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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 radiographysystem 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. 
Keywords: Monte Carlo simulation; Anti-scatter grids; image quality assessment; scatter correction.