IMRT

Principles: The optimization problem for the different IMRT techniques

Static gantry, dMLC: (e.g. sliding window)

no distant local minima for `easy’ MLCs,

proven algorithm for solution

Static gantry, step&shoot: local minima possible, but good heuristics for (‘step&shoot’ IMRT) avoiding them (MLC sequencer)

(Notice: algorithm converges, heuristic produces a result)

Rotational-IMRT:

So many local solutions that it becomes impossible to identify the global one, bold heuristics for avoiding the inevitable: getting trapped in a local minimum.

(VMAT, Rapid Arc ©…)

ESTRO IMRT course 2015 IMRT optimization: algorithms&cost functions Brussels October 5th, 2015

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