One Component? Two Components? Three? The Effect of Including a Non-Exchanging ‘Free Water Component in Multicomponent Driven Equilibrium Single Pulse Observation of T1 T2 (mcDESPOT)

摘要

Quantitative myelin content imaging provides novel and pertinent information related to underlying pathogenetic mechanisms of myelin-related disease, or disorders arising from aberrant connectivity. Multicomponent Driven Equilibrium Single Pulse Observation of T1 and T2 (mcDESPOT) is a time-efficient multicomponent relaxation analysis technique that provides estimates of the myelin water fraction (MWF), a surrogate measure of myelin volume. Unfortunately, mcDESPOT relies on a two water-pool model (myelin-associated water, and intra/extra cellular water), which is inadequate within partial-volume voxels, i.e. containing brain tissue and ventricle or meninges, resulting in MWF under-estimation. To address this, a third, non-exchanging ‘free-water’ component was introduced to the mcDESPOT model. Numerical simulations and experimental in vivo data show the model to perform advantageously within partial volume regions whilst providing robust and reproducible results. It is concluded that this model is preferable for future studies and analysis.