Inverse Planning - a Comparative Intersystem and Interpatient Constraint Study

Purpose: To compare commercial treatment-planning systems (TPS) for inverse planning (IP) and to assess constraint variations for specific IMRT indications. Material and Methods: For IP,OTP,XiO and BrainSCAN were used and step-and-shoot íntesity-modulated radiotherapy (IMRT) delivery was assumed. Based on identical constraints, IP was performed for a prostate, head and neck, brain, and gynecologic case. IMRT plans were compared n ters of conformity/homogeneity, dose-volume hostograms (DVHs), and delivery efficiency.For ten patients each of a class of indications, constraint variations were evaluated. Results: IMRT plans were comparable concerning munuum target dose, homogeneity, conformity, and masimum doses to organs at risk. Larger differences were seen in dose gradients outside the target dose, monitor units, and segment number. Using help structures proved effcient to shape isodoses and to reduce segmentation workload. For IMRT class solutions, IP constraint variations depended on anatomic site. Conclusion: IP systems requring doses as input and having objective functions based an physichal parameters had a very similar performance. Constraint templates can be established for a class of IMRT indications.