To measure water diffusion, a pair of pulsed magnetic field gradients has to be applied.
Specialized diffusion MRI acquisitions that measure water diffusion in multiple directions combined with advanced processing methods convert the acquired signal into diffusion tensor maps and into various other scalar maps that provide additional information about the WM tracts in the brain.
DTI is a technique that measures the water diffusion profile in brain tissue.
Specifically, DTI measures the water diffusion situation in neural fibre so that it is frequently used to investigate the abnormal diffusion in the brain.
Mean diffusivity (MD) provides a general measure of water diffusion without differentiating the direction of diffusivity.
An alternative, but less specific approach has been to use MRI measures of water diffusion through the extracellular space as an indirect measure of tumor cellularity [ 19, 73].
Given these limitations of DTI, alternative diffusion MRI models measuring non-Gaussian water diffusion, such as diffusion kurtosis (Jensen et al. 2005; Veraart et al. 2011b), may be more sensitive for probing microstructural changes in regions with complex tissue architectures (Wu and Cheung 2010; Blockx et al. 2012).
ADC is an overall measure of water diffusion, and given the size of imaging voxels relative to the microstructural environment, includes intracellular and extracellular spaces [40].
Diffusion tensor (DT -MRI parameters, incluDT -MRIan and radial diffusivity (MD and RD, resparameters, and fractincludingsotropy (FA), which describe local meanures of wandradialusion andiffusivityy, have been shown to change throughout childhood and adolescence (Lebel et al. 2008).
DTI measures anisotropic water diffusion that occurs because of physiological borders such as axon bundles and myelin sheaths in the white matter of the brain and spinal cord [ 9, 10, 13].
