AbstractID: 7991 Title: Peregrine as a Verification Tool of Corvus Treatment Planning System Introduction: With the dramatic increase in computer speed in recent years, Monte Carlo simulation has found its increasing applications in daily clinical dose calculation. We evaluated a Monte Carlo simulation-based treatment planning system (TPS), Peregrine# (version 1.2), as a verification tool for a finite-size pencil beam algorithm-based TPS, Corvus$, when they are applied to MIMiC$ collimators. Material and Methods: Radiation treatment plan is created using the conventional Corvus TPS. Beam and patient (or phantom) data are then sent to the Monte Carlo simulation-based TPS, and dose distribution is regenerated. Measurement is done using radiographic films and ionization chambers for comparison with the output from Corvus and Peregrine. Three categories of targets are selected for comparison. They are targets within buildup tissues, near metallic implant, or in the buildup region. Results: For the target well within buildup tissues, we have not yet observed more than 3% difference between doses predicted by Corvus and Peregrine. For the target near metallic implant, the difference can be as large as 7%. In our phantom study, the target partially lies in a buildup region (adjacent to a large air cavity), doses predicted by Corvus and Peregrine differ by 10%. Measurements using radiographic film agree with the prediction by Peregrine within 3% for this phantom study, indicating Peregrine complements Corvus which can not accurately model the buildup region. # Registered trade mark of Lawrence Livermore National Laboratory and licensed exclusively to NOMOS Corporation for commercial use. $ Registered trade mark of NOMOS Corporation