QUANTITATIVE ELECTRON SPECTROSCOPIC IMAGING IN BIO-MEDICINE - METHODSFOR IMAGE ACQUISITION, CORRECTION AND ANALYSIS

Many questions about the metabolism of specific elements in the human body might be answered if elemental concentrations could be measured i n situ in cells. With electron energy-loss spectroscopic imaging (ESI) , concentrations can potentially be determined with high spatial resol ution. The theory of the quantification procedure has already been der ived. Many practical instrument-related problems, however, have to be solved. In the current research an energy-filtering TEM is used and th e image-acquisition chain is examined in detail. Quantification requir es images to be recorded over a large dynamic range. To solve this pro blem, the use of optical attenuation filters has been introduced. The use of the combination of a scintillator screen and a TV-camera as a d etection system has consequences for the processing of the data. Corre ctions for the camera photometric sensitivity and, to some extent, for shading are necessary. Further consequences of such a detection syste m for the correction of the element a-specific spectral background and element detection are discussed. The derived methodology is tested in several ways and finally applied for the quantitative analysis of iro n in liver parenchymal cells of a porphyria cutanea tarda patient.