IMRT 2018

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 is spatially invariant ( homogeneous media )

→ very fast dose calculation using Fast Fourier Transformation

approx. dose deposition in the patient

Approximate methods to handle inhomogeneous media:

• density corrections: mainly effective path length 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

ESTRO IMRT course 2017 Dose Calculation in Static and Rotational IMRT Madrid April 13th, 2017

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