Abstract
BackgroundA number of imaging factors can affect the orientation distribution function (ODF) reconstruction in high angular resolution diffusion imaging (HARDI). The aim of this study was to investigate the effect of the b-value on the HARDI reconstruction and to seek for the appropriate b-value for ODF reconstruction from clinical HARDI data.MethodsDiffusion MRI data with various b-values were collected on a GE 3T MRI scanner. To reconstruct the diffusion ODF and fiber ODF, decomposition-based spherical polar Fourier imaging and deconvolution-based constrained spherical deconvolution approaches were applied separately. The full width at half maximum (FWHM) of the ODF and the angular difference of the peaks extracted from ODF were measured to investigate the effect of b-value on the ODF reconstruction. Visual inspection of the ODF was used to evaluate the reconstructions.ResultsThe FWHM of the ODFs in the corpus callosum, which was chosen as the region of interest (ROI), decreased with increasing b-values. The differences in the FWHM for the diffusion ODF and the fiber ODF between the b-values of 2000 s/mm2 and 2500 s/mm2 were not significant. The angular differences of the ODF between 2000 s/mm2 and 2500 s/mm2 were lowest in both single-directional and two-directional situations. The ODFs became sharper and crossing-fiber situations were detected with an increase in b-value. B = 2000 s/mm2 and above revealed most of the two-way or three-way crossing-fiber structures.ConclusionsConsidering both the signal-to-noise ratio and the acquisition time, b = 2000 s/mm2 is the basic requirement for ODF reconstruction using current HARDI methods on clinical data. This study can provide a useful reference for researchers and clinicians attempting to set appropriate scan protocols for specific HARDI experiments.
Highlights
In recent years, imaging neuroscience has examined the human brain as a hierarchical and self-organizational network system [1, 2]
The full width at half maximum (FWHM) of the orientation distribution function (ODF) in the corpus callosum, which was chosen as the region of interest (ROI), decreased with increasing b-values
This does not alter the authors' adherence to PLOS ONE Editorial policies and criteria. Considering both the signal-to-noise ratio and the acquisition time, b = 2000 s/mm2 is the basic requirement for ODF reconstruction using current high angular resolution diffusion imaging (HARDI) methods on clinical data
Summary
In recent years, imaging neuroscience has examined the human brain as a hierarchical and self-organizational network system [1, 2]. Diffusion MRI (dMRI) is a non-invasive imaging technique that, to date, is unique in that it can be utilized to reveal the microstructure of the white matter of the in-vivo human brain [8]. One is traditional diffusion tensor imaging (DTI), for which a Gaussian model was adopted to represent the distribution of water molecules [9]. Deconvolution-based methods have been proposed by many researchers [19,20,21] as ways to estimate the fiber ODF directly rather than indirectly through the diffusion ODF. The diffusion ODF represents the motion of water molecules, which often, but not exclusively, diffuse parallel to the fiber, whereas the fiber ODF describes the distribution of the nerve fiber directions within a voxel [22]. The aim of this study was to investigate the effect of the b-value on the HARDI reconstruction and to seek for the appropriate b-value for ODF reconstruction from clinical HARDI data
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