MR Study of Water Distribution in a Beech (Fagus sylvatica) Branch Using Relaxometry Methods

Abstract

Wood is a widely used material because it is environmentally sustainable, renewable and relatively inexpensive. Due to the hygroscopic nature of wood, its physical and mechanical properties as well as the susceptibility to fungal decay are strongly influenced by its moisture content, constantly changing in the course of everyday use. Therefore, the understanding of the water state (free or bound) and its distribution at different moisture contents is of great importance. In this study, changes of the water state and its distribution in a beech sample while drying from the green (fresh cut) to the absolutely dry state were monitored by 1D and 2D 1H NMR relaxometry as well as by spatial mapping of the relaxation times T1 and T2. The relaxometry results are consistent with the model of homogeneously emptying pores in the bioporous system with connected pores. This was also confirmed by the relaxation time mapping results which revealed the moisture transport in the course of drying from an axially oriented early- and latewood system to radial rays through which it evaporates from the branch. The results of this study confirmed that MRI is an efficient tool to study the pathways of water transport in wood in the course of drying and is capable of determining the state of water and its distribution in wood.

A Multi-Parametric Investigation on Waterlogged Wood Using a Magnetic Resonance Imaging Clinical Scanner

“…For this reason, the T 2 * relaxation times are much shorter than those of the free water in the vessels [39,52]. Indeed, T 2 * measured in wood at RH = 30% belongs to water molecules bound to the wood polymers present in the cell wall, and therefore, it can be used to extract information on the wood density since it depends on the overall lumen volume and cell wall volume fractions [52,61].…”

Influence of Mechanical Wounding and Compartmentalization Mechanism on the Suppression of Invasive Plant Species Using the Example of Cherry Laurel (Prunus laurocerasus)

“…Due to its structure and high moisture content, wood is a convenient material for studying of changes in moisture distribution after injury by MRI. With suitably selected MRI parameters the MR signal obtained from the observed wood tissue is directly proportional to the amount and distribution of water [29][30][31][32].…”

“…A 2D multi-slice spin-echo MRM sequence was used with the following parameters: field of view (FOV) -60 x 30 mm 2 , echo time (TE) -10,4 ms; repetition time (TR) -187 ms, imaging matrix -512 × 256, in plane resolution -117 µm isotropic and, slice thickness -1 mm, number of slices -16 (no gap was between the slices), slice orientation was longitudinal with respect to the sample, two signal averages were used and total MR imaging time was 25 min and 33 sec. The parameters of MRI were optimized for fast acquisition and to gain a signal proportional to the water content in wood [30,33].…”

Two-step diffusion in cellular hygroscopic (vascular plant-like) materials

“…Water transport (drying, absorption, and sap flow) is fundamental in the life or use of natural materials such as plants, trees, wood, vegetables, fruits, seeds, etc. Most of these systems are made of a cellular hygroscopic structure containing water molecules with different mobilities as observed by nuclear magnetic resonance (NMR) relaxometry (1)(2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12). Typically, free water is contained in cavities several orders of magnitude larger than the molecular scale, while bound water is set through hydrogen bonds between lignocellulosic macromolecules.…”