Micro-computed X-ray tomography: a new non-destructive method of assessing sectional, fly-through and 3D imaging of a soft-bodied marine worm.

The detailed examination of the internal and functional anatomy of soft-bodied marine worms has, until now, only been possible using the time consuming and destructive techniques of dissection, histology and electron microscopy. This is the first description of soft body morphology in polychaetes (Nephtys hombergii) derived by means of a bench-top X-ray micro-CT scanner. The data are augmented, for comparison, by dissections, microscopy and scanning electron microscopy of the same species to show how this non-destructive technique can rapidly and reliably produce high-quality morphological data. It can also be applied to rare or unique invertebrate soft tissue material from museum collections and also to large-scale invertebrate comparative anatomical studies possibly leading to greater evolutionary and taxonomic understanding. High-definition images were obtained without the use of special tissue enhancing stains or radio-opaque fluids and it is believed that this is the first time the technique has been successfully applied to this group of invertebrates. Extrapolation of the sectional imaging of regions of the gut and the production of three-dimensional rotating and 'fly-through' imaging can assist in assessment of aspects of functional anatomy.

Crack initiation processes in acrylic bone cement.

A major constraint in improving the understanding of the micromechanics of the fatigue failure process and, hence, in optimizing bone cement performance is found in the uncertainties associated with monitoring the evolution of the internal defects that are believed to dominate in vivo failure. The present study aimed to synthesize high resolution imaging with complementary damage monitoring/detection techniques. As a result, evidence of the chronology of failure has been obtained. The earliest stages of crack initiation have been captured and it is proposed that, in the presence of a pore, crack initiation may occur away from the pore due to the combined influence of pore morphology and the presence of defects within regions of stress concentration. Furthermore, experimental evidence shows that large agglomerations of BaSO(4) are subject to microcracking during fatigue, although in the majority of cases, these are not the primary cause of failure. It is proposed that cracks may then remain contained within the agglomerations because of the clamping effect of the matrix during volumetric shrinkage upon curing.

Microtomography assessment of failure in acrylic bone cement.

Micromechanical studies of fatigue and fracture processes in acrylic bone cement have been limited to surface examination techniques and indirect signal analysis. Observations may then be mechanically unrepresentative and/or affected by the presence of the free surface. To overcome such limiting factors the present study has utilised synchrotron X-ray microtomography for the observation of internal defects and failure processes that occurred within a commercial bone cement during loading. The high resolution and the edge detection capability (via phase contrast imaging) have enabled clear microstructural imaging of both strongly and weakly absorbing features, with an effective isotropic voxel size of 0.7 microm. Detailed assessment of fatigue damage processes in in vitro fatigue test specimens is also achieved. Present observations confirm a link with macroscopic failure and the presence of larger voids, at which crack initiation may be linked to the mechanical stress concentration set up by adjacent beads at pore surfaces. This study does not particularly support the suggested propensity for failure to occur via the inter-bead matrix; however crack deflections at matrix/bead interfaces and the incidence of crack arrest within beads do imply locally increased resistance to failure and potential improvements in global crack growth resistance via crack tip shielding.