Concurrent saturation transfer contrast in in vivo brain by a uniform magnetization transfer MRI

- The MT effects from white matter and gray matter are asymmetric.
- Several CEST contrast mechanisms in the brain may be buried under the MT effects.
- The uMT technique can separate genuine CEST effects from the background MT effects.
- The uMT technique also measures MT contrast in a more robust way.

The development of chemical exchange saturation transfer (CEST) and magnetization transfer (MT) contrast in MRI has enabled the enhanced detection of metabolites and biomarkers in vivo. In brain MRI, the separation between CEST and MT contrast has been particularly difficult due to overlaps in the frequency responses of the contrast mechanisms. We demonstrate here that MT and CEST contrast can be separated in the brain by the so-called uniform-MT (uMT) technique, thus opening the door to addressing long-standing ambiguities in this field. These methods could be useful for keeping track of important endogenous metabolites and for providing an improved understanding of neurological and neurodegenerative disorders. Examples are shown from white and gray matter regions in healthy volunteers and patients with multiple sclerosis, which demonstrated that the MT effects in the brain were asymmetric and that the uMT method could make them uniform.

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