Transverse NMR relaxation in magnetically heterogeneous media

TL;DR

This paper investigates how heterogeneity in magnetic environments affects NMR transverse relaxation, linking spectral features to spatial frequency correlations, with applications to blood analysis.

Contribution

It introduces a method to relate NMR spectral lineshape to spatial correlation functions of magnetic heterogeneity, enabling quantification of tissue properties.

Findings

Correlation length and Larmor frequency variance can be extracted from NMR spectra.

Numerical simulations support the theoretical model.

Application demonstrated on human blood spectra.

Abstract

We consider the NMR signal from a permeable medium with a heterogeneous Larmor frequency component that varies on a scale comparable to the spin-carrier diffusion length. We focus on the mesoscopic part of the transverse relaxation, that occurs due to dispersion of precession phases of spins accumulated during diffusive motion. By relating the spectral lineshape to correlation functions of the spatially varying Larmor frequency, we demonstrate how the correlation length and the variance of the Larmor frequency distribution can be determined from the NMR spectrum. We corroborate our results by numerical simulations, and apply them to quantify human blood spectra.