1.4 μm maintained over ∼150 μm in depth in water. The system's axial and lateral resolution are first characterized using phantoms, and its imaging performance is then demonstrated by imaging the vasculature, myelinated axons, and neuronal cells in the first layers of the somatosensory cortex of mice in vivo.

Highlights

Optical coherence tomography (OCT)[1] has emerged in the past decade as a valuable tool to study cerebral physiology,[2,3,4,5,6] through its ability to perform three-dimensional (3-D) imaging of tissue and vasculature at very high acquisition rates, with A-scan rates typically ranging from 10 to 100 kHz
Most OCT systems operate in the infrared spectral range to maximize the penetration depth in tissue, recent studies have exploited a visible light source to benefit from the characteristic spectral signatures of certain endo- and exogeneous agents at shorter wavelengths.[7,8]
Shifting the central wavelength enables increasing the axial resolution of OCT systems as it is determined by δz ∝ λ2c∕Δλ, where λc is the central wavelength of the source and Δλ is its bandwidth

Summary

Introduction

Optical coherence tomography (OCT)[1] has emerged in the past decade as a valuable tool to study cerebral physiology,[2,3,4,5,6] through its ability to perform three-dimensional (3-D) imaging of tissue and vasculature at very high acquisition rates, with A-scan rates typically ranging from 10 to 100 kHz. Increasing the lateral resolution in conventional OCT systems reduces the depth-of-field (DOF) by restricting the confocal gating and effectively hampering the multiplexing advantage of Fourier domain OCT. Optical coherence microscopy[18] (OCM), the high-NA version of OCT, might require an additional scan in depth to obtain 3-D images.[19,20] This effect can be mitigated by splitting the illumination and detection modes of the OCM system and by illuminating the

Methods

Mouse Preparation

Results

In Vivo Imaging of Cortical Structures

Conclusion and Discussion