Line trajectory X-ray tomography for dendrochronology of large wooden objects

Abstract. Computational Tomography (CT) is a powerful non-invasive 3D imaging technique for cultural heritage research, as the interior of art-historical objects can be investigated by virtually slicing through the object. An application is dendrochronology (i.e. tree-ring research), in which wooden objects are dated by measuring their tree rings and comparing this series with reference chronologies anchored in time. The more tree rings in a series, the higher the chances to obtain a date. Tree rings are not always accessible for measuring on the transverse surface of art-historical objects such as panel paintings and sculptures. In these cases, CT imaging can provide access to the internal tree rings patterns. Most art-historical wooden objects are too large to fit or fully rotate in a medical or lab-based CT scanner. However, for dendrochronological research only one (virtual) cut through the wood is needed, not a full 3D reconstruction. Here we propose a novel line trajectory scan, in which the object is moved sideways between source and detector and very limited angle data is collected. By choosing the orientation of the tree rings approximately parallel to the source-detector axis, they can be visualised sharply in one slice using an iterative reconstruction method. We will demonstrate both the data collection method and the associated algorithms for tomography-based dendrochronology of large wooden objects with the line trajectory scan.