Investigation of the origin of scatter components transmitted through anti-scatter grids in X-ray Digital Imaging system using Monte Carlo Simulation.

Background: Projection diagnostic X-ray images are inherently affected by the masking effects of transmitted scatter. Spatially distributed transmitted scatter degrades image quality engendering need for effective scatter correction protocol. Objectives: To investigate origin of scatter components transmitted through anti-scatter grids to the detector of digital radiography system using Monte Carlo simulation. Methods: Over 107 photons were exposed through the reconstructed MC simulation phantom. Transmitted photons (primary and scatter) were scored as fluence, dose and deposited energy. Scatter components were investigated analytically over varying phantom thickness, tube kV and grid characteristics. Test disks were exposed as ROI embedded in phantom to evaluate the potential contrast improvement in image quality with the proposed technique. Results: Simulated and experimental results were comparable and in agreement with literature. SPR and SF mean values of 10.5, 0.314 and 7.96, 0.242 through grids of ratio 10:1 and 16:1 respectively was observed. Analysis of scatter components generation in object, grid's assembly, and fluorescent yields gave mean values of 0.815, 0.167 and 0.017, respectively. Image contrast was observed to increase with tube voltage and grid ratio. Conclusion: Achieving better image contrast, reduced patient dose and low scatter transmission while maintaining superior image quality, using grids with high grid ratio and selectivity is recommended.

Diversity and distribution patterns of non-volant small mammals along different elevation gradients on Mt. Kenya, Kenya.

The distribution of small mammals in mountainous environments across different elevations can provide important information on the effects of climate change on the dispersal of species. However, few studies conducted on Afromontane ecosystems have compared the altitudinal patterns of small mammal diversity. We investigated the species diversity and abundance of non-volant small mammals (hereafter 'small mammals') on Mt. Kenya, the second tallest mountain in Africa, using a standard sampling scheme. Nine sampling transects were established at intervals of 200 m on the eastern (Chogoria) and western (Sirimon) slopes. A total of 1 905 individuals representing 25 species of small mammals were trapped after 12 240 trap-nights. Abundance was highest at mid-elevations on both slopes. However, species richness and distribution patterns differed between the two slopes. More species were recorded on Chogoria (24) than on Sirimon (17). On Chogoria, species richness was higher at mid-high elevations, with a peak at mid-elevation (2 800 m a.s.l.), whereas species richness showed little variation on the Sirimon slope. These results indicate that patterns of species diversity can differ between slopes on the same mountain. In addition, we extensively reviewed literature on Mt. Kenya's mammals and compiled a comprehensive checklist of 76 mammalian species. However, additional research is required to improve our understanding of small mammal diversity in mountain habitats in Africa.