Proton nuclear magnetic resonance studies on brain edema

TLDR

In normal rat brain, T1 and T2 relaxation times are single components and shorter than in pure water. The study used pulse NMR to measure longitudinal (T1) and transverse (T2) relaxation times in normal and edematous rat brain tissues. T2 relaxation in edematous rat brain separates into fast and slow components, with T1 prolongation indicating increased water volume, and the slow T2 phase shows steady edema fluid accumulation in TET‑induced edema while cold injury first increases water‑rich fluid and then protein‑rich fluid, demonstrating that proton NMR relaxation times can differentiate edema types and dynamics.

Abstract

The water in normal and edematous brain tissues of rats was studied by the pulse nuclear magnetic resonance (NMR) technique, measuring the longitudinal relaxation time (T1) and the transverse relaxation time (T2). In the normal brain, T1 and T2 were single components, both shorter than in pure water. Prolongation and separation of T2 into two components, one fast and one slow, were the characteristic findings in brain edema induced by both cold injury and triethyl tin (TET), although some differences between the two types of edema existed in the content of the lesion and in the degree of changes in T1 and T2 values. Quantitative analysis of T1 and T2 values in their time course relating to water content demonstrated that prolongation of T1 referred to the volume of increased water in tissues examined, and that two phases of T2 reflected the distribution and the content of the edema fluid. From the analysis of the slow component of T2 versus water content during edema formation, it was demonstrated that the increase in edema fluid was steady, and its content was constant during formation of TET-induced edema. On the contrary, during the formation of cold-injury edema, water-rich edema fluid increased during the initial few hours, and protein-rich edema fluid increased thereafter. It was concluded that proton NMR relaxation time measurements may provide new understanding in the field of brain edema research.