AbstractID: 7113 Title: Two-stage beam orientation selection method for IMRT
The selection of beam orientations for an IMRT treatment is a difficult and timeconsuming process. Frequently, several trial-and-error attempts are required to obtain an
acceptable set of beam orientations. A full computer optimization of beam profiles and gantry
angles is, in principle, feasible and useful for research purpose. One of the major impediments to
implementing the technique is its excessive computing time. We have developed a two-stage
beam orientation selection method for IMRT planning. At the first stage, the search space is
scanned using a single-beam based ranking function to identify the potentially "good" and "bad"
gantry angles. The "bad" beam directions, from which only a small amount of radiation can be
delivered to the target (e.g., due to the existence of an organ at risk), is then excluded from the
search space. At the second stage, a simulated annealing algorithm is used to search for the best
possible beam configuration in the reduced search space. This approach enables us to
significantly reduce the time required for beam orientation optimization without compromising
the quality of optimization. The two-stage beam orientation optimization algorithm has been
applied to several clinical IMRT treatment cases. Our results indicated that the quality of the
final treatment plan was not affected by the restriction of the search space. At the same time, the
duration of optimization was reduced by a factor of ten or more.