Magnetic resonance T1–T2* and T1ρ–T2* relaxation correlation measurements in solid-like materials with non-exponential decays

Abstract

Magnetic resonance T1–T2* relaxation correlation is a newly emerging and powerful tool to study the structure and dynamics of materials. However, the T1–T2* of solid-like materials may consist of a linear combination of exponential decays and non-exponential decays, and the traditional methods for processing T1–T2 data would be not applicable. In this paper, a method of processing T1–T2* data with non-exponential decays was proposed. The critical idea is to decompose the data into two sub-datasets, exponential decays and non-exponential decays, employing a non-linear fitting method, and then to invert the sub-datasets and to combine the inversion results. We also introduce a related relaxation correlation measurement, T1ρ–T2*, for examination of solid-like materials. The same data processing strategy as for T1–T2* was implemented. The effectiveness of the proposed method for processing non-exponential data, Sinc Gaussian and Gaussian decay, was validated with simulation and experiment. The results showed that the proposed method recovers T1–T2* and T1ρ–T2* spectra with accurate relative signal intensities. The proposed method provides a platform for further development of MR methods applied to solid-like materials. These relaxation correlations are well suited to measuring composition of mixtures, with solid components in the mixture.