Towards ultra-high resolution fibre tract mapping of the human brain - registration of polarised light images and reorientation of fibre vectors

Abstract

Polarised light imaging (PLI) utilises the birefringence of the myelin sheaths in order to visualise the orientation of nerve fibres in microtome sections of adult human post-mortem brains at ultra-high spatial resolution. The preparation of post-mortem brains for PLI involves fixation, freezing and cutting into 100-μm-thick sections. Hence, geometrical distortions of histological sections are inevitable and have to be removed for 3D reconstruction and subsequent fibre tracking. We here present a processing pipeline for 3D reconstruction of these sections using PLI derived multimodal images of post-mortem brains. Blockface images of the brains were obtained during cutting; they serve as reference data for alignment and elimination of distortion artefacts. In addition to the spatial image transformation, fibre orientation vectors were reoriented using the transformation fields, which consider both affine and subsequent non-linear registration. The application of this registration and reorientation approach results in a smooth fibre vector field, which reflects brain morphology. PLI combined with 3D reconstruction and fibre tracking is a powerful tool for human brain mapping. It can also serve as an independent method for evaluating in vivo fibre tractography.

Enhanced characterization of the zebrafish brain as revealed by super-resolution track-density imaging

“…By carefully collecting a series of sections and calculating fiber orientation maps, whole brain fiber tracking can be performed and compared with DWI data. Furthermore, as birefringence data is collected from histological data, the acquired resolution is very high with voxel sizes as small as 100μm 3 in the human brain (Palm et al 2010). This voxel size is directly comparable to that achieved in human TDI data , and could potentially be used to validate the DEC stTDI technique.…”

“…For example, our histological sections demonstrate the location of neurons and fiber tracts but do not contain directional information. However, a new tractography technique, three-dimensional polarized light imaging (3D-PLI) has been recently developed that can visualize the orientation of nerve fibers based upon their birefringence (Axer et al 2011;Palm et al 2010). Birefringence, is the product of the arrangement of proteins and lipids in myelin, and has an optical anisotropy that reflects the spatial fiber architecture of nerve fibers.…”

How Klingler’s dissection permits exploration of brain structural connectivity? An electron microscopy study of human white matter

“…For obvious ethical reasons, only the three methods described below are currently used as anatomical validation tools of MR tractography. First, polarized light imaging (PLI) records light transmission through an anatomical slice; due to optical birefringence of the myelin sheaths, light transmission depends on the relative orientations of white matter fibers and informs on their organization (Dammers et al 2010;Palm et al 2010). Refinements of this promising technique enable fiber direction to be evaluated at a micrometer-scale resolution, but it has the same limitation as histological preparation for axonal tracing, i.e., loss of 3D coherence of fiber tracts due to the preparation of slices.…”

FIBRASCAN: A novel method for 3D white matter tract reconstruction in MR space from cadaveric dissection

“…Unfortunately, this stain only diffuses to 20 to 40 mm from the injection point, which is insufficient for large fiber tracts. Polarized light imaging (PLI) records light transmission through an anatomical slice; due to optical birefringence of the myelin sheaths, light transmission depends on the relative orientations of light polarization and fiber tracts (Axer et al, 2001;Dammers et al, 2010;Palm et al, 2010). Refinements of this promising technique can evaluate fiber direction at a micrometer-scale resolution but, as it uses slices, it suffers from the same limitation as histological preparation for axonal tracing, i.e.…”