This study aims to compare the dosimetric accuracy between the enhanced leaf model (ELM) in Eclipse V18.0 and the traditional multileaf collimators (MLCs) modelling in Eclipse V16.1 for volumetric modulated arc therapy (VMAT) and stereotactic body radiotherapy (SBRT) treatments. The objective is to evaluate whether the ELM improves dose calculation accuracy and agreement with measurements in clinical practice.

A retrospective analysis of 30 patients was conducted, categorized into Head-and-Neck (H&N), pelvic and lung SBRT groups. Treatment plans were created using the Acuros XB algorithm in both Eclipse versions. Gamma index pass rates for 1%/1 mm, 2%/2 mm and 3%/3 mm criteria were calculated using portal dosimetry for patient-specific quality assurance. Validation of MLC modelling was performed using closed leaf fields, sweeping gap fields, and the Picket Fence (PF) test across 6MV, 10MV, 6FFF and 10FFF photon energies.

Eclipse V18.0 demonstrated statistically significant improvements (p < 0·05) in dosimetric accuracy and gamma index pass rates across all photon energies and test conditions. In fully blocked fields, dose discrepancies reduced from 1.1% in V16.1 to 0.49% in V18 for 6MV. For the 6 mm sweeping gap test, discrepancies reduced from 1.19% to 0.31% for 6MV. The 1%/1mm gamma pass rates improved from 70% to 91.8% for H&N cases and from 82.4% to 87.3% for SBRT cases.

The ELM in Eclipse V18.0 significantly improves dose calculation accuracy and treatment deliverability, supporting its adoption in clinical practice for VMAT and SBRT to achieve better treatment accuracy and outcome.