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New review in preprint: "Fixel-based Analysis of Diffusion MRI: Methods, Applications, Challenges and Opportunities".Here:
https://doi.org/10.31219/osf.io/zu8fv A collaborative Melbourne lock-down effort to serve the #dMRI community! Please RT, we welcome constructive feedback. [1/11]
![New review in preprint: "Fixel-based Analysis of Diffusion MRI: Methods, Applications, Challenges and Opportunities".Here: https://doi.org/10.31219/osf.io/zu8fv A collaborative Melbourne lock-down effort to serve the #dMRI community! Please RT, we welcome constructive feedback. [1/11]](https://pbs.twimg.com/media/Ene-H_BVkAATJuE.jpg "New review in preprint: \"Fixel-based Analysis of Diffusion MRI: Methods, Applications, Challenges and Opportunities\".Here: https://doi.org/10.31219/osf.io/zu8fv A collaborative Melbourne lock-down effort to serve the #dMRI community! Please RT, we welcome constructive feedback. [1/11]")
Fixel-based Analysis (FBA) is a framework for #diffusion #MRI analysis that allows to extract, process and perform whole-brain stats on fibre-specific measures of WM #microstructure. Statistical results are also fibre-specific, even in presence of crossing fibres! 
[2/11]
![Fixel-based Analysis (FBA) is a framework for #diffusion #MRI analysis that allows to extract, process and perform whole-brain stats on fibre-specific measures of WM #microstructure. Statistical results are also fibre-specific, even in presence of crossing fibres! [2/11]](https://pbs.twimg.com/media/EnfBbUlUYAEYcOh.png "Fixel-based Analysis (FBA) is a framework for #diffusion #MRI analysis that allows to extract, process and perform whole-brain stats on fibre-specific measures of WM #microstructure. Statistical results are also fibre-specific, even in presence of crossing fibres! [2/11]")
Statistical results are also fibre-specific, even in presence of crossing fibres! [2/11]
The framework follows the general structure of the voxel-based analysis (VBA) and voxel-based morphometry (VBM) approaches. But to deal with #dMRI data, fibre distributions and fibre-specific metrics, several additional bespoke steps are required... 
[3/11]
![The framework follows the general structure of the voxel-based analysis (VBA) and voxel-based morphometry (VBM) approaches. But to deal with #dMRI data, fibre distributions and fibre-specific metrics, several additional bespoke steps are required... [3/11]](https://pbs.twimg.com/media/EnfE2mOUYAAtzzq.jpg "The framework follows the general structure of the voxel-based analysis (VBA) and voxel-based morphometry (VBM) approaches. But to deal with #dMRI data, fibre distributions and fibre-specific metrics, several additional bespoke steps are required... [3/11]")
[3/11]
No worries though; while this might look daunting, it's very much feasible. 
In fact, up until 31 August 2020, we identified 54 FBA studies already, across a broad range of healthy and clinical cohorts. In true 2020 style, the trend even looks vaguely exponential. 
[4/11]
![No worries though; while this might look daunting, it's very much feasible. In fact, up until 31 August 2020, we identified 54 FBA studies already, across a broad range of healthy and clinical cohorts. In true 2020 style, the trend even looks vaguely exponential. [4/11]](https://pbs.twimg.com/media/EnfG_3OVoAMBRnf.jpg "No worries though; while this might look daunting, it's very much feasible. In fact, up until 31 August 2020, we identified 54 FBA studies already, across a broad range of healthy and clinical cohorts. In true 2020 style, the trend even looks vaguely exponential. [4/11]")
In fact, up until 31 August 2020, we identified 54 FBA studies already, across a broad range of healthy and clinical cohorts. In true 2020 style, the trend even looks vaguely exponential. [4/11]
And it's certainly worth it, because the brain is full of crossing fibres. If you ever wanted to make sense of those DTI-based FA values that go up or down without sensible explanations, fibre-specific analysis is the way to go (instead)! 
