1- *Eddymotion *
1+ *NiFreeze *
22============
3- Estimating head-motion and deformations derived from eddy-currents in diffusion MRI data.
3+ An open-source framework for volume-to-volume motion estimation in d/fMRI and PET,
4+ and Eddy-current-derived distortion estimation in dMRI.
45
56.. image :: https://zenodo.org/badge/DOI/10.5281/zenodo.4680599.svg
67 :target: https://doi.org/10.5281/zenodo.4680599
@@ -26,41 +27,47 @@ Estimating head-motion and deformations derived from eddy-currents in diffusion
2627 :target: https://github.com/nipreps/nifreeze/actions/workflows/pythonpackage.yml
2728 :alt: Python package
2829
29- Retrospective estimation of head-motion between diffusion-weighted images (DWI) acquired within
30- diffusion MRI (dMRI) experiments renders exceptionally challenging1 for datasets including
31- high-diffusivity (or “high b”) images.
32- These “high b” (b > 1000s/mm2) DWIs enable higher angular resolution, as compared to more traditional
33- diffusion tensor imaging (DTI) schemes.
34- UNDISTORT [#r1 ]_ (Using NonDistorted Images to Simulate a Template Of the Registration Target)
35- was the earliest method addressing this issue, by simulating a target DW image without motion
36- or distortion from a DTI (b=1000s/mm2) scan of the same subject.
37- Later, Andersson and Sotiropoulos [#r2 ]_ proposed a similar approach (widely available within the
38- FSL ``eddy `` tool), by predicting the target DW image to be registered from the remainder of the
39- dMRI dataset and modeled with a Gaussian process.
40- Besides the need for less data, ``eddy `` has the advantage of implicitly modeling distortions due
41- to Eddy currents.
42- More recently, Cieslak et al. [#r3 ]_ integrated both approaches in *SHORELine *, by
43- (i) setting up a leave-one-out prediction framework as in eddy; and
44- (ii) replacing eddy’s general-purpose Gaussian process prediction with the SHORE [#r4 ]_ diffusion model.
45-
46- *Eddymotion * is an open implementation of eddy-current and head-motion correction that builds upon
47- the work of ``eddy `` and *SHORELine *, while generalizing these methods to multiple acquisition schemes
48- (single-shell, multi-shell, and diffusion spectrum imaging) using diffusion models available with DIPY [#r5 ]_.
30+ Diffusion and functional MRI (d/fMRI) generally employ echo-planar imaging (EPI) for fast
31+ whole-brain acquisition.
32+ Despite the rapid collection of volumes, typical repetition times are long enough for head motion
33+ to occur, which has been proven detrimental to both diffusion [1 ]_ and functional [2 ]_ MRI.
34+ In the case of dMRI, additional volume-wise, low-order spatial distortions are caused by
35+ eddy currents (EC), which appear as a result of quickly switching diffusion gradients.
36+ Unaccounted for EC distortion can result in incorrect local model fitting and poor downstream
37+ tractography results [3 ]_, [4 ]_.
38+ *FSL *'s ``eddy `` [5 ]_ is the most popular tool for EC distortion correction, and
39+ implements a leave-one-volume-out approach to estimate EC distortions.
40+ However, *FSL * has commercial restrictions that hinder application within open-source initiatives
41+ such as *NiPreps * [6 ]_.
42+ In addition, *FSL *'s development model discourages the implementation of alternative data-modeling
43+ approaches to broaden the scope of application (e.g., modalities beyond dMRI).
44+ *NiFreeze * is an open-source implementation of ``eddy ``'s approach to estimate artifacts
45+ that permits alternative models that apply to, for instance, head motion estimation in fMRI
46+ and positron-emission tomography (PET) data.
4947
5048.. BEGIN FLOWCHART
5149
52- .. image :: https://raw.githubusercontent.com/nipreps/nifreeze/507fc9bab86696d5330fd6a86c3870968243aea8 /docs/_static/nifreeze-flowchart.svg
50+ .. image :: https://raw.githubusercontent.com/nipreps/nifreeze/9588b4d0e410cc648f73f5581eb8feb38baf6e2b /docs/_static/nifreeze-flowchart.svg
5351 :alt: The nifreeze flowchart
5452
5553.. END FLOWCHART
5654
57- .. [#r1 ] S. Ben-Amitay et al., Motion correction and registration of high b-value diffusion weighted images, Magnetic
58- Resonance in Medicine 67:1694–1702 (2012)
59- .. [#r2 ] J. L. R. Andersson. et al., An integrated approach to correction for off-resonance effects and subject movement
60- in diffusion MR imaging, NeuroImage 125 (2016) 1063–1078
61- .. [#r3 ] M. Cieslak et al., QSIPrep: An integrative platform for preprocessing and reconstructing diffusion MRI data.
62- Nature Methods, 18(7), 775–778 (2021)
63- .. [#r4 ] E. Ozarslan et al., Simple Harmonic Oscillator Based Reconstruction and Estimation for Three-Dimensional Q-Space
64- MRI. in Proc. Intl. Soc. Mag. Reson. Med. vol. 17 1396 (2009)
65- .. [#r5 ] E. Garyfallidis et al., Dipy, a library for the analysis of diffusion MRI data. Front. Neuroinformatics 8, 8
66- (2014)
55+ .. [1 ] Yendiki et al. (2014) *Spurious group differences due to head motion in a diffusion MRI study *.
56+ NeuroImage **88 **:79-90.
57+
58+ .. [2 ] Power et al. (2012) *Spurious but systematic correlations in functional connectivity MRI
59+ networks arise from subject motion *. NeuroImage **59 **:2142-2154.
60+
61+ .. [3 ] Zhuang et al. (2006) *Correction of eddy-current distortions in diffusion tensor images using
62+ the known directions and strengths of diffusion gradients *. J Magn Reson Imaging **24 **:1188-1193.
63+
64+ .. [4 ] Andersson et al. (2012) *A comprehensive Gaussian Process framework for correcting distortions
65+ and movements in difussion images *. In: 20th SMRT & 21st ISMRM, Melbourne, Australia.
66+
67+ .. [5 ] Andersson & Sotiropoulos (2015) *Non-parametric representation and prediction of single- and
68+ multi-shell diffusion-weighted MRI data using Gaussian processes *. NeuroImage **122 **:166-176.
69+
70+ .. [6 ] Esteban (2025) *Standardized preprocessing in neuroimaging: enhancing reliability and reproducibility *.
71+ In: Whelan, R., & Lemaître, H. (eds.) *Methods for Analyzing Large Neuroimaging Datasets. Neuromethods *,
72+ vol. **218 **, pp. 153-179. Humana, New York, NY.
73+ doi:`10.1007/978-1-0716-4260-3_8 <https://doi.org/10.1007/978-1-0716-4260-3_8 >`__.
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