However, such a ground truth regarding the fiber connectivity within the entire brain is very difficult to obtain. In order to assess the confidence we may place in results from different tractography methods and to gain deeper insight into the nature of the various problems, validation against a “ground truth” would be invaluable. While the resulting fiber pathways certainly contain valuable information about the underlying architecture, they are subject to a number of serious pitfalls and limitations. Tractography is a class of techniques that aim to extract information about white matter fiber systems from diffusion‐weighted magnetic resonance imaging (dwMRI) data. © 2015 The Authors Human Brain Mapping Published by Wiley Periodicals, Inc. In particular, the increase of spatial resolution, under preservation of the signal‐to‐noise‐ratio, is key. Instead, the crucial challenge in making tractography a truly useful and reliable tool in brain research and neurology lies in the acquisition of better data. Closer inspection of the results led to the conclusion that these problems mainly originate from regions with complex fiber arrangements or high curvature and are not easily resolved by sophisticated local models alone. However, false positive connections were very common and, in particular, we discovered that it is not possible to achieve high sensitivity (i.e., few false negatives) and high specificity (i.e., few false positives) at the same time. While the voxel‐wise agreement was very limited, qualitative assessment revealed that tractography is capable of finding the major fiber tracts, although there were some differences between the methods. A representative selection of tractography methods were compared to manganese tracing on a voxel‐wise basis, and a more qualitative assessment examined whether, and to what extent, certain fiber tracts and gray matter targets were reached. In this study, we used invasive tracing to evaluate white matter tractography methods based on ex vivo diffusion‐weighted magnetic resonance imaging (dwMRI) data.
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