Applications of ion-beam tomographic element microanalysis (ITEM)

Developments in tomographic analysis using PIXE are reviewed. Simulated 2D and tomographic analyses show that for a variety of specimens about 20 times more data counts are required for tomographic than for 2D analysis. When shape information available from noise-free STIM tomography is incorporated, this factor is reduced to about 4. Three applications for which ITEM is preferable to 2D analysis are demonstrated. First, ITEM of an ant mandible embedded in amber, a specimen that would be destroyed by sectioning, reveals that zinc is still present and localized. Second, the Ca content of the distal portion of a fruitfly Malpighian tubule is measured with ITEM to be 170 ng. This measurement could not be made using techniques that require sectioning. Finally, ITEM is used to avoid contamination from sectioning in an analysis of Ca in the retina of a fruitfly.