Exclusive yy -+ hadron pairs are among the most fundamental processes in &CD, providing a detailed examination of Compton scattering in the crossed channel. In the high momentum transfer domain (s, t, large, 19,~ for t/s fixed), these processes can be computed from first principles in &CD, yielding important information on the nature of the QCD coupling a, and the form of hadron distribution am...

background : in spite of clinically useful photon and electron beams, high energy linacs produce secondary particles such as neutrons (photo-neutron production). neutrons have important roles during treatment with high energy photons in terms of protection and dose escalation. in this project, neutron dose equivalent of 18 mv varian accelerators is calculated by tld600 and tld700. materials and...

Studies of photon-photon collisions are reviewed with particular emphasis on new results reported to this conference. These include results on light meson spectroscopy and deep inelastic ey scattering. Considerable work has now been accumulated on resonance production by yy collisions. Preliminary high statistics studies of the photon structure function F$(x,Q2) are given and comments are made ...

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...

Introduction: One of the most effective means for treatment of coronary arteries cramp (CHD) is coronary intravascular Brachiotherapy. In this study, with use of MCNP code, in order to invastigating the score of ditribution of absorbed dose, drope in dose, and simulation mean, radiation doses around iridium_192 radioactive has been done.   Materials and Methods:</str...

Introduction: This study was designed to evaluate dosimetric parameters such as rectal dose, bladder dose, integral dose (ID), homogeneity index (HI) and conformity index (CI) in various treatment plans for prostate cancer. Materials and Methods: Pelvic computed tomography (CT) scans of 27 patients were acquired and transferred to the RTDosePLAN treatment planning system. For each patient, 8 co...

Background: Monte Carlo method (MC) has played an important role in design and optimization of medical linacs head and beam modeling. The purpose of this study was to compare photon beam features of two commercial linacs, Varian 21EX and Elekta SL-25 using MCNP4C MC code. Materials and Methods: The 6MV photon beams of Varian 21EX and Elekta Sl-25 linacs were simulated based on manufacturers pro...

Background: The presence of a wedge filter in the beam trajectory can modify the beam quality and cause some changes in the dosimetry parameters which are usually difficult to be measured directly and accurately. Material and Methods: In this study the MCNP-4C Monte Carlo code was used to simulate the 9 MV photon beam generated by a linear accelerator. Upon getting a good agreement bet...