Advanced Physics for Brachytherapy 2018

1. I need to be efficient, spatial discretization

For spatial discretization, Acuros partitions the computational volume (the CT image series) into variable sized Cartesian elements. Computational element size varies based on material properties and the gradient of the scatter photon fluence . The spatial derivatives in the LBTEs are replaced by finite differences at multiple points within each computational element Supplementary equations are used to describe fluence variation between these points and preserve particle balance (DFEM - linear discontinuous Galerkin finite-element method) Hence the angular fluence is known everywhere in each element, not only at the points where spatial derivatives are evaluated BUT spatial discretization errors can ensue at points in high fluence gradients

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