Improved method based on dual-energy X-ray absorptiometry for nondestructive evaluation of solid wood moisture content.

An accurate, rapid, and convenient method is presented for moisture content (MC) determination of solid wood based on dual-energy X-ray absorptiometry (DXA). Poly(methyl methacrylate)-equivalent thicknesses (PMMA-EThs) of sugi (Cryptomeria japonica D. Don) wood blocks and pure water were measured by means of a wide range of X-ray tube voltages (20-100 kV). The ratio of the PMMA-ETh of pure water to that of wood decreased as X-ray tube voltage was increased, suggesting that an appropriate pair of tube voltages for DXA is 20 and 100 kV. According to this result, X-ray images of 30 wood samples were taken at 20- and 100-kV tube voltages, and their average PMMA-Eths from both images was determined. There was a strong negative correlation between the wetbasis MC of the wood sample and the ratio of its PMMAEth at 100 kV to that at 20 kV. A regression equation was developed for estimating the dry-basis MC of wood samples from their PMMA-ETh ratios. The standard error of estimate was 2.2%, which is better than those determined for electric moisture meters. This approach may lead to the development of a practical, nondestructive moisture meter for wood. [ABSTRACT FROM AUTHOR]