Evaluation of VMAT Patient Specific Quality Assurance Using Suncheck on the Halcyon Linear Accelerator
Abstract
Purpose
To evaluate the dosimetric accuracy of SunCHECK, a calculation-based IMRT patient specific quality assurance (PSQA) program, when applied to VMAT PSQA for the Halcyon LINAC.
Methods
Virtual VMAT treatment plans were generated utilizing a Delta4 Phantom+ diode detector array device in order to analyze the accuracy of the dose calculation algorithm in SunCHECK. To analyze the accuracy of the dose calculation algorithm in SunCHECK, two major methods were performed. One approach involved comparing the recalculated dose distribution in SunCHECK (DoseCHECK, PerFRACTION) with the calculated dose distribution from the treatment planning system (TPS) and the other was comparison analysis between the recalculated dose in the SunCHECK (DoseCHECK, PerFRACTION) and the measured dose values by the diode detector array. The characteristics of dose distribution changes calculated by SunCHECK in the event of MLC errors during VMAT beam delivery were analyzed additionally. For this study, a total 20 VMAT plans were prepared. After delivering a beam with MLC position errors, the dosimetric error evaluated through log file-based calculations were compared with the error analysis findings obtained from measurements using the Delta4 Phantom+.
Results
The analysis revealed a strong correlation between the calculated dose in SunCHECK, the planned dose, and the measured delivery dose. The dosimetric error calculated based on the log file using SunCHECK showed a similar trend to the dose error calculated through the conventional measurement-based PSQA method using a Delta4 Phantom+. The average gamma passing rate values for MLC position errors obtained using the Delta4 Phantom+ and SunCHECK systems were 47.6% and 53.2%, respectively, with corresponding standard deviations of 7.77% and 6.18%.
Conclusion
The results of this study validate SunCHECK's accuracy in dose calculation and analysis of dosimetric errors resulting from MLC position errors, thereby confirming its efficacy in VMAT PSQA using the Halcyon LINAC.