Fractional T1 Relaxation from Magnetization Transfer in Wood: Applications to Brain MRI?

Spin-lattice (T1) relaxation is widely used in NMR to characterize chemical structure, molecular dynamics, and to provide a contrast mechanism for in-vivo imaging. When tissue is heterogeneous and multicompartment like brain tissue, however, it becomes difficult to model and assign physiological meaning to T1 relaxation due to the transfer of magnetization between pools during relaxation. Using wood as a model system, we explore the deviation from a standard exponential in the relaxation component stemming from this transfer. Fractional calculus offers a generalized exponential function to fit relaxation data from which a potentially unique parameter associated with the sample’s inhomogeneity results. We show the improved fit to the data of the fractional model compared to standard exponentials in wood as well as a lipid bilayer system and posit a white matter mapping technique based on the added fractional fit parameter.