Course book Advanced Treatment Planning 2018

Different plan optimization approaches

• Fluence map optimization (FMO) ➢

Linear relationship between fluence and dose

➢

Less computational effort

➢ Still leaf-sequencing needs to be done either by optimizing MU or aperture • Direct machine parameter optimization (DMPO) ➢ leaf positions and segment weights as variables during optimization ➢ More difficult to solve this problem as more physical constraints exist ➢ Uses simulated annealing, column generation, gradient-based methods or genetic algorithms or heuristic methods • For IMPT FMO is used • Problem is to translate objectives and constraints with non-clinical meaningful weights into objective function → plan quality still depends on time commitment and experience of planer → multi criteria optimization (weight factors avoided)