Dosimetric validation of Elekta Synergy 6 MV and 10 MV photon beam models in the Monaco

This study assesses and compares the actual beam parameters with those calculated by the treatment planning system (TPS) on the Elekta Synergy linear accelerator at Phuc Thinh General Hospital, Vietnam. Photon beams of 6 MV and 10 MV were analyzed for varying field sizes and depths using a three-dimensional water tank phantom (48 × 48 × 48 cm3) to measure the percentage depth dose (PDD) and profile for open fields (2 × 2 to 40 × 40 cm2) and 60°-wedge fields (5 × 5 to 20 × 20 cm2). Additionally, the same measurement configurations were accurately simulated in the Monaco TPS using a virtual water phantom of dimensions 60 × 40 × 60 cm3. Data were analyzed using the Monaco Commissioning Utility and IBA's MyQA-Accept software. The Gamma index method was set at 3 %/3 mm, 2 %/2 mm, and 1 %/1 mm criteria to compare calculated and measured point doses. For the 6 MV photon, excellent agreement between the measured and calculated PDD and profiles was observed across all field sizes. The gamma passing rates were nearly 100 % when using the 3 %/3 mm and 2 %/2 mm criteria for both the Monte Carlo (MC) and Collapse Cone (CC) algorithms. A similar pattern was observed for the 10 MV photon beam, demonstrating strong agreement in both the PDD and dose profiles with the 3 %/3 mm and 2 %/2 mm criteria using the CC algorithm. However, when applying the more stringent 1 %/1 mm criterion, the small field 2 × 2 cm2 exhibited a significantly lower gamma pass rate and a higher output factor difference compared to the larger field sizes. Despite this, the output factor difference remained consistently below 1.3 % across all energies and field sizes. This study verifies the accuracy of the beam model and dose delivery while highlighting areas for improvement, such as optimizing the multi-leaf collimator (MLC). Continuous validation is recommended to maintain accuracy and treatment quality.