Beam placement for head and neck IMRT with bilateral lymph node involvment and contralateral parotid gland sparing

Objective: To determine the optimum beam arrangement for head and neck IMRT with bilateral lymph node involvement and contralateral parotid gland sparing. Material and Methods: A preliminary plan with 18 equidistant coplanar beams was prepared for each patient. Subsequent 5- beam plans were prepared based on the beams that contributed the most dose after the first optimization. This method gives plans with target coverage, dose homogeneity in the target volume, and normal tissue sparing similar to the 18-beam plan. The plan with the optimized beam arrangement was compared with a standard 5-beam equidistant configuration. Results: Preliminary 18-beam plans, optimized 5-beam plans, and equidistant 5-beam plans are presented and evaluated using different methods. Conclusion:^For this treatment site, class solutions for IMRT treatment planning (that include the beam arrangement) are an effective way to reduce the time needed to produce an optimal plan. This method can be used to determine class solutions, or for unusual treatment volumes, to reduce the time required to iteratively search for the optimal beam arrangement.