background: the present work aims to study the out-of-field photon calculation accuracy of a commercial treatment planning system (tps), oncentra, for three-dimensional conformal radiotherapy (3d-crt) and intensity modulated radiation therapy (imrt) treatment techniques from elekta synergy medical linear accelerator. materials and methods: accuracy of individual out-of-field dose components was...

Background: Physical wedges are still widely used as beam modifiers in external beam radiotherapy. However the presence of them in the beam trace may cause beam hardening which may not be considered in many treatment planning systems. The aim of this study is to investigate the beam hardening effect generated by physical wedges via different beam quality indexes as photon spectrum, half value l...

background: during radiotherapy treatment, critical organs are shielded using lead and cerrobend blocks. the objective of this study is to compare the effects of lead and cerrobend shielding blocks on incident photon beam. methods: collimator scatter factors were measured for open square fields (3 x 3 cm to 40 x 40 cm) defined by collimator jaws and for fields blocked down to smaller asymmetric...

Introduction For dose measurement in Megavoltage (MV) photon beams with ion chambers, the effect of volume occupied by the air cavity is not negligible. Therefore, the result of measurement should be corrected with a displacement perturbation correction factor (Pdis) or using an effective point of measurement (EPOM). The aim of this study is to calculate the EPOM for cylindrical ion chamber and...

background: most of the current brachytherapy treatment planning systems (tps) use the tg-43u1 recommendations for dosimetry in water phantom, not considering the heterogeneity effects. objective: the purpose of this study is developing a method for obtaining correction factors for heterogeneity for cs-137 brachytherapy sources based on pre-calculated mc simulations and interpolation. method: t...

Background: Three-dimensional conformal radiotherapy (3D-CRT) and intensity-modulated radiotherapy (IMRT) techniques are used for the treatment of patients with laryngeal cancer. Objective: This study aimed to investigate the effects of these 2 treatment techniques on the planning target volume (PTV) (laryngeal cancer), dose homogeneity, dose of organs at...

Background: In radiation therapy, peripheral dose or the dose outside the radiotherapy field, is important when anatomical structures with very low dose tolerances are involved. One of these critical organs in pelvic irradiation is testis. The amount of radiation delivered to the testes in radiotherapy must be kept as small as possible, consistent with the limit dose of this organ. The threshol...

The treatment couch and some of the positioning devices of patients receiving radiotherapy treatment are made of a material (carbon) which has low attenuation properties for the photon energies used in the radiotherapy. Previous investigations showed the suitability of carbon fiber tabletops in radiotherapy and their very low attenuation properties for a range of X-ray energies and field sizes ...

I discuss mechanisms of heavy quark production in (real) photon-nucleon and (real) photon (real) photon collisions. In particular, I focuse on application of the Saturation Model. In addition to the main dipole-nucleon or dipole-dipole contribution included in recent analyses, I propose how to calculate within the same formalism the hadronic single-resolved contribution to heavy quark productio...

I discuss mechanisms of heavy quark production in (real) photon-nucleon and (real) photon (real) photon collisions. In particular, I focuse on application of the Saturation Model. In addition to the main dipole-nucleon or dipole-dipole contribution included in recent analyses, I propose how to calculate within the same formalism the hadronic single-resolved contribution to heavy quark productio...