Recent work from BIAC researchers Alex Avram, Arnaud Guidon and Allen Song showed progress toward achieving a tissue-specific, in particular, myelin-specific diffusion tensor imaging (DTI). A magnetization transfer (MT) prepared stimulated-echo diffusion tensor imaging (DTI) technique was developed in this research project. The short echo time (TE) enabled by the stimulated-echo acquisition preserves significant signal from the short T2 component (myelin water), and the MT preparation further provides differentiating sensitization to this signal. It was found that this combined strategy could provide sufficient sensitivity in their first attempt to image myelin microstructure. Compared to the diffusion tensor derived from the conventional DTI technique, the myelin water weighted (MWW) tensor has the same principal diffusion direction but exhibits a significant increase in fractional anisotropy (FA), which is mainly due to a decrease in radial diffusivity. These findings are consistent with the microstructural organization of the myelin sheaths that wrap around the axons in the white matter and therefore hinder radial diffusion. Given that many white matter diseases (e.g. multiple sclerosis) begin with a degradation of myelin microanatomy but not a loss of myelin content (e.g. loosening of the myelin sheaths), the newly implemented MWW DTI has the potential to lead to improved assessment of myelin pathology and early detection of demyelination.
Citation: Avram AV, Guidon A, Song AW. Myelin water weighted diffusion tensor imaging. Neuroimage. 2010 Oct 15;53(1):132-8. doi: 10.1016/j.neuroimage.2010.06.019. Epub 2010 Jun 16. PMID: 20587369.