Improving Fiber Alignment in HARDI by Combining Contextual PDE Flow with Constrained Spherical Deconvolution

• Published in: PloS one Vol. 10; no. 10; p. e0138122
• Main Authors: Portegies, J. M., Fick, R. H. J., Sanguinetti, G. R., Meesters, S. P. L., Girard, G., Duits, R.
• Format: Journal Article
• Language: English
• Published: United States Public Library of Science 14.10.2015; Public Library of Science (PLoS)
• Subjects: Algorithms; Alignment; Angular resolution; Brain - pathology; Brain research; Computation; Computer Science; Computer Simulation; Connectivity; Data acquisition; Data processing; Deconvolution; Diffusion; Diffusion Magnetic Resonance Imaging - methods; Diffusion Tensor Imaging - methods; Elongated structure; Epilepsy; Epilepsy - pathology; Epilepsy - surgery; Ethics; False Positive Reactions; Fiber orientation; Humans; Image Interpretation, Computer-Assisted - methods; Image Processing, Computer-Assisted; Lie groups; Magnetic resonance; Magnetic resonance imaging; Mathematics; Medical Imaging; Models, Statistical; NMR; Nuclear magnetic resonance; Pattern Recognition, Automated - methods; Phantoms, Imaging; Probability; Radiation; Reconstruction; Regularization; Regularization methods; Stochastic Processes; Stochasticity; Surgery; White Matter - pathology; France; Netherlands; Diffusion MRI; Tractography
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0138122

We propose two strategies to improve the quality of tractography results computed from diffusion weighted magnetic resonance imaging (DW-MRI) data. Both methods are based on the same PDE framework, defined in the coupled space of positions and orientations, associated with a stochastic process describing the enhancement of elongated structures while preserving crossing structures. In the first method we use the enhancement PDE for contextual regularization of a fiber orientation distribution (FOD) that is obtained on individual voxels from high angular resolution diffusion imaging (HARDI) data via constrained spherical deconvolution (CSD). Thereby we improve the FOD as input for subsequent tractography. Secondly, we introduce the fiber to bundle coherence (FBC), a measure for quantification of fiber alignment. The FBC is computed from a tractography result using the same PDE framework and provides a criterion for removing the spurious fibers. We validate the proposed combination of CSD and enhancement on phantom data and on human data, acquired with different scanning protocols. On the phantom data we find that PDE enhancements improve both local metrics and global metrics of tractography results, compared to CSD without enhancements. On the human data we show that the enhancements allow for a better reconstruction of crossing fiber bundles and they reduce the variability of the tractography output with respect to the acquisition parameters. Finally, we show that both the enhancement of the FODs and the use of the FBC measure on the tractography improve the stability with respect to different stochastic realizations of probabilistic tractography. This is shown in a clinical application: the reconstruction of the optic radiation for epilepsy surgery planning.