Ald. Beckers et al., QUANTITATIVE ELECTRON SPECTROSCOPIC IMAGING IN BIO-MEDICINE - METHODSFOR IMAGE ACQUISITION, CORRECTION AND ANALYSIS, Journal of Microscopy, 174, 1994, pp. 171-182
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.