1H NMR Relaxation Processes in Lung Tissues at Low Magnetic Fields

TL;DR

This study uses low-field NMR to compare relaxation processes in lung tumor and reference tissues, aiming to identify potential markers for disease detection.

Contribution

The study introduces a novel approach to evaluate lung tissue pathology using low-field NMR relaxation parameters and bi-exponential spin–spin relaxation analysis.

Findings

Spin–spin relaxation in lung tissues showed a bi-exponential behavior, indicating multiple relaxation mechanisms.

Spin–lattice relaxation rates followed a power-law frequency dependence with an exponent of ~0.3, matching reptation dynamics in polymers.

Combined relaxation data analysis identified specific parameters that may serve as markers for pathological tissue changes.

Abstract

Proton spin–lattice and spin–spin NMR relaxation studies were conducted on lung tissue samples from 10 patients. For each case, relaxation properties of tumor tissue were compared with those of the corresponding reference tissue. The spin–lattice relaxation measurements were performed over a wide frequency range, from 10 kHz to 10 MHz, spanning three orders of magnitude. These were complemented by both spin–lattice and spin–spin relaxation data acquired at 18.7 MHz. Notably, the spin–spin relaxation process exhibited a bi-exponential character. This relaxation behavior was quantitatively analyzed using dedicated models to achieve two main goals: to evaluate the diagnostic potential of low-field NMR relaxometry, and to gain insights into the dynamics of water and macromolecules in tissue, in comparison with aqueous solutions of proteins and polymers. The frequency dependence of the spin–lattice relaxation rates was well described by a power-law function, with an exponent of approximately 0.3 closely matching the theoretical prediction for reptation dynamics in polymer systems, associated with the intermolecular relaxation contribution. The combined analysis of spin–lattice and spin–spin relaxation data revealed specific parameters (such as ratios between the relaxation rates or between the amplitudes of individual relaxation components) that can be considered as potential markers of pathological changes affecting molecular dynamics in tissues.

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