Submicrometer structure of sea urchin tooth via remote synchrotron microCT imaging

Remote electron microscopy sessions are featured at a number of imaging centers. Similarly, many synchrotron light sources offer routine "mail-in" crystallography and powder diffractometry. At imaging beam lines, small numbers of (preliminary) scans are sometimes performed by staff, in the absence of the investigator, to demonstrate feasibility of the proposed study or as an industrial service. In the 1990s, one of us (SRS) participated in processing experiments where samples were couriered between Georgia Tech and SSRL and synchrotron microCT followed the spatial distribution of densification. Here, the authors report results of remote microCT experiments, i.e., where the investigator who knows the sample interacts via the web with the beam line scientist operating the apparatus and provides real-time feedback on where to scan based upon radiographs and on the most recent reconstructions. Local tomography imaged sea urchin teeth with 350 nm isotropic volume element (voxel) at beam line ID-19, ESRF. Sea urchin teeth form by growing parallel plates of high Mg calcite, each of which is 2-5 μm away from its neighbors, and very high Mg calcite columns later link the plates. The remote imaging session focused on tooth positions where the columns were just forming, and column shapes and dimensions were measured, something which has previously only been done with destructive sample preparation and scanning electron microscopy. The experiments were successful despite a separation of 4,400 miles and seven time zones.