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How does distortion correction correlate with anisotropic indices? A diffusion tensor imaging study.

Dae-Jin Kim·Hae-Jeong Park·Kyung-Whun Kang·Yong-Wook Shin·Jae-Jin Kim·Won-Jin Moon·Eun-Chul Chung·In Young Kim·Jun Soo Kwon·Sun I Kim
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Abstract

PURPOSE: The purpose of this study was to determine a suitable registration algorithm for diffusion tensor imaging (DTI) using conventional preprocessing tools [statistical parametric mapping (SPM) and automated image registration (AIR)] and to investigate how anisotropic indices for clinical assessments are affected by these distortion corrections. MATERIALS AND METHODS: Brain DTI data from 15 normal healthy volunteers were used to evaluate four spatial registration schemes within subjects to correct image distortions: noncorrection, SPM-based affine registration, AIR-based affine registration and AIR-based nonlinear polynomial warping. The performance of each distortion correction was assessed using: (a) quantitative parameters: tensor-fitting error (Ef), mean dispersion index (MDI), mean fractional anisotropy (MFA) and mean variance (MV) within 11 regions of interest (ROI) defined from homogeneous fiber bundles; and (b) fiber tractography through the uncinate fasciculus and the corpus callosum. Fractional anisotropy (FA) and mean diffusivity (MD) were calculated to demonstrate the effects of distortion correction. Repeated-measures analysis of variance was used to investigate differences among the four registration paradigms. RESULTS: AIR-based nonlinear registration showed the best performance for reducing image distortions with respect to smaller Ef (P<.02), MDI (P<.01) and MV (P<.01) with larger MFA (P<.01). FA was decreased to correct distortions (P<.0001) whether the applied registration was linear or nonlinear and was lowest after nonlinear correction (P<.001). No significant differences were found in MD. CONCLUSION: In conventional DTI processing, anisotropic indices of FA can be misestimated by noncorrection or inappropriate distortion correction, which leads to an erroneous increase in FA. AIR-based nonlinear distortion correction would be required for a more accurate measurement of this diffusion parameter.

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AdultAlgorithmsAnisotropyBrainDiffusion Magnetic Resonance ImagingHumansImage EnhancementImage Processing, Computer-AssistedNonlinear DynamicsJournal ArticleResearch Support, Non-U.S. Gov't

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Dae-Jin Kim, Hae-Jeong Park, Kyung-Whun Kang, Yong-Wook Shin, Jae-Jin Kim, Won-Jin Moon, Eun-Chul Chung, In Young Kim, Jun Soo Kwon, Sun I Kim. 2006-10-25. How does distortion correction correlate with anisotropic indices? A diffusion tensor imaging study.. https://doi.org/10.1016/j.mri.2006.07.014

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