A fusion of in vivo Neutron and X-ray Computed Tomography to understand water dynamics in biological systems

The interactions between plant roots and soil are an area of active research, particularly in terms of water and nutrient uptake. Since non-invasive, in vivo studies are required, tomographic imaging app ears an obvious method to use, but no one imaging modality is well suited to capture the complete system. X-ray imaging gives clear insight to soil structure and composition, however water is comparatively transparent to X-rays and biological matter also displays p o or contrast. Neutron imaging presents a complementary view where water and biological matter are better distinguished but the soil minerals are not imaged as clearly as they would be with X-rays. This work aims to develop robust methods for complementary X-ray/neutron tomographic imaging of plant root samples which should lead to new insight into water trans- p ort in soil. The key challenges of this project are to develop experiments that will meet the requirements of both imaging modalities and the biological requirements of the plant samples and to develop ways to register a pair of reconstructed volume images of a sample that will typically have been produced with entirely separate facilities. The use of cadmiumducial markers for point-based registration has been investigated to address the registration challenge. Simulations were conducted to investigate the expected registration accuracy as the quantity and distribution of the markers varied. The findings of these simulations were then tested experimentally as plant samples were grown and imaged using neutrons with the IMAT instrument at ISIS Neutron and Muon Source and with X-rays at -VIS X-ray Imaging Centre at the University of Southampton.