[5/11]
![And it's certainly worth it, because the brain is full of crossing fibres. If you ever wanted to make sense of those DTI-based FA values that go up or down without sensible explanations, fibre-specific analysis is the way to go (instead)! [5/11]](https://pbs.twimg.com/media/EnfLrbVVgAA5Ul7.jpg "And it's certainly worth it, because the brain is full of crossing fibres. If you ever wanted to make sense of those DTI-based FA values that go up or down without sensible explanations, fibre-specific analysis is the way to go (instead)! [5/11]")
[5/11]
Beyond studying microstructural WM densities, FBA also allows to analyse macrostructural changes of fibre-bundle cross-section. Yep, that's indeed a fibre-specific VBM for white matter bundles; also specific to cross-section rather than just any volume change. 
[6/11]
![Beyond studying microstructural WM densities, FBA also allows to analyse macrostructural changes of fibre-bundle cross-section. Yep, that's indeed a fibre-specific VBM for white matter bundles; also specific to cross-section rather than just any volume change. [6/11]](https://pbs.twimg.com/media/EnfOF8_UUAIvfXO.jpg "Beyond studying microstructural WM densities, FBA also allows to analyse macrostructural changes of fibre-bundle cross-section. Yep, that's indeed a fibre-specific VBM for white matter bundles; also specific to cross-section rather than just any volume change. [6/11]")
[6/11]
Combining the analysis of microstructural fibre density and macrostructural fibre-bundle cross-section opens up a unique spectrum of possibilities. 
This is where things get really fun. 
Ok, maybe also a bit challenging at times. 
[7/11]
![Combining the analysis of microstructural fibre density and macrostructural fibre-bundle cross-section opens up a unique spectrum of possibilities. This is where things get really fun. Ok, maybe also a bit challenging at times. [7/11]](https://pbs.twimg.com/media/EnfP_yOUcAEdRbY.jpg "Combining the analysis of microstructural fibre density and macrostructural fibre-bundle cross-section opens up a unique spectrum of possibilities. This is where things get really fun. Ok, maybe also a bit challenging at times. [7/11]")
This is where things get really fun. Ok, maybe also a bit challenging at times. [7/11]
We don't shy away from pointing out those challenges though. No framework is perfect, and the more complicated it is, the more opportunities for unexpected surprises. 
We discuss a whole range of topics, including: a comparison to other analysis strategies, ... [8/11]
We discuss a whole range of topics, including: a comparison to other analysis strategies, ... [8/11]
...requirements and effects of acquisition parameters, challenges with interpretation of results, multimodal studies, behavioural relevance of results, longitudinal studies, dealing with WM lesions, some limitations, but also future challenges and opportunities. 
[9/11]
[9/11]
Also, a complete overview of (54) current FBA studies. And summaries of the results and conclusions of each one of those. 
There are so, so many conclusions. 
SO WE WELCOME YOUR CONSTRUCTIVE FEEDBACK [10/11]
There are so, so many conclusions. SO WE WELCOME YOUR CONSTRUCTIVE FEEDBACK [10/11]
Did we get something wrong? ...maybe even the conclusions of *your* FBA study? Is something not clear? Can we constructively improve to better serve the community with this review? Get in touch asap, and let us know. 
If it helps, you get acknowledged, naturally. [11/11]
Is something not clear? Can we constructively improve to better serve the community with this review? Get in touch asap, and let us know. If it helps, you get acknowledged, naturally. [11/11]
This would all have been not even close to possible without the work and support of all co-authors. I'm immensely grateful to all of them: @adam_clemente_; @MervynSingh1; @FrederiqueMCB; @OrenCivier; Juan D. Duque; Natalia Egorova; @pe7en7; Ian Fuelscher; Sanuji Gajamange, ...
... @drsilagenc; @ElieGottlieb; Christian Hyde; @PhoebeImms; @Claire_E_Kelly; @MKirkovski; @Scott_Kolbe; @imagetchliang; @Atul_Monash; Remika Mito; @Govinrp; @silk_tim; David N. Vaughan; Julien Zanin; @DavidRaffelt and @KCaeyenberghs. 
On a personal note, this is also one of the things that kept me going in a difficult time. Science is supposed to be a collaborative effort, and nice when it works out like that. It's a testament to the value of local research communities @ISMRM_ANZ @OHBM_Australia. Thank-you.
