Dosimetry study of the Elekta “Synergy S” linear accelerator using measurement and Monte Carlo simulation

Dosimetric parameters of the Elekta “Synergy S”, as a dedicated stereotactic linear accelerator ,have been investigated using measurements and Monte Carlo simulations. “Synergy S” has a unique collimation system and its multileaf collimator (MLC), termed as Beam Modulator (BM), has a maximum opening of 16×21 cm2 and 4 mm leaf width at the isocentre. The high resolution BM, combined with its relatively large maximum field size, makes the opportunity for expanding stereotactic radiation treatment techniques from traditionally smaller targets to larger ones for both cranial and extracranial lesions . Materials and Methods : Synergy S Elekta linac,Ionization chamber(CC13), Kodak X-Omat V films, and Scanditronics Wellhofer water tank were used for the measurements.The Monte Carlo simulation was carried out using code BEAM/EGS4 to model the radiation transport through the “Synergy S” linear accelerator head . Results : Some dosimetric parameters of this linac such as percentage depth doses (PDD), off-axes dose profiles and dose penumbras were measured and calculated for different field sizes and depths . Penumbra widths (80-20%) for this field at isocentre and 10 cm deep were 5.4 and 6.3 mm for the leaf-sides and leaf-ends, respectively. The corresponding values for penumbras %5٠-٩٠and 90-10% were 3.4 and 14.8 mm for the leaf-sides and 4.0 and 16.4 mm for the leaf-ends . Conclusion : In this work the Elekta “Synergy S” linear accelerator and its Beam Modulator MLC system has successfully been modelled for the first time using the Monte Carlo BEAMnrc simulations. Excellent agreements (generally to within 1% or 1mm)for statistics better than 0.5%( 1? level) have been achieved between MC calculation and all measured parameters .

Dosimetry study of the Elekta “Synergy S” linear accelerator using measurement and Monte Carlo simulation Keywords:

radiosurgery , stereotactic , modeling , multileaf collimator , beam modulator