Extended-focus optical coherence microscopy for high-resolution imaging of the murine brain

Abstract

We propose a new method and optical instrumentation for mouse brain imaging based on extended-focus optical coherence microscopy. This in vivo imaging technique allows the evaluation of the cytoarchitecture at cellular level and the circulation system dynamics in three dimensions. This minimally invasive and non-contact approach is performed without the application of contrasting agents. The optical design achieved a resolution of 2.2 μm over a distance of 800 μm, which was sufficient to obtain a detailed three-dimensional image of a wild-type mouse's brain down to the layer III of the cortex. Intrinsically contrasted microvessels and structures similar to the bodies of neurons were distinguishable.

3D in vivo imaging with extended‐focus optical coherence microscopy

“…At the focal plane, our xf‐OCM had ∼5 dB lower SNR and ∼10 dB higher sidelobe than standard OCM. Although its performance of focus extension was not as good as previous axicon‐based xf‐OCM systems , it gained advantanges of smaller SNR loss and sidelobes, as well as the ease of integrating an annular mask into the imaging system. Our study also showed that this xf‐OCM system was immune to spherical aberrations caused by mismatched refractive indexes of different mediums in the light path.…”

“…As a result, the imaging speed was reduced, which may not be desired in time‐sensitive imaging experiments, such as detecting the blood flow with a phase variance OCM technique . However, in cases of the light source being ultrafast lasers, such as femtosecond lasers, the annular mask is no longer an issue for energy efficiency since these laser sources usually have a broad range of high output power levels . We can easily compensate the loss of light power, caused by the annular mask, through raising the laser power.…”

“…Approximate Bessel beams can be created in both near and far fields after the axicon lens . OCT imaging with axicon lenses is not new and has been well studied . The disadvantage of axicon lens is that it causes strong sidelobe noise and its performance is very sensitive to its alignment to the incident beam .…”

“…OCT imaging with axicon lenses is not new and has been well studied . The disadvantage of axicon lens is that it causes strong sidelobe noise and its performance is very sensitive to its alignment to the incident beam . The other way of producing quasi‐Bessel beams is to manipulate the phase of the input light beam.…”

Design and Implementation Guidelines for a Modular Spectral-Domain Optical Coherence Tomography Scanner

“…A Bessel beam with a spot size similar to a Gaussian beam offers a longer depth of focus [71][72][73]. The compromise here is that Bessel beams have relatively strong side lobes which can affect the accuracy of some OCT measurements.…”