Browsing by Subject "diffusion MRI"

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    Application of phase-based motion outlier detection to infant dMRI
    (ISMRM, 2020) Elsaid, Nahla M. H.; Zhuo, Jiachen; Prince, Jerry L.; Wu, Yu-Chien; Radhakrishnan, Rupa; Radiology and Imaging Sciences, School of Medicine
    Detecting and eliminating motion-corrupted slices is crucial in diffusion MRI (dMRI), and particularly essential in imaging neonates. Conventional magnitude-based outlier rejection methods are intensity-based and can usually detect and correct intra-volume movement but can miss outliers in cases of small continuous motions. Phase-based methods can be used to detect motion independently, regardless of the slice-to-volume location. The phase-based method is reasonably accurate and computationally fast, and may be better suited for real-time detection of motion in dMRI. Combining magnitude and phase methods could produce the best results. Here, we evaluate the phase-based method versus the magnitude-based method in neonatal data.
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    Inter-site and inter-scanner diffusion MRI data harmonization
    (Elsevier, 2016-07) Mirzaalian, H.; Ning, L.; Savadjiev, P.; Pasternak, O.; Bouix, S.; Michailovich, O.; Grant, G.; Marx, C. E.; Morey, R. A.; Flashman, L. A.; George, M. S.; McAllister, Thomas W.; Andaluz, N.; Shutter, L.; Coimbra, R.; Zafonte, R. D.; Coleman, M. J.; Kubicki, M.; Westin, C. F.; Stein, M. B.; Shenton, M. E.; Rathi, Y.; Department of Psychiatry, IU School of Medicine
    We propose a novel method to harmonize diffusion MRI data acquired from multiple sites and scanners, which is imperative for joint analysis of the data to significantly increase sample size and statistical power of neuroimaging studies. Our method incorporates the following main novelties: i) we take into account the scanner-dependent spatial variability of the diffusion signal in different parts of the brain; ii) our method is independent of compartmental modeling of diffusion (e.g., tensor, and intra/extra cellular compartments) and the acquired signal itself is corrected for scanner related differences; and iii) inter-subject variability as measured by the coefficient of variation is maintained at each site. We represent the signal in a basis of spherical harmonics and compute several rotation invariant spherical harmonic features to estimate a region and tissue specific linear mapping between the signal from different sites (and scanners). We validate our method on diffusion data acquired from seven different sites (including two GE, three Philips, and two Siemens scanners) on a group of age-matched healthy subjects. Since the extracted rotation invariant spherical harmonic features depend on the accuracy of the brain parcellation provided by Freesurfer, we propose a feature based refinement of the original parcellation such that it better characterizes the anatomy and provides robust linear mappings to harmonize the dMRI data. We demonstrate the efficacy of our method by statistically comparing diffusion measures such as fractional anisotropy, mean diffusivity and generalized fractional anisotropy across multiple sites before and after data harmonization. We also show results using tract-based spatial statistics before and after harmonization for independent validation of the proposed methodology. Our experimental results demonstrate that, for nearly identical acquisition protocol across sites, scanner-specific differences can be accurately removed using the proposed method.