Model based predictive design of post patient collimation for whole body CT scanners

Prakhar Prakash; John Boudry

doi:10.1117/12.2081437

18 March 2015 Model based predictive design of post patient collimation for whole body CT scanners

Prakhar Prakash, John Boudry

Proceedings Volume 9412, Medical Imaging 2015: Physics of Medical Imaging; 941240 (2015) https://doi.org/10.1117/12.2081437
Event: SPIE Medical Imaging, 2015, Orlando, Florida, United States

Abstract

Scatter presents as a significant source of image artifacts in cone beam CT (CBCT) and considerable effort has been devoted to measuring the magnitude and influence of scatter. Scatter management includes both rejection and correction approaches, with anti-scatter grids (ASGs) commonly employed as a scatter rejection strategy. This work employs a Geant4^1,2 driven Monte Carlo model to investigate the impact of different ASG designs on scatter rejection performance across a range of scanner coverage along the patient axis. Scatter rejection is quantified in terms of scatter to primary ratio (SPR). One-dimensional (1D) ASGs (grid septa running parallel to patient axis) are compared across a range of septa height, septa width and septa material. Results indicate for a given septa width and patient coverage, SPR decreases with septa height but demonstrates diminishing returns for larger height values. For shorter septa heights, higher Z materials (e.g., Tungsten) exhibit superior scatter rejection to relatively lower Z materials (e.g., Molybdenum). For taller septa heights, the material difference is not as significant. SPR has a relatively weak dependence on septa width, with thicker septa giving lower SPR values at a given scanner coverage. The results are intended to serve as guide for designing post patient collimation for whole body CT scanners. Since taller grids with high Z materials pose a significant manufacturing cost, it is necessary to evaluate optimal ASG designs to minimize material and machining costs and to meet scatter rejection specifications at given patient coverage.

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Prakhar Prakash and John Boudry "Model based predictive design of post patient collimation for whole body CT scanners", Proc. SPIE 9412, Medical Imaging 2015: Physics of Medical Imaging, 941240 (18 March 2015); https://doi.org/10.1117/12.2081437

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KEYWORDS

Sensors

Tungsten

Signal detection

Scanners

Molybdenum

Monte Carlo methods

Computed tomography

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