MICROTOMOGRAPHY WITH IONIZING-RADIATIONS

The physical requirements for tomographic imaging with x-ray photons and energetic ion beams are reviewed and some illustrative applications are briefly described. The number of x-ray photons needed to produce tomographic images of a given quality in terms of spatial and density resolution is shown to be independent of object size. Consequently high resolution microtomography requires very intense sources of photons. The performance of microtomography imaging systems based on synchrotron light sources and microfocus x-ray tubes is intercompared and the latter are found to be surprisingly competitive. For objects smaller than a few hundred microns microtomography with MeV ion beams has been developed in recent years and sub-micron resolution demonstrated. For a given image quality ion beam tomography requires substantially lower fluxes than is the case with photon beams but despite this the absorbed doses are similar, being as high as 10(5) Gy for 1 mu m resolution on a 100 mu m sample.