IMRT

Because:

• The ‘free fluence’ optimization problem is well behaved. Fast algorithms can be used. • The solution space needs to be explored in an interactive manner. MLC sequencers and precise dose calculation are too slow yet. • e.g. ‘Pareto-optimization/navigation’ currently only works for fluence distributions • It is a long way to go from coarse field shapes to the patient-specific optimum fluence distribution. It is very easy to get trapped in local minima when directly optimizing field shapes - see later. …vs. Direct Aperture Optimization (DAO), Simulated Annealing (Rapid Arc ©)…:

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

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