HighlightsX-ray CT was effectively used to quantify soil seal/crust thickness.Different micro-morphological zones within seal layers were revealed.Rainfall had a strong and rapid impact on water transport and retention in soil.The existence of a soil-dependent raindrop impact threshold was hypothesized.

Aims Conventional methodology using destructive sampling, which is laborious and has poor spatial and temporal resolution, has limited our understanding of soil-plant interactions. New non-invasive tomographic techniques have the potential to significantly improve our knowledge. In this study we demonstrated the simultaneous use of PET (positron emission tomography) and CT (X-ray computed tomography) to (a) non-destructively image a whole plant growing in sand, and (b) to link the observed morphology with recently assimilated C. The PET scanner was used to detect and visualize the location of the short-lived radioisotope 11 C (with a half-life of 20.4 min) taken up by the plant through 11 C-labelled CO 2 . This provided information on carbon translocation and the metabolism of photo-assimilates in the plant as well as root structure. The CT scanners yielded data on soil and root structure. Methods A medical PET/CT scanner was used to scan a fodder radish plant growing in a pot with test soil composed of homogenous sand. We constructed an air-plant-soil controller system (APS) to control the environmental conditions, such as CO 2 , temperature and light during the experiment. The plant was allowed to assimilate 11 CO 2 for 90 min before PET scanning was initiated. We carried out PET scanning for 60 min. Subsequently, the aerial parts of the plant was cut off and the pot was rescanned using a micro-CT scanner to obtain more detailed information on structure of the root system and the growth medium structure. Results The acquired PET and CT images gave images clearly visualizing the architecture and morphology of root and soil. Using a CT scanner, we were able to detect the main taproot located at 0 to 30 mm depth. With the PET scanner, we were able to measure a signal down to 82 mm below the surface of the sand. We found the highest concentration of 11 C at the position of the main root. The PET images, at different time intervals, showed the translocation and metabolisation of photo-assimilates from top to root. Using the micro-CT scanner (voxel size of 90 μm), we were able to detect roots down to 100 mm depth. These findings correlated the PET signals measured down to 82 mm depth.

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Objective: High-resolution non-invasive three-dimensional (3D) imaging of chondrocytes in articular cartilage remains elusive. The aim of this study was to explore whether laboratory micro-computed tomography (micro-CT) permits imaging cells within articular cartilage. Design: Bovine osteochondral plugs were prepared four ways: in phosphate-buffered saline (PBS) or 70% ethanol (EtOH), both with or without phosphotungstic acid (PTA) staining. Specimens were imaged with micro-CT following two protocols: 1) absorption contrast (AC) imaging 2) propagation phase-contrast (PPC) imaging. All samples were scanned in liquid. The contrast to noise ratio (C/N) of cellular features quantified scan quality and were statistically analysed. Cellular features resolved by micro-CT were validated by standard histology. Results: The highest quality images were obtained using propagation phase-contrast imaging and PTAstaining in 70% EtOH. Cellular features were also visualised when stained in PBS and unstained in EtOH. Under all conditions PPC resulted in greater contrast than AC (p < 0.0001 to p ¼ 0.038). Simultaneous imaging of cartilage and subchondral bone did not impede image quality. Corresponding features were located in both histology and micro-CT and followed the same distribution with similar density and roundness values. Conclusions: Three-dimensional visualisation and quantification of the chondrocyte population within articular cartilage can be achieved across a field of view of several millimetres using laboratory-based micro-CT. The ability to map chondrocytes in 3D opens possibilities for research in fields from skeletal development through to medical device design and treatment of cartilage degeneration.