Multi-institutional study of multileaf collimator parameters and dose calculation accuracy using the enhanced leaf model.

The aim of this study was to determine appropriate multileaf collimator (MLC) parameters for the Enhanced Leaf Model (ELM) for the Varian TrueBeam (120 MLC) and to verify the dose calculation accuracy of the ELM in brain stereotactic radiotherapy (SRT). A survey on transmission and dosimetric leaf gap (DLG) values was conducted at five institutions. Dosimetric verification was performed for brain SRT using SRS MapCHECK or Gafchromic film for four targets (0.4-2.8 cm3) positioned up to 7.6 cm from the isocenter. Median values and 95% confidence intervals for transmission and DLG were established for 6 MV, 10 MV, 6 MV-flattening filter-free (FFF), and 10 MV-FFF beams. Dosimetric verification achieved median gamma passing rates exceeding 95% at 3%/1 mm criterion for all targets. The verification results confirmed that the transmission and DLG values obtained from the survey were clinically acceptable. This study provides useful baseline data for institutions implementing the ELM.