A basic and clinical study of radiosurgery using the linear accelerator (Linac) system for unremovable deep-seated brain tumors is reported. A Komai stereotactic ring was used to locate the target coordinates. The patient was laid on the Linac treatment table and held in the head fixation system. Irradiation was given in five positions. The dose profile by film dosimetry and Rando phantom was s...

Vero4DRT is an innovative image-guided radiotherapy system employing a C-band X-ray head with gimbal mechanics. The purposes of this study were to propose specific MC models of the linac head and multileaf collimator (MLC) for the Vero4DRT and to verify their accuracy. For a 6 MV photon beam delivered by the Vero4DRT, a simulation code was implemented using EGSnrc. The linac head model and the ...

PURPOSE The magnetic fields of linac-MR systems modify the path of contaminant electrons in photon beams, which alters patient skin dose. To accurately quantify the magnitude of changes in skin dose, the authors use Monte Carlo calculations that incorporate realistic 3D magnetic field models of longitudinal and transverse linac-MR systems. METHODS Finite element method (FEM) is used to genera...

PURPOSE A key factor limiting the effectiveness of radiation therapy is normal tissue toxicity, and recent preclinical data have shown that ultra-high dose rate irradiation (>50 Gy/s, "FLASH") potentially mitigates this effect. However, research in this field has been strongly limited by the availability of FLASH irradiators suitable for small animal experiments. We present a simple methodologi...

*Corresponding author: Dr. Asghar Mesbahi, Medical physics department, Medical school, Tabriz university of Medical Sciences, Tabriz, Iran. Fax: +98 411 3364660 E-mail: [email protected] Background: The characteristics of secondary neutrons in a high energy radiation therapy room were studied using the MCNPX Monte Carlo (MC) code. Materials and Methods: Two MC models including a model with...

Introduction: During intensity modulated radiation therapy (IMRT) technique, theoretically, presence of flattening filter (FF) across the beamline of clinical linear accelerator (linac) is not essential to obtain uniform lateral profiles due to intensity modulation of photon beams by multileaf collimators (MLCs). The aim of this study was to investigate the dosimetrical propert...

PURPOSE The distributed computing implementation of the EGSnrc Monte Carlo system using a computer cluster is investigated and tested. METHODS The computational performance was tested for various scenarios with different number of computers used in order to assess the efficiency of the cluster. The presented computation times and efficiencies include the linac head modeling with full simulati...

In this work, soft-tissue equivalence of water, polystyrene, PMMA and water equivalence of polystyrene, and PMMA has been assessed for multiple megavoltage photon beams and field sizes. EGSnrc based Monte Carlo (MC) codes, BEAMnrc and DOSXYZnrc are used for the linac head modeling and the phantom dose calculations, respectively. Percentage depth doses (PDDs) are scored for two field sizes (5 × ...

BACKGROUND The modalities for performing stereotactic radiotherapy (SRT) on the brain include the cone-based linear accelerator (linac), the flattening filter-free (FFF) volumetric modulated arc therapy (VMAT) linac, and tomotherapy. In this study, the cone-based linac, FFF-VMAT linac, and tomotherapy modalities were evaluated by measuring the differences in doses delivered during brain SRT and...

introduction:  skin  sparing  is  one  of  the  most  desirable  characteristics  of  high  energy  photon  beams. however, the photons emerging from the target of linacs are contaminated by secondary  electrons  as  a  result  of  their  interactions  with  air,  collimators,  flattening  filter  and  any  other  objects in their path. this phenomenon tends to increase the skin dose received b...