Optimisation of Pt sensitivity in PIXE analysis of thin biological samples

To obtain Pt concentration distributions in tumor biopsies, micro-PIXE is used. The Limit of Detection (LOD) for Pt is determined by the background production cross section together with the production cross section for the Pt–L lines. Both are functions of the type and energy of the projectile. In order to optimise the experimental conditions, the proton energy is varied from 2.5 to 5 MeV and the corresponding X-ray spectra are analysed. The optimum LOD is about 1 µg/g for a sample thickness of 1 mg/cm2 and a total charge of 100 µC. A study is performed to investigate the possibility of elemental analysis by means of a excitation. The corresponding LOD is 6 µg/g with 200 µC charge (He++ was used). For a excitation, sample damage limits the beam current and, thus, causes a tremendous increase in the measurement time