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

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), [Formula] and [Formula] respectively, were measured at high spatial resolution (200 m) in a slice of fixed marmoset brain and compared to histology results obtained with Gallyas myelin stain and Perls iron stain. [Formula] and [Formula] 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 [Formula] none of these parameters was uniquely specific to myelination. Due to additional sensitivity to iron stores, [Formula] and [Formula] were more sensitive for depicting microstructural differences between cortical layers than [F]. HighlightsO_LIMRI (200m) is correlated with myelin and iron histology in fixed marmoset brain. C_LIO_LIDetailed z-spectra are employed for precise magnetization-transfer (MT) measurements. C_LIO_LILongitudinal and effective transverse relaxation rates depend linearly on tissue iron. C_LIO_LILongitudinal relaxation and MT are not uniquely specific to myelin. C_LIO_LIMyelin and non-myelin macromolecules impact water relaxation and MT contrast. C_LI