PURPOSE The aim of this study was to find an optimized configuration of collimator angle, couch angle, and starting tracking phase to improve the delivery performance in terms of MLC position errors, maximal MLC leaf speed, and total beam-on time of DCAT plans with motion tracking (4D DCAT). METHOD AND MATERIALS Nontracking conformal arc plans were first created based on a single phase (maxim...

Multileaf collimator (MLC) is among the radiation field shaping systems used for conformal radiotherapy and intensity modulation radiation therapy techniques. The MLC system that has been designed and fabricated in this study includes 52 leaves, 52 stepper motors, 2 DC motors, 16 programmable logic controllers (PLCs) and one human machine interface (HMI). This system can be mounted on conventio...

PURPOSE The most recent Varian(®) micro multileaf collimator (MLC), the High Definition (HD120) MLC, was modeled using the BEAMNRC Monte Carlo code. This model was incorporated into a Varian medical linear accelerator, for a 6 MV beam, in static and dynamic mode. The model was validated by comparing simulated profiles with measurements. METHODS The Varian(®) Trilogy(®) (2300C/D) accelerator m...

introduction: nowadays new radiochromic films have an essential role in radiotherapy dosimetry. properties such as high sensitivity, good reproducibility, high spatial resolution, easy readout and portability have made them attractive for dosimetry, especially in high-dose-gradient regions. material and methods: in this study, electron-beam dose distributions in homogenous and heterogeneous pha...

Introduction: In electron beam treatment, because of the non-point electron beam source, inverse-square law cannot be applied for dosimetry in different treatment intervals. Therefore, providing source-surface distance (SSD) charts in all clinics is of paramount importance. This study aimed to determine the effective SSD for various electron beam energies and field sizes and to...

The Moduleaf, an add-on miniature multileaf collimator (MMLC) for the Siemens Oncor linear accelerator, provides high resolution field shaping with a maximum inter-leaf leakage dose of 1.50% at 6 MV. However, beyond the maximum treatment field size, the distribution of leakage and scatter along the y axis is different from that of the x axis, with maximum leakage values of 1.53% and 0.39%, resp...

Absolute dosimetry with ionization chambers of the narrow photon fields used in stereotactic techniques and IMRT beamlets is constrained by lack of electron equilibrium in the radiation field. It is questionable that stopping-power ratio in dosimetry protocols, obtained for broad photon beams and quasi-electron equilibrium conditions, can be used in the dosimetry of narrow fields while keeping ...

objective: using megavoltage photons generated by medical linear accelerator is a common modality for the treatment of malignant. the crucial problem for using photon beams >8mv is the photoneutron yields that increase the risk of secondary cancer that treated with high-energy photon beams. the contaminated neutrons produced in different components of the accelerator head and rely on many param...