A COMPARISON OF INTENSITY-MODULATED CONFORMAL THERAPY WITH A CONVENTIONAL EXTERNAL-BEAM STEREOTAXIC RADIOSURGERY SYSTEM FOR THE TREATMENT OF SINGLE AND MULTIPLE INTRACRANIAL LESIONS

Purpose: To compare the stereotactic radiosurgery treatment plans gene rated by a conventional radiosurgery treatment system with the plan ge nerated by a system using intensity modulated beams. Methods and Mater ials: Optimized conformal radiation treatment plans were generated for both single and multiple intracranial lesions using a conventional ra diosurgery treatment-planning system computer and the Peacock treatmen t-planning computer, The Peacock system is a conformal therapy system that uses intensity modulated beams, back projection, and the simulate d annealing optimization technique, The dose delivered to critical str uctures and the target volume were compared by means of dose volume hi stograms between plans generated by the two different systems, The Rad iation Therapy Oncology Group (RTOG) stereotactic radiosurgery criteri a were also used to evaluate each plan. Results: (a) For a single smal l target, radiosurgery plans generated by the conventional radiosurger y system and the Peacock system were comparable, (b) For two separate small targets, where nonoverlapping arcs could be used, plans generate d by the two systems were also comparable, (c) 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 radios urgery system. Conclusions: A treatment plan generated using intensity modulated beams appears to be superior to a multiple isocenter plan u sing a conventional radiosurgery system, for the treatment of a large irregular shaped intracranial target.