Magnetization transfer weighted imaging in the upper cervical spinal cord using cerebrospinal fluid as intersubject normalization reference (MTCSF imaging)

The magnetization transfer ratio (MTR) is a reliable measure of MT effects because it employs an internal standard that allows quantitative comparison between subjects, independent of other contrasts, coil loading, and coil sensitivity profiles. However, at very high spatial resolution in the spinal cord at 1.5 T, the use of MTR quantification has been hampered by low signal-to-noise ratio (SNR) and acute sensitivity to motion. Here, the suitability of cerebrospinal fluid (CSF) as an alternative inter-subject MT signal intensity reference for the spine is evaluated. Contrary to MTR, this so-called MTCSF internal standard does not remove interfering T₁, T₂, and spin density contrast and is not expected to be able to discriminate between myelination and inflammation effects. However, it can detect initial changes in myelination when signal alterations are not yet detectable by conventional MRI. As a first example, this is demonstrated for the noninflammatory spinal cord white matter disease adrenomyeloneuropathy.