Three-dimensional Analysis of Cerebral Microvessels and Nerve Cells with Optical Coherence Tomography

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This research project was aimed to analyze 3-dimensional configuration of microvessels and nervous tissue in the cerebral cortex using optical coherence tomography (OCT) system, which is especially designed for in vivo imaging of biological tissues in our laboratory, and to clarify temporal and spatial coupling between neuronal activity and microcirculatory function.In the OCT system, superluminescent diodes (SLD) with central wavelength of 813 and 940 nm were used for low-coherence light source. The spatial resolutions of the system was evaluated by in vitro and in vivo measurements to be 16x14 and 8x17 μm^2 (longitudinal (depth) x lateral directions) for 813 and 940 nm, respectively. The penetration depth of the OCT system was 0.7-1 mm for the rat cerebral cortex.The OCT observation revealed that dura and without dura. The responses of the somatosensory cortices during electrical stimulation of the hind paw were also different among the preparation methods ; Delayed swelling of the cortical surface appeared in the somatosensory cortex following the stimulation in the case of dura removal, which was restricted to a thin surface layer with less than several 10 μm. It is considered to reflect the reactive hyperemia accompanying the neuronal activation.Analyzing Doppler frequency shift due to the blood flow in microvessels by the use of a short time Fourier transform (STFT), cross-sectional velocity profiles and their temporal changes were measured for the rat pial microvessels. While the central velocity in the pial arterioles varied largely with time following the heart beats, the velocity profiles nearly exhibited Poiseuille distribution. These results are consistent with theoretical prediction for the blood flow in microvessels with small Reynold's number and small Womersley parameter. The results of this study indicate that the OCT may provide 3-dimensional information of blood flow distribution in the cerebral cortex with high temporal resolution