Wood density determination by X- and gamma-ray tomography

Wood density measurement is related to several factors that influence wood quality. In this paper, a CT image calibration procedure which allows image quantification in terms of dry bulk density is presented for three different X- and gamma-ray energies (28.3, and 59.5, and 662.0 keV). The mass attenuation coefficients measured for a set of eight wood species did not vary significantly, allowing a single calibration for determination of bulk density of air-dried wood samples at each energy. The equation for bulk density calibration obtained was validated using a second set of twelve wood species. Comparison of bulk density determined by CT images, using the calibration procedure proposed, with values obtained by gravimetric methods, presented a very good linear correlation coefficient (R-2=0.94). The main advantage of CT imaging over conventional techniques for wood bulk density determination is that it allows detection and quantification of heterogeneities and internal defects. At the sub-millimetric spatial resolution level, it is possible to identify morphological and structural aspects of wood samples.