EVALUATION OF DOSAGE ACCURACY FOR MONTE CARLO SIMULATIONS OF THE PROWESS PANTHER RADIOTHERAPY PLANNING SYSTEM FOR HEAD AND NECK CANCER

Purpose/Object: The purpose of this study was to evaluate the accuracy of the dose distribution of the Prowess Panther radiotherapy planning system for head and neck phantom and patients with nasopharyngeal cancer.

Materials/Methods: Digital imaging and communications in medicine (DICOM) format is the standard for communications between therapeutic and diagnostic modalities. A plan generated by a treatment planning system (TPS) is often exported in DICOM format. The EGSnrc includes BEAMnrc/DOSXYZnrc is a widely used Monte Carlo (MC) package for modelling the Linac head and simulating dose delivery in radiotherapy. It has its own definition of beam orientation, which is not in compliance with the one defined in the DICOM standard. MC dose calculations using information from TPS generated plans require transformation of beam orientations to the DOSXYZnrc coordinate system and the transformation is non-trivial. PTW-Verisoft is a powerful tool in evaluating and verifying the dose accuracy of the radiotherapy planning system.

Results: The dose distribution results of TPS and EGS have good agreement. There were slight differences in the dose distribution on the CT image of the patient (less than 1% for the dose distribution at PTV and spinal cord, and 2.05% for the dose distribution in the parotid glands). This difference had many causes. The main reason was due to humans having made mistakes in the simulation.

Conclusion: The calculated dose distribution on Prowess Panther software relatively coincides with the EGSnrc test program.