• The goal of radiotherapy is to deliver adequate dose to the tumor and spare the healthy nearest structure
• To achieve this goal, the dose distribution in the treatment area must be calculated accurately.
• The Monte Carlo simulation is a technique that widely accepted as the most accurate method
• In this study we have modeled the Elekta Synergy Linear Accelerator with BEAMnrc and Dose calculation in rectillinear voxel with DOSXYZnrc Monte Carlo Simulation code.

Simulation Phase:

• The vendor provided materials and geometric informations were accurately inputed in BEAMnrc code to build the head.
• Incident mean electron energies and  Field Width Half Maximum (FWHM) from 5.8-6.8 MeV,  0.1 - 0.45 cm were investigated.
• A homogeneous water phantom with dimension of 50 × 50 × 50 cm³ were designed with a grid resolution of 0.5 × 0.5 × 0.2 cm³ for PDD and 0.2 × 0.5 × 0.5 cm³ for Profile for the field sizes of 5 x 5, 10 x 10, and 30 x 30 cm² at the depth of 10 cm with DOSXYZnrc code.
• The 3ddose dose output files of the DOSXYZnrc code were read and analyze by the STATDOSE code.

Measurement Phase:

• The IBA water phantom with dimension of 50x50x50 cm³ and the cc13 ionization chamber were used for all measurements.
• Gamma index method was used to quantifying the simulation and measured distributions.
•  The gamma index verification passing criteria, % Dose Difference and Distance to Agreement were chosen 90%, 3% and 3 mm respectively.

• BEAMnrc and DOSXYZnrc codes are accurately modeled the linac treatment head and phantom.
• The results obtained with this code for different therapeutic depths and field sizes were shown an excellent agreement with measurements.
• So this modeling with validate combination can be used to calculate the dose distribution for real patient and for further studies of medical linac.

• Since Monte Carlo is powerfull tools for accurate dose calculation, So this Monte Carlo Simulation technique could be used as a alternative of seconcd check procedure compare to commercially available calculation algorithm.

• Dr. Md. Abdul Mannan Chowdhury
• Prof. Dr. Golam Abu Zakaria
• Volker Steil, University Medical Center Mannheim
• Professor Dr. Günther Hartmann,Deutsches Krebsforschungszentrum (DKFZ)
• Prof. Dr. Klemens Zink, Technical University of Central Hesse, Germany
• DAAD  (German Academic Exchange Service ) Authority for scholarship
• Elekta Company