Ald. Beckers et al., QUANTITATIVE ELECTRON SPECTROSCOPIC IMAGING IN BIO-MEDICINE - EVALUATION AND APPLICATION, Journal of Microscopy, 183, 1996, pp. 78-88
Electron spectroscopic imaging (ESI) with the energy-filtering transmi
ssion electron microscope enables the investigation of chemical elemen
ts in ultrathin biological sections. An analysis technique has been de
veloped to calculate elemental maps and quantitative distributions fro
m ESI sequences. Extensive experience has been obtained with a practic
al implementation of this technique. A procedure for more robust eleme
nt detection has been investigated and optimized. With the use of Fe-l
oaded Chelex beads, the measurement system has been evaluated with res
pect to the linearity of the element concentration scale, the reproduc
tibility of the measurements and the visual usage of images results. I
n liver specimens of a patient with an iron storage disease the detect
ability of iron was tested and we tried to characterize iron-contained
components. The concentration measurement scale is approximately line
ar up to a relative section thickness of approximate to 0.5. Monitorin
g of this parameter is therefore considered to be important. The repro
ducibility was measured in an experiment with Fe-Chelex. The iron conc
entration differed by 6.4% between two serial measurements. Element di
stributions are in many applications interpreted visually. For this pu
rpose the frequently used net-intensity distributions are regarded as
unsuitable. For the quantification and visual interpretation of concen
tration differences mass thickness correction has to be performed. By
contrast, for the detection of elements the signal-to-noise ratio is t
he appropriate criterion. Application of ESI analysis demonstrated the
quantitative chemical capabilities of this technique in the investiga
tion of iron storage diseases. Based on an assumed ferritin iron loadi
ng in vivo, different iron components can be discerned in liver parenc
hymal cells of an iron-overloaded patient.