Poster - Thur Eve - 73: Dosimetric Performance of Radionics Mini-MLC on Elekta Synergy S Linear Accelerator: A Monte Carlo Evaluation

Abstract

This work contributed new information of dosimetric evaluation of Radionics mini-multileaf collimator (MMLC) attached on the head of an Elekta Synergy S linear accelerator using Monte Carlo simulations. The penumbrae, depth and lateral dose profiles of the Radionics MMLC for the 6 MV photon beams, were determined first time using the EGSnrc-based Monte Carlo codes (BEAMnrc) verified by measurements. The Monte Carlo modelled MMLC has a maximum field size of 9.6 × 12 cm2 and 3.8 mm leaf thickness at the isocenter. Monte Carlo verification was carried out using CC13 Wellhofer ionization chamber (cavity volume = 0.13 cm3) and a Wellhofer water tank for measurements. Dosimetric parameters such as the penumbrae, percentage depth doses, the in-plane and cross-plane off-axis dose profiles were measured and calculated for different field sizes and depths. Penumbra widths (80%−20%) for the reference field of 9.6 × 10.4 cm2 at the isocenter with a depth of 10 cm were 4.8 and 5.1 mm for the leaf-sides and leaf-ends, respectively. The corresponding values of penumbrae at depths of 1.5 and 5 cm were 3.6 and 4.2 mm for the leaf-sides and 3.8 and 4.5 mm for the leaf-ends. Dosimetric results based on our Monte Carlo model demonstrated excellent agreement to within 1% or 1 mm when compared to measurements. Our Monte Carlo model for the MMLC is expected to benefit the commissioning of the stereotactic radiosurgery planning for the small intracranial and extracranial lesions.