High-resolution optical imaging is accompanied by a limited depth of field, making it challenging to obtain non-stitched, high-resolution images of samples with uneven surfaces without performing Z-axis scanning. To solve this problem, we introduced diffractive optical elements into the conventional OCT system and develop a needle-shaped beam OCT system with both long DOF and high resolution, which maintains 8μm lateral resolution over a depth range of 620μm. The system was then employed to perform a 10-day cortical blood perfusion observation after stroke, providing visual and mechanistic insight into stroke, deepening our understanding of the brain response after stroke.
Optical coherence tomography (OCT) has become a promising tool for studying anatomical and functional dynamics of the cerebral cortex, offering advantages such as label-free imaging, high resolution, and non-invasive optical biopsy. However, observing the brains of non-anesthetized and freely moving mice has been a long-standing challenge for OCT. In this study, we designed a wearable OCT probe to observe the vascular morphology of the mouse brain and track short-term vascular changes after thrombosis. We utilized a microelectromechanical system (MEMS) scanning mirror for three-dimensional scanning. Compared to traditional OCT systems, this wearable imaging probe features miniaturization, low cost, portability, and stability, allowing for imaging of the mouse brain in a non-anesthetized and freely moving state. The entire probe weighs 8 g and achieves a lateral resolution of 5.5 μm, a longitudinal resolution of 12 μm, and an effective imaging area of 4 mm × 4 mm. We evaluated the performance of the probe through phantom experiments and imaging of the mouse brain's vascular network, and successfully monitored local vascular morphological changes in the mouse brain shortly after stroke under awake conditions. We believe that the wearable probe can be applied in various fields such as ophthalmology, dermatology, and dentistry, and due to its portability and non-invasiveness, the wearable OCT probe is expected to have wide clinical research applications.
Optical coherence tomography angiography (OCTA) has emerged as a highly competitive technique for visualizing blood perfusion without the need for exogenous contrast agents. However, for high-resolution optical imaging, a tight optical focus is usually needed to achieve the diffraction-limited resolution in optical microscopy, which results in a limited depth of field (DOF), making it challenging to obtain large-scale, non-stitched, high-resolution images of samples with uneven surfaces without performing Z-axis scanning. To solve this problem, we introduce the diffractive optical elements (DOEs) into the conventional Gaussian beam (GB) OCT system and develop a needle-shaped beam (NB) OCT system with both long DOF and high resolution, which maintains 8 μm lateral resolution over a depth range of 620 μm, allowing real-time, non-stitched, large-field imaging of samples with uneven surfaces. OCTA imaging of mouse brains with natural curvature was demonstrated in our work.
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