A comparison of intensity modulated conformal therapy with a conventional external beam stereotactic radiosurgery system for the treatment of single and multiple intracranial lesions

Purpose: To compare the stereotactic radiosurgery treatment plans generated by a conventional radiosurgery treatment system with the plan generated by a system using intensity modulated beams. Methods and Materials: Optimized conformal radiation treatment plans were generated for both single and multiple intracranial lesions using a conventional radiosurgery treatment-planning system computer and the Peacock treatment-planning computer. The Peacock system is a conformal therapy system that uses intensity modulated beams, back projection, and the simulated annealing optimization technique. The dose delivered to critical structures and the target volume were compared by means of close volume histograms between plans generated by the two different systems. The Radiation Therapy Oncology Group (RTOG) stereotactic radiosurgery criteria were also used to evaluate each plan. Results: (a) For a single small target, radiosurgery plans generated by the conventional radiosurgery system and the Peacock system were comparable. (b) For two separate small targets, where nonoverlapping arcs could be used, plans generated by the two systems were also comparable. (e) For a single large (>4 cm) irregular-shaped target, the Peacock system appeared to be able to generate a treatment plan superior to that of the conventional radiosurgery system. Conclusions: A treatment plan generated using intensity modulated beams appears to be superior to a multiple isocenter plan using a conventional radiosurgery system, for the treatment of a large irregular shaped intracranial target.