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      Dipy, a library for the analysis of diffusion MRI data

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          Abstract

          Diffusion Imaging in Python (Dipy) is a free and open source software project for the analysis of data from diffusion magnetic resonance imaging (dMRI) experiments. dMRI is an application of MRI that can be used to measure structural features of brain white matter. Many methods have been developed to use dMRI data to model the local configuration of white matter nerve fiber bundles and infer the trajectory of bundles connecting different parts of the brain. Dipy gathers implementations of many different methods in dMRI, including: diffusion signal pre-processing; reconstruction of diffusion distributions in individual voxels; fiber tractography and fiber track post-processing, analysis and visualization. Dipy aims to provide transparent implementations for all the different steps of dMRI analysis with a uniform programming interface. We have implemented classical signal reconstruction techniques, such as the diffusion tensor model and deterministic fiber tractography. In addition, cutting edge novel reconstruction techniques are implemented, such as constrained spherical deconvolution and diffusion spectrum imaging (DSI) with deconvolution, as well as methods for probabilistic tracking and original methods for tractography clustering. Many additional utility functions are provided to calculate various statistics, informative visualizations, as well as file-handling routines to assist in the development and use of novel techniques. In contrast to many other scientific software projects, Dipy is not being developed by a single research group. Rather, it is an open project that encourages contributions from any scientist/developer through GitHub and open discussions on the project mailing list. Consequently, Dipy today has an international team of contributors, spanning seven different academic institutions in five countries and three continents, which is still growing.

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          Most cited references49

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          Robust determination of the fibre orientation distribution in diffusion MRI: non-negativity constrained super-resolved spherical deconvolution.

          Diffusion-weighted (DW) MR images contain information about the orientation of brain white matter fibres that potentially can be used to study human brain connectivity in vivo using tractography techniques. Currently, the diffusion tensor model is widely used to extract fibre directions from DW-MRI data, but fails in regions containing multiple fibre orientations. The spherical deconvolution technique has recently been proposed to address this limitation. It provides an estimate of the fibre orientation distribution (FOD) by assuming the DW signal measured from any fibre bundle is adequately described by a single response function. However, the deconvolution is ill-conditioned and susceptible to noise contamination. This tends to introduce artefactual negative regions in the FOD, which are clearly physically impossible. In this study, the introduction of a constraint on such negative regions is proposed to improve the conditioning of the spherical deconvolution. This approach is shown to provide FOD estimates that are robust to noise whilst preserving angular resolution. The approach also permits the use of super-resolution, whereby more FOD parameters are estimated than were actually measured, improving the angular resolution of the results. The method provides much better defined fibre orientation estimates, and allows orientations to be resolved that are separated by smaller angles than previously possible. This should allow tractography algorithms to be designed that are able to track reliably through crossing fibre regions.
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            Nipype: A Flexible, Lightweight and Extensible Neuroimaging Data Processing Framework in Python

            Current neuroimaging software offer users an incredible opportunity to analyze their data in different ways, with different underlying assumptions. Several sophisticated software packages (e.g., AFNI, BrainVoyager, FSL, FreeSurfer, Nipy, R, SPM) are used to process and analyze large and often diverse (highly multi-dimensional) data. However, this heterogeneous collection of specialized applications creates several issues that hinder replicable, efficient, and optimal use of neuroimaging analysis approaches: (1) No uniform access to neuroimaging analysis software and usage information; (2) No framework for comparative algorithm development and dissemination; (3) Personnel turnover in laboratories often limits methodological continuity and training new personnel takes time; (4) Neuroimaging software packages do not address computational efficiency; and (5) Methods sections in journal articles are inadequate for reproducing results. To address these issues, we present Nipype (Neuroimaging in Python: Pipelines and Interfaces; http://nipy.org/nipype), an open-source, community-developed, software package, and scriptable library. Nipype solves the issues by providing Interfaces to existing neuroimaging software with uniform usage semantics and by facilitating interaction between these packages using Workflows. Nipype provides an environment that encourages interactive exploration of algorithms, eases the design of Workflows within and between packages, allows rapid comparative development of algorithms and reduces the learning curve necessary to use different packages. Nipype supports both local and remote execution on multi-core machines and clusters, without additional scripting. Nipype is Berkeley Software Distribution licensed, allowing anyone unrestricted usage. An open, community-driven development philosophy allows the software to quickly adapt and address the varied needs of the evolving neuroimaging community, especially in the context of increasing demand for reproducible research.
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              The NumPy array: a structure for efficient numerical computation

              In the Python world, NumPy arrays are the standard representation for numerical data. Here, we show how these arrays enable efficient implementation of numerical computations in a high-level language. Overall, three techniques are applied to improve performance: vectorizing calculations, avoiding copying data in memory, and minimizing operation counts. We first present the NumPy array structure, then show how to use it for efficient computation, and finally how to share array data with other libraries.
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                Author and article information

                Journal
                Front Neuroinform
                Front Neuroinform
                Front. Neuroinform.
                Frontiers in Neuroinformatics
                Frontiers Media S.A.
                1662-5196
                21 February 2014
                2014
                : 8
                : 8
                Affiliations
                [1] 1Computer Science Department, University of Sherbrooke Sherbrooke, QC, Canada
                [2] 2MRC Cognition and Brain Sciences Unit, University of Cambridge Cambridge, UK
                [3] 3Henry H. Wheeler, Jr. Brain Imaging Center, University of California Berkeley, CA, USA
                [4] 4Department of Neurology and Graduate Group in Bioengineering, University of California San Francisco, CA, USA
                [5] 5Department of Psychology, Stanford University Stanford, CA, USA
                [6] 6Department of Mathematical Sciences, Division of Applied Mathematics, Stellenbosch University Stellenbosch, South Africa
                [7] 7 http://dipy.org/developers.html
                Author notes

                Edited by: Fernando Perez, University of California at Berkeley, USA

                Reviewed by: Krzysztof Gorgolewski, Max Planck Institute for Human Cognitive and Brain Sciences, Germany; Lester Melie-Garcia, Cuban Neuroscience Center, Cuba

                *Correspondence: Eleftherios Garyfallidis, Computer Science Department, University of Sherbrooke, 2500 University Boulevard, Sherbrooke, QC J1K 2R1, Canada e-mail: garyfallidis@ 123456gmail.com

                This article was submitted to the journal Frontiers in Neuroinformatics.

                Article
                10.3389/fninf.2014.00008
                3931231
                24600385
                b5fe11d8-08d7-413c-a83a-de8aade6ddfa
                Copyright © 2014 Garyfallidis, Brett, Amirbekian, Rokem, van der Walt, Descoteaux, Nimmo-Smith and Dipy Contributors.

                This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) or licensor are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

                History
                : 10 October 2013
                : 23 January 2014
                Page count
                Figures: 38, Tables: 1, Equations: 7, References: 98, Pages: 17, Words: 13355
                Categories
                Neuroscience
                Methods Article

                Neurosciences
                diffusion mri,dti,dsi,hardi,dmri,python,free open source software,tractography
                Neurosciences
                diffusion mri, dti, dsi, hardi, dmri, python, free open source software, tractography

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