Tractography dissection variability: what happens when 42 groups dissect 14 white matter bundles on the same dataset?
Authors: Schilling Kurt G. , Rheault François , Petit Laurent , Hansen Colin B. , Nath Vishwesh , Yeh Fang-Cheng , Girard Gabriel , Barakovic Muhamed , Rafael-Patino Jonathan , Yu Thomas , Fischi-Gomez Elda , Pizzolato Marco , Ocampo-Pineda Mario , Schiavi Simona , Canales-Rodríguez Erick J. , Daducci Alessandro , Granziera Cristina , Innocenti Giorgio , Thiran Jean-Philippe , Mancini Laura , Wastling Stephen , Cocozza Sirio , Petracca Maria , Pontillo Giuseppe , Mancini Matteo , Vos Sjoerd B. , Vakharia Vejay N. , Duncan John S. , Melero Helena , Manzanedo Lidia , Sanz-Morales Emilio , Peña-Melián Ángel , Calamante Fernando , Attyé Arnaud , Cabeen Ryan P. , Korobova Laura , Toga Arthur W. , Vijayakumari Anupa Ambili , Parker Drew , Verma Ragini , Radwan Ahmed , Sunaert Stefan , Emsell Louise , De Luca Alberto , Leemans Alexander , Bajada Claude J. , Haroon Hamied , Azadbakht Hojjatollah , Chamberland Maxime , Genc Sila , Tax Chantal M. W. , Yeh Ping-Hong , Srikanchana Rujirutana , Mcknight Colin D. , Yang Joseph Yuan-Mou , Chen Jian , Kelly Claire E. , Yeh Chun-Hung , Cochereau Jerome , Maller Jerome J. , Welton Thomas , Almairac Fabien , Seunarine Kiran K , Clark Chris A. , Zhang Fan , Makris Nikos , Golby Alexandra , Rathi Yogesh , O’Donnell Lauren J. , Xia Yihao , Aydogan Dogu Baran , Shi Yonggang , Fernandes Francisco Guerreiro , Raemaekers Mathijs , Warrington Shaun , Michielse Stijn , Ramírez-Manzanares Alonso , Concha Luis , Aranda Ramón , Meraz Mariano Rivera , Lerma-Usabiaga Garikoitz , Roitman Lucas , Fekonja Lucius S. , Calarco Navona , Joseph Michael , Nakua Hajer , Voineskos Aristotle N. , Karan Philippe , Grenier Gabrielle , Legarreta Jon Haitz , Adluru Nagesh , Nair Veena A. , Prabhakaran Vivek , Alexander Andrew L. , Kamagata Koji , Saito Yuya , Uchida Wataru , Andica Christina , Abe Masahiro , Bayrak Roza G. , Gandini Wheeler-Kingshott Claudia A.M. , D’Angelo Egidio , Palesi Fulvia , Savini Giovanni , Rolandi Nicolò , Guevara Pamela , Houenou Josselin , López-López Narciso , Mangin Jean-François , Poupon Cyril , Román Claudio , Vázquez Andrea , Maffei Chiara , Arantes Mavilde , Andrade José Paulo , Silva Susana Maria , Calhoun Vince D. , Caverzasi Eduardo , Sacco Simone , Lauricella Michael , Pestilli Franco , Bullock Daniel , Zhan Yang , Brignoni-Perez Edith , Lebel Catherine , Reynolds Jess E , Nestrasil Igor , Labounek René , Lenglet Christophe , Paulson Amy , Aulicka Stefania , Heilbronner Sarah R. , Heuer Katja , Chandio Bramsh Qamar , Guaje Javier , Tang Wei , Garyfallidis Eleftherios , Raja Rajikha , Anderson Adam W. , Landman Bennett A. , Descoteaux Maxime 
Published: October 2020

White matter bundle segmentation using diffusion MRI fiber tractography has become the method of choice to identify white matter fiber pathwaysin vivoin human brains. However, like other analyses of complex data, there is considerable variability in segmentation protocols and techniques. This can result in different reconstructions of the same intended white matter pathways, which directly affects tractography results, quantification, and interpretation. In this study, we aim to evaluate and quantify the variability that arises from different protocols for bundle segmentation. Through an open call to users of fiber tractography, including anatomists, clinicians, and algorithm developers, 42 independent teams were given processed sets of human whole-brain streamlines and asked to segment 14 white matter fascicles on six subjects. In total, we received 57 different bundle segmentation protocols, which enabled detailed volume-based and streamline-based analyses of agreement and disagreement among protocols for each fiber pathway. Results show that even when given the exact same sets of underlying streamlines, the variability across protocols for bundle segmentation is greater than all other sources of variability in the virtual dissection process, including variability within protocols and variability across subjects. In order to foster the use of tractography bundle dissection in routine clinical settings, and as a fundamental analytical tool, future endeavors must aim to resolve and reduce this heterogeneity. Although external validation is needed to verify the anatomical accuracy of bundle dissections, reducing heterogeneity is a step towards reproducible research and may be achieved through the use of standard nomenclature and definitions of white matter bundles and well-chosen constraints and decisions in the dissection process.