Illustrative White Matter Fiber Bundles

Abstract

Diffusion Tensor Imaging (DTI) has made feasible the visualization of the fibrous structure of the brain white matter. In the last decades, several fiber-tracking methods have been developed to reconstruct the fiber tracts from DTI data. Usually these fiber tracts are shown individually based on some selection criteria like region of interest. However, if the white matter as a whole is being visualized clutter is generated by directly rendering the individual fiber tracts. Often users are actually interested in fiber bundles, anatomically meaningful entities that abstract from the fibers they contain. Several clustering techniques have been developed that try to group the fiber tracts in fiber bundles. However, even if clustering succeeds, the complex nature of white matter still makes it difficult to investigate. In this paper, we propose the use of illustration techniques to ease the exploration of white matter clusters. We create a technique to visualize an individual cluster as a whole. The amount of fibers visualized for the cluster is reduced to just a few hint lines, and silhouette and contours are used to improve the definition of the cluster borders. Multiple clusters can be easily visualized by a combination of the single cluster visualizations. Focus+context concepts are used to extend the multiple-cluster renderings. Exploded views ease the exploration of the focus cluster while keeping the context clusters in an abstract form. Real-time results are achieved by the GPU implementation of the presented techniques.

A Survey of Illustrative Visualization Techniques for Diffusion-Weighted MRI Tractography

“…The initial concept of extracting a dedicated bundle surface from a set of related fiber tracts was extended by Röttger et al [56] in their BundleExplorer tool. BundleExplorer uses semi-transparent bundle surfaces with silhouettes and explicitly [46,47] fiber bundling approach using 2D line halos.…”

“…In a less traditional approach, Otten et al [46,47] use fiber tract clustering to derive a set of related tracts which they then depict using an illustrative rendering technique that does not actually need to derive an intermediary wrapped surface geometry. Instead, they still process all extracted fiber tracts individually for the visualization, but render each of them with a relatively wide halo they color based on the fiber bundle.…”

“…12). 13 To emphasize this effect, Otten et al [46,47] add an image-space contour around each of these colored shapes. Finally, to better indicate the directionality of the fibers within each bundle, they add what they call "hint lines"-a fiber tract rendering in which only the top-most lines remain visible due to the occlusion by the tract halos.…”

Illustrative uncertainty visualization of DTI fiber pathways

“…An illustrative confidence interval is the visual representation of these fibers and shows the variation in fiber pathways due to noise and modeling error. The rendering algorithm uses a silhouette and outline representation that is based on the work of Otten et al [23], but we extend it with additional visual styles, interaction features, Focus+Context views, and anatomical context. Furthermore, we apply and evaluate our approach in the context of neurosurgical risk assessment and decision-making.…”

“…An outline is defined as the border of a silhouette. Otten et al [23] presented an approach to render silhouettes and outlines for sets of clustered fibers using a GPU-accelerated algorithm. We extend this approach in the following ways:…”