Forest Investment Account (FIA) - Forest Science Program
FIA Project Y051244

    Modelling subalpine Fir trees using industrial computed tomography (CT) imaging and simulated X-ray scanning
Author: Alkan, Sencer
Imprint: B.C. : Forintek Canada Corp., 2005
Subject: Forest Investment Account (FIA), Logs, British Columbia, Stems (Botany)
Series: Forest Investment Account (FIA) - Forest Science Program
The growing pressure from steadily rising timber costs and declining wood supply make it essential that application of internal log scanning technologies be actively pursued to maximize use of underutilized timber resources, such as subalpine fir. Two main needs must be satisfied for effective integration and efficient utilization of subalpine fir stems/logs. First, development of a tree model using data obtained from an internal log scanning method that can describe every log and stem by its properties in detail for research purposes. Second, as optimized utilization of the raw material in a sawmill requires knowledge of the properties of the individual logs, it is also necessary to assess feasibility of integrating new equipment for scanning the interior of logs that enable measuring internal properties of logs and stems with acceptable levels of speed and accuracy. This report describes the design and implementation of a new surface-volume integrated tree stem model, CTSTEM, for measuring and visualization of three-dimensional (3D) properties of subalpine fir stems from X-ray images based on various projections. CTSTEM has two main components. Using full scale X-ray projection (CT) data, the first component of CTSTEM represents a subalpine fir tree stem using five modelling units, which closely resemble the real stem structure of the trees: shape, sapwood boundary, knots, branch segment, and wetwood. Design of this component consists of two primary phases. First phase comprises of the segmentation of a single CT image slice, which results in the extraction of 2D defect-like regions. The second phase comprises of the correlation of the 2D defect-like regions across CT image slices in order to establish three-dimensional (3D) support. The 2D defect-like regions with adequate 3D support are labelled as true defects. The 3D reconstruction and visualization of the modeling units is based on the volume-surface-integrated modeling concepts. The 3D output of the model agrees with manually measured properties. The second component of CTSTEM represents logs based on parameterization (simulation of signals) of the CT images based on fan-beam and cone beam geometry. The basic idea is based on the principles of CT, with the exception that only three fan-beam and cone-beam projections are used. The aim was to simulate principles of industrial X-ray Log Scanner based on three fixed and cone-beam X-ray sources. Using the simulated signals, the component creates x-ray images of the modeling components logs. Exact reconstructions of the internal components from three projections were not possible. However, good estimates for the size and co-ordinates of the knot and wetwood patterns were achieved with the method. The most important conclusions of this project were that: CT scanning is a powerful research tool for acquiring data for the modelling and visualization of different stem properties of subalpine fir species. CTSTEM is capable of automatic detection, 3D modeling, visualization and calculation of parameters of the subalpine fir modelling units. It provides a synergistic analysis capability for quantitative and qualitative evaluation of the modeling units (objects) by enabling 3D virtual models of the structures that cannot otherwise be seen, or seen in sufficient detail. As a proof of concept, simulation of the X-ray Log Scanners based on the parameterization of the CT is very promising as a suitable technique for imaging internal features in green subalpine fir logs. Due to limited sample size used in this study, while the results of CTSTEM are currently not intended to be part of industrial applications, it is a demonstration research tool that can illustrate potential benefits of modeling and simulation, based on CT scan data, to the Canadian forest product industry. CTSTEM provides means towards better utilization of the non-traditional subalpine fir species, which is essential for successful sustainable forest management in B.C.
Sencer Alkan.


Modelling Report (1.5Mb)

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Updated August 16, 2010 

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