Raster Subject

Often, more detailed information is needed on the distribution of a constituent. The technique of X-ray area scanning, or dot mappings can provide a qualirative view of elemental distributions. As the beam is scanned in a raster pattern on the specimen, a cathode ray rube scanned in synchronism is used to display a full white dot whenever the X-ray detector (WDS or EDS) detects an X ray within a certain narrow energy range. The pattern of dots is recorded on film to produce the dot map. Dot maps are subject to the following limitations ... 

The extent to which it is possible to classify differences between the impact of emissions within one monitoring raster screen, and accordingly to detect heavily loaded areas, will be the subject of further investigation. 

MALDI-MSI has previously been used in combination with whole-body antoradiolnminography (WBAL) to map the distribution of drngs and metabolites in dosed animals (8). The application of MALDI-MSI methods allows for the simnltaneous detection of mnltiple analytes of interest which can be identified by their molecnlar weight and specific fragmentation patterns. Subject to instrumental variance and parameter selection (snch as raster size and spectra acqnisition time and number) whole sections can be imaged rapidly (normally within several honrs for a standard 500 p,m raster) in comparison to WBAL which may require several days. 

---