Abstract
Investigative studies of white matter (WM) brain structures using diffusion MRI (dMRI) tractography frequently require manual WM bundle segmentation, often called “virtual dissection.” Human errors and personal decisions make these manual segmentations hard to reproduce, which have not yet been quantified by the dMRI community. It is our opinion that if the field of dMRI tractography wants to be taken seriously as a widespread clinical tool, it is imperative to harmonize WM bundle segmentations and develop protocols aimed to be used in clinical settings. The EADC‐ADNI Harmonized Hippocampal Protocol achieved such standardization through a series of steps that must be reproduced for every WM bundle. This article is an observation of the problematic. A specific bundle segmentation protocol was used in order to provide a real‐life example, but the contribution of this article is to discuss the need for reproducibility and standardized protocol, as for any measurement tool. This study required the participation of 11 experts and 13 nonexperts in neuroanatomy and “virtual dissection” across various laboratories and hospitals. Intra‐rater agreement (Dice score) was approximately 0.77, while inter‐rater was approximately 0.65. The protocol provided to participants was not necessarily optimal, but its design mimics, in essence, what will be required in future protocols. Reporting tractometry results such as average fractional anisotropy, volume or streamline count of a particular bundle without a sufficient reproducibility score could make the analysis and interpretations more difficult. Coordinated efforts by the diffusion MRI tractography community are needed to quantify and account for reproducibility of WM bundle extraction protocols in this era of open and collaborative science.
Highlights
Diffusion MRI tractography reconstructs streamlines that model the white matter (WM) neuroanatomy
The range of values for segmentation measures is wider for nonexperts, meaning that either intra-rater or inter-rater variability is likely higher
The fact that segmentations with low spatial overlap have the same average fractional anisotropy (FA) shows that reporting this measurement to gain insight about reproducibility of bundle segmentation is far from optimal
Summary
Diffusion MRI (dMRI) tractography reconstructs streamlines that model the white matter (WM) neuroanatomy. When specific hypotheses about known pathways, that is, WM bundles, are investigated, neuroanatomists design “dissection plans” that contain anatomical landmarks and instructions to isolate the bundle of interest from this whole brain tractogram (Bayrak et al, 2019; Catani & De Schotten, 2008; Catani, Howard, Pajevic, & Jones, 2002; Chenot et al, 2019; Hau et al, 2016). Bundles can be segmented to study WM morphology, asymmetries, and can be associated with specific functions (Catani et al, 2007; Groeschel et al, 2014; Lee Masson, Wallraven, & Petit, 2017; Masson, Kang, Petit, & Wallraven, 2018) with approaches similar to other brain structures (Lister & Barnes, 2009; Reitz et al, 2009). There are no standardized method being used by the community
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
