On-line elemental mapping in biomedical research

Abstract

In biomedical research, elemental maps give valuable information about the role of elements in the aetiology of many diseases. For creating such elemental maps we use a scanning proton microprobe set-up to perform Particle Induced X-ray Emission (PIXE), Nuclear Backscattering Spectroscopy (NBS) and Nuclear Forward Scattering Spectroscopy (NFS) experiments simultaneously, preceded by a Scanning Transmission Ion Microscopy (STIM) experiment to localise the area of interest. PIXE is used to detect trace elements and NBS/NFS or STIM is used to determine local areal mass densities. Transferring experimental list-mode data into the thick target corrected concentration distributions is a time-consuming process. However, it would be advantageous to display continuously updated elemental maps as the data accumulate. This paper introduces a data processing method for use in biomedical research, based on dynamic analysis. For calculating concentrations, dynamic analysis uses a matrix transform technique instead of the nonlinear least squares fitting procedures in conventional methods. Applying dynamic analysis reduces the processing time from several hours to less than 1 min. The matrix correction factors for use in thick target corrections, are calculated using the local areal mass densities. The over all time reduction of this method is sufficient to calculate the intermediate, peak overlap resolved, background subtracted and thick target corrected concentration distributions while the data acquisition system is gathering a new subset of data.