IMRT

Kernel-based methods: 2D-superposition methods: Pencil Kernel algorithms

As for 3D point kernel methods, the superposition integral is a convolution integral, if the pencil kernel in spatially invariant ( homogeneous media )

→ very fast dose calculation using Fast Fourier Transformation

Approximate methods to handle inhomogeneous media: • density corrections: mainly effective pathlength rescaling along beam direction • simplified modelling of phantom scatter: local lateral scatter effects not modelled correctly • neglect energy spectrum changes • simplified modelling of head scatter: requires correction factors for the output-factor …and approximations to the head model approx. dose deposition in the patient

ESTRO IMRT course 2015 Dose Calculation in Static and Rotational IMRT Brussels October 8th, 2015

-37-