Comparison of Rapid Arc and Intensity Modulated Radiotherapy in a True Beam Linear Accelerator for 6 MV: Application of AAPM TG-119 tests in treatment planning and quality assurance.

OBJECTIVE

We developed rapid arc (RA) and intensity-modulated radiotherapy (IMRT) plans based on the American Association of Physicists in Medicine Task Group-119 (AAPM TG-119) proposals and compared the planning and quality assurance results.

MATERIALS AND METHODS

Two treatment plans were used for each study patient: one using 7-9 IMRT fields and the other using the two full-arc RA methods. Plan optimization and dose calculations were performed using 6 MV photons and Eclipse with the anisotropic analytical algorithm (AAA). Task group (TG)-119 described the planning objectives used to evaluate the treatment plans generated for this study. Point dose, planar fluence measurement, and trajectory log file analysis are used for quality assurance.

RESULTS

The conformity index (CI) for treatment plans varied between 0.76-0.91 when using IMRT and 0.75-0.93 when using RA. The homogeneity index (HI) was approximately 0.10-0.24 (IMRT) and 0.07-0.23 (RA). The ratio of the total number of monitor units required for IMRT to that required for RA was between 0.87 and 2.14. The treatment log files exhibited higher gamma passing with RA than with IMRT.

CONCLUSION

RA plans were more effective than IMRT plans in achieving the test goals. Point dose measurements and electronic portal imaging device (EPID)-based planar fluence measurements showed statistically insignificant differences between the IMRT and RA plan quality assurance (QA) results. However, the trajectory log file analysis exhibited better gamma-passing results for RA than for IMRT.