Abstract Cell membranes and macromolecules or paramagnetic compounds interact with water proton spins, which modulates magnetic resonance imaging (MRI) contrast providing information on tissue composition. For a further investigation, quantitative magnetization transfer (qMT) parameters (at 3T), including the ratio of the macromolecular and water proton pools, ℱ, and the exchange-rate constant as well as the (observed) longitudinal and the effective transverse relaxation rates (at 3T and 7T), and respectively, were measured at high spatial resolution (200 μm) in a slice of fixed marmoset brain and compared to histology results obtained with Gallyas’ myelin stain and Perls’ iron stain. and were linearly correlated with the iron content for the entire slice, whereas distinct differences were obtained between gray and white matter for correlations of relaxometry and qMT parameters with myelin content. The combined results suggest that the macromolecular pool interacting with water consists of myelin and (less efficient) non-myelin contributions. Despite strong correlation of ℱ and none of these parameters was uniquely specific to myelination. Due to additional sensitivity to iron stores, and were more sensitive for depicting microstructural differences between cortical layers than ℱ. Highlights MRI (200μm) is correlated with myelin and iron histology in fixed marmoset brain. Detailed z -spectra are employed for precise magnetization-transfer (MT) measurements. Longitudinal and effective transverse relaxation rates depend linearly on tissue iron. Longitudinal relaxation and MT are not uniquely specific to myelin. Myelin and non-myelin macromolecules impact water relaxation and MT contrast.

High-Resolution Magnetization-Transfer Imaging of Post-Mortem Marmoset Brain: Comparisons with Relaxometry and Histology