Assessment and Evaluation of Dosage Accuracy for Monte Carlo Simulations of the Prowess Panther Radiotherapy Planning System for Head and Neck Cancer

Medical physicists use the treatment planning systems for radiotherapy dose calculations. Every TPS
should be checked for the accuracy of the computed dose compared to dose measured with ion
champers under several cases before it can be used clinically.
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: There was a good agreement of the dose distribution results between TPs and EGS. It
was less than 1% for the dose distribution at PTV and spinal cord and 2.05% for the parotid glands
dose distribution. The calculated dose distribution on Prowess Panther software relatively coincides
with the EGSnrc test program.