Gadolinium chloride as a contrast agent for imaging wood composite components by magnetic resonance

Although paramagnetic contrast agents have an established track record in medical uses of magnetic resonance imaging (MRI), only recently has a contrast agent been used for enhancing MRI images of solid wood specimens. Expanding on this concept, wood veneers were treated with a gadolinium-based contrast agent and used in a model system comprising three-ply plywood panels fabricated from two untreated veneers and one treated veneer. The limited degree of effect imparted by the contrast agent for specimens in a water-saturated state likely resulted from contrast agent losses due to leaching during the prerequisite water saturation process. Specimens were also analyzed in the air-dry state using a non-conventional MRI sequence. This allowed what appears to be the first reported visualization of earlywood and latewood bands in MR images for air-dry wood specimens. Observation of significant signal dropout for the gadolinium-treated veneer demonstrated the first successful use of a contrast agent to manipulate the signal intensity of a wood component within a composite structure. This technique shows promise for nondestructive twoand three-dimensional assessments of wood component (e.g., veneers, flakes, particles) distributions and orientations in wood composites.