Gamma-ray computed tomography (CT) technique for tree stem investigation

Trees have an important role in human life. Trees can improve air quality, stabilize ambient temperature, and so on. Nowadays there have been several incidents of fallen trees and resulted in fatalities. The tree stem investigation was done by gamma ray computed tomography (CT) technique to study the inside condition of the stem. The stem was scanned using the first generation of tomography called parallel beam scanning method. 80 mCi of ¹³⁷Cs emitted gamma photons that penetrated the stem and received by the NaI(Tl) scintillation detector on the other side. Both gamma radiation source and detector were collimated using lead with 5 mm diameter of slits. There were 128 projections data which then reconstructed into image. It took about 522 minutes to collect the 128 projections data. The reconstructed image clearly showed there were density variations and two holes in the stem. Gamma-ray CT looks to be one of promising tree investigation technique. Further development is needed to reduce the scanning time and improve the image quality. (author)