Diffusion Weighted Imaging (DWI) has been one of the most widely recognised neuroimaging techniques for evaluating the microstructure of white matter in the brain, with white matter integrity critical to normal brain structure and function. Various diffusion weighted imaging measures have been developed to investigate white matter but all have had inherent limitations.
Published in NeuroImage, our research indicates that the measure we developed – named ‘Difference in Distribution Function’ will ultimately assist in monitoring the ageing process and brain changes seen in cerebrovascular disorders especially dementias. DDF can be used as a marker for monitoring the white matter microstructural changes and ageing related cognitive decline in the older brains. DDF is a flexible framework under which different DWI maps could be used. The biological meaning of DDF is mainly the underpinning of the original DWI maps applied. From the mathematical perspective, it is the parameter which describes the shift between the target MD (if we use mean-diffusivity maps in our computation) distribution and the MD distribution of a reference. If the computation is based on the MD distribution, it will then reflect the accumulative difference of all the voxels in the MD maps of a subject and a reference.
Our software is flexible and easy to use. In addition to the whole brain, region of interest (ROI) analysis can also be conducted to evaluate the regional DDF for local anatomical information. As an example, DDFs can be separately computed for all the ROIs of the JHU white matter tractography atlas (probability threshold at 0.25) (see the figure).
If you used DDF, please cite: Jing Du, Forrest C. Koch, Aihua Xia, Jiyang Jiang, John D. Crawford, Ben C. P. Lam, Anbupalam Thalamuthu, Teresa Lee, Nicole Kochan, Chloe Fawns-Ritchie, Henry Brodaty, Qun Xue, Perminder S. Sachdev, Wei Wen. Difference in distribution functions: A new diffusion weighted imaging metric for estimating white matter integrity. NeuroImage, Volume 240, 15 October 2021, 118381
Figure: JHU white matter tractography atlas (probability threshold at 0.25)
ATR, Anterior thalamic radiation; CGC, Cingulum (cingulate gyrus); CGH, Cingulum (hippocampus); CST, Corticospinal tract; Fmajor, Forceps major; Fminor, Forceps minor; IFO, Inferior fronto-occipital fasciculus; ILF, Inferior longitudinal fasciculus; SLF, Superior longitudinal fasciculus; SLFt, Superior longitudinal fasciculus (temporal part); UNC, Uncinate fasciculus