In vivo Multi-Parameter Mapping of the Habenula using MRI

Abstract

Abstract The habenula is a small, epithalamic brain structure situated between the mediodorsal thalamus and the third ventricle, rostral to the posterior commissure. It plays an important role in the reward circuitry of the brain and is implicated in psychiatric conditions, such as depression. The importance of the habenula for human cognition and mental health make it a key structure of interest for neuroimaging studies However, relatively few studies have been conducted in humans to characterize its physical properties using magnetic resonance imaging as habenula visualization in vivo is challenging, primarily due to its subcortical location and small size. To date, microstructural characterization of the habenula has focused on QSM. In this work we complement this characterization with measures of longitudinal and effective transverse relaxation rates, proton density and magnetisation transfer saturation using a high-resolution quantitative multi-parametric mapping protocol at 3T, in a cohort of 26 healthy participants. The habenula was most clearly visualised on the R1 maps, with highest CNR for each participant. However, its boundaries were consistent across the different parameter maps. We have provided a quantitative multi-parametric characterization which sets baseline measurements that may be useful for sequence optimization to further enhance visualisation, and provide reference values for future studies investigating pathological differences in habenula microstructure.