Human Brain Imaging by Optical Coherence Tomography

Human Brain Imaging by Optical Coherence Tomography◾ 401 the sections onto glass slides, which are dried, histologically stained, and coverslipped for preservation. This process is likely to introduce irremediable distortions at almost every step. Some of the distortions and artifacts from histology are demonstrated in Section 18.5. 4 Advantages and Limitations. Full 3D reconstruction of the human brain from histological sections (stained for intact neurons) has been published by Amunts et al.(2013). Manual and automatic repairs on the damaged slices were performed as well as non-linear registration of the coronal slices to the MRI to reconstruct the entire volume. Even after this labor-intensive work, the BigBrain still has registration artifacts that are apparent in the other orientations (sagittal and axial). Registration between histology slices is difficult (Arsigny et al., 2005), even with the aid of intermediary images of the undistorted tissue, such as the blockface images or the MRI (Osechinskiy and Kruggel, 2010). Those distortions at the microscopic level can be avoided by imaging the blockface directly, prior to cutting (Odgaard et al., 1990). In contrast to histology, OCT probes the superficial part of a tissue block (a few hundred microns to a millimeter in depth depending on the tissue and the fixation), prior to any sectioning. Thus, OCT can be used to reconstruct brain samples of several cubic centimeters without distortion and with contrasts comparable to histology, as will be shown in the following sections, facilitating the reconstruction of a micron-resolution volume.In this chapter, the principles and basis of Optical Coherence Tomography are first …