Feature-Specific CT Measurements for Log Scanning: Theory and Application

Computed Tomography (CT) is extensively used as a medical diagnostic tool, and increasingly adopted for scientific and industrial research. In the wood industry, there is a growing interest in using the CT technique to assess the quality of logs entering a sawmill to enable the material to be appropriately processed into maximum value products. Internal features of interest include knots, heartwood/sapwood boundary, rot and splits. Most commercially available CT scanning systems are modeled on medical designs and provide high spatial and density resolution. They are very complex and delicate devices with correspondingly high cost. However, log scanning has its own distinctive characteristics: specific overall and feature geometries and relatively coarse scanning resolution requirement. To fit these characteristics, the novel geometry-based coarse-resolution CT scanning approach described here has been developed and implemented. The models, algorithms, scanner design and result validation are presented in detail. The resulting CT reconstructions for an example log using the proposed geometry-based coarse-resolution approach compare well with CT reconstructions for same log using the same data with conventional filtered back projection inversion. The good comparison gives confidence in the usefulness and applicability of the proposed CT method for industrial use in sawmills for log quality assessment.