What is a voxel in DTI?
Unlike traditional medical images, DTI at each voxel is a 3×3 symmetric positive definite matrix with 6 independent elements. Then, scalar indices, such as fractional anisotropy (FA), mean diffusivity (MD) and eigenvalues, can be calculated from a tensor.
What is DTI analysis?
Diffusion tensor imaging (DTI) is a newly developed magnetic resonance imaging (MRI) technique that analyzes the anatomy of nerve cells and a complex neuronal network of the brain.
What are DTI scans used for?
Diffusion tensor imaging tractography, or DTI tractography, is an MRI (magnetic resonance imaging) technique that measures the rate of water diffusion between cells to understand and create a map of the body’s internal structures; it is most commonly used to provide imaging of the brain.
What is voxel-based meta analysis?
Voxel-based meta-analysis (VBM) The ROI is one of the most commonly used methods to address morphometric changes in the brain [2]. This method manually drew and calculated the brain regions of interest by investigators, then compared their volume in AD to HC.
How do MRIs work?
How does MRI work? MRIs employ powerful magnets which produce a strong magnetic field that forces protons in the body to align with that field. When a radiofrequency current is then pulsed through the patient, the protons are stimulated, and spin out of equilibrium, straining against the pull of the magnetic field.
What is true of voxel based morphometry?
Voxel-based morphometry (VBM) is a neuroimaging technique that investigates focal differences in brain anatomy. The core process of VBM is segmenting the brain into grey matter, white matter, and cerebrospinal fluid, warping the segmented images to a template space and smoothing.
What is DSI imaging?
Diffusion spectrum imaging (DSI) is an advanced magnetic resonance imaging (MRI) technique that display crossing fibers and complex intravoxel fiber orientation distributions reliably and accurately [7].
Is DTI functional or structural?
Thus, DTI provides information about structural connectivity, as compared to functional connectivity data from rsFMRI. Perhaps most importantly, DTI can illustrate to the surgeon the relationship of a tumor to underlying white matter tracts.
What are the limitations of DTI?
A limitation of DTI is that it currently has a low signal to noise ratio (SNR), which may increase scanning times. SNR compares the level of background noise to the level of the signal obtained. When the noise is too great in comparison to the signal (low SNR), image quality is poor.
Why use voxel-based morphometry?
Voxel-based morphometry (VBM) is one such automated technique that has grown in popularity since its introduction (Wright et al., 1995; Ashburner and Friston, 2000), largely because of the fact that it is relatively easy to use and has provided biologically plausible results.
What is a voxel-wise DTI analysis?
Voxel-wise analysis of DTI is characterized by spatial normalization of DTI, statistical analysis including hypothesis test at each voxel and multiple comparison correction. The major challenges in voxel-wise DTI analysis include high quality voxel correspondence and multiple comparison correction in hypothesis test.
What is the difference between voxel-wise and spatially localized analysis?
In some situations when more spatially localized properties should be considered, voxel-wise analysis as an alternative method, may perform better. Voxel-wise analysis of DTI is characterized by spatial normalization of DTI, statistical analysis including hypothesis test at each voxel and multiple comparison correction.
What is the best way to analyze DTI?
Most statistical analyses of DTI are based on region-of-interest (ROI) methods, which usually involve manual ROI delineations and the statistical analysis of the averaged tensor indices within the ROIs. This kind of analyses often suffers from large intra and inter-person variability and bias in defining meaningful ROIs.
Is voxel-wise analysis the best way to measure Rois?
This kind of analyses often suffers from large intra and inter-person variability and bias in defining meaningful ROIs. In some situations when more spatially localized properties should be considered, voxel-wise analysis as an alternative method, may perform better.