Brain imaging with extended-focus optical coherence tomography at different scales and spectral ranges (Conference Presentation)

Over the past decades, optical coherence tomography has emerged as an important imaging technique to study biological processes through its ability to perform three-dimensional imaging at high acquisition rates and non-invasively. Furthermore, OCT has shown a growing interest in brain imaging through its capacity in obtaining functional information such as cellular viability, hematocrit and blood flow velocity. Although OCT can reach image depths spanning a few millimeters, the effective imaging depth is typically dictated by the depth-of-field of the imaging optics. In traditional OCT systems, this depth-of-field is given by the Rayleigh range and is thus coupled to the lateral resolution. As such, increasing the numerical aperture of the system reduces the imaging depth, ultimately hampering the depth-multiplexing advantage of OCT. Wavefront engineering schemes have been devised to overcome this limitation, providing the OCT systems with an extended-focus. We present here two extended-focus OCT systems (xf-OCT) optimized for cerebral imaging. The first system operates in the visible wavelength range and is designed to image the superficial cortex of mice at high contrast and at high resolution. Its high axial and lateral resolution of 0.8 and 1.4 um respectively, maintained over 200 um enable resolving structures such as myelinated axons, neuronal cells and micro-vessels in vivo. The second system is optimized for deep microvascular cortical imaging and operates in the infrared spectral range. Through its extended-focus and increased penetration, the second system can provide maps of cortical microvasculature over 800 um in depth in the cortex in vivo.