Dosimetric parameters calculation for 18 MV photon beam in flattening filter (FF) and flattening filter free (FFF) linear accelerators with and without magnetic deflector and lead filter.

Dosimetric characteristics of the flattening filter (FF) and flattening filter free (FFF) modes of 18 MV therapeutic photon beam were investigated with and without the magnetic deflector (MD) and lead filter. MCNP version 6.1.

Associations between the severity of nasal septal deviation and nasopharynx volume in different ages and sexes: a cone-beam computed tomography study.

Background: Nasal septum deviation (NSD) can cause serious anatomical and clinical complications. It can change the breathing pattern and thus alter the anatomy of the airway structures. Despite its importance, the association between NSD with the nasopharynx volume (NPV) has not been assessed before.

Accuracy Evaluation of EPL and ETAR Algorithms in the Treatment Planning Systems using CIRS Thorax Phantom.

Background: It is recommended for each set of radiation data and algorithm that subtle deliberation is done regarding dose calculation accuracy. Knowing the errors in dose calculation for each treatment plan will result in an accurate estimate of the actual dose achieved by the tumor.

Objective: This study aims to evaluate the equivalent path length (EPL) and equivalent tissue air ratio (ETAR) algorithms in radiation dose calculation.

Investigating the Dosimetric Characteristics of Microbeam Radiation Treatment.

Background: High-radiation therapeutic gain could be achieved by the modern technique of microbeam radiation treatment (MRT). The aim of this study was to investigate the dosimetric properties of MRT.

Methods: The EGSnrc Monte Carlo (MC) code system was used to transport photons and electrons in MRT.

Accuracy of Magnetic Resonance Spectroscopy Techniques in Prostate Cancer and Prostatitis.

Background: Considering the non-invasive nature of magnetic resonance spectroscopy (MRS) and its ability to detect prostate lesions, the present study aimed to investigate the accuracy of MRS techniques in distinguishing between prostate cancer (PCa) and prostatitis.

Methods: Thirty-three patients (18 patients with PCa and 15 patients with prostatitis) were recruited for this study. Magnetic resonance imaging (MRI) and MRS were performed using 1.

Improvement of dose distribution in ocular brachytherapy with I seeds 20-mm COMS plaque followed to loading of choroidal tumor by gold nanoparticles.

Aims And Objectives: Brachytherapy using removable ophthalmic plaques loaded with suitable small sealed radioactive seeds adjacent to the ocular's tumor has been widely used as an effective treatment. The aim of this study was to investigate the dose distribution in a modeled eyeball followed to loading of an ocular melanoma tumor with different concentrations of gold nanoparticles (GNPs) as dose enhancement agent by Monte Carlo (MC) calculations.

Materials And Methods: The MC code of MCNPX 2.

Noninvasive Quantification of Liver Fat Content by Different Gradient Echo Magnetic Resonance Imaging Sequences in Patients with Nonalcoholic Fatty Liver Disease.

Background: Noninvasive quantification of liver fat by gradient echo (GRE) technique is an interesting issue in quantitative magnetic resonance imaging. In this study, the fat content in patients with nonalcoholic fatty liver disease (NAFLD) was quantified with GRE sequences with different and * weighting.

Methods: This prospective, cross-sectional study was performed on thirty NAFLD patients.

Simultaneous characterization of electron density and effective atomic number for radiotherapy planning using stoichiometric calibration method and dual energy algorithms.

Relative electron densities of body tissues (ρ) for radiotherapy treatment planning are normally obtained by CT scanning of tissue substitute materials (TSMs) and producing a Hounsfield Unit-ρ calibration curve. Aiming for more accurate, simultaneous characterization of ρ and effective atomic number (Z) of real tissues, an in-house phantom (including 10 water solutions plus composite cork as TSMs) was constructed and scanned at 4 kVps. Dual-energy algorithms were applied to 80-140 and 100-140 kVp combination scans, for better differentiation of tissues with same attenuation coefficient at 120 kVp but different ρ and Z.

Analytical investigation of magnetic field effects on Proton lateral deflection and penetrating depth in the water phantom: A relativistic approach.

Background: Integrated proton therapy - MRI systems are capable of delivering high doses to the target tissues near sensitive organs and achieve better therapeutic results; however, the applied magnetic field for imaging, influences the protons path, changes the penetration depth and deflects the particles, laterally, leading to dose distribution variations.

Objective: To determine the effects of a magnetic field on the range and the lateral deflection of protons, analytically.

Methods: An analytical survey based on protons energy and range power law relation, without using small angle assumption was done.

Simulation of therapeutic electron beam tracking through a non-uniform magnetic field using finite element method.

Introduction: In radiotherapy, megaelectron volt (MeV) electrons are employed for treatment of superficial cancers. Magnetic fields can be used for deflection and deformation of the electron flow. A magnetic field is composed of non-uniform permanent magnets.

Evaluation of dose enhancement in presence of gold nanoparticles in eye brachytherapy by Pd source.

In recent years, the use of gold nanoparticles in radiation therapy has been introduced as a new approach in radiotherapy. The aim of this study is to investigate the effect of gold nanoparticles (GNPs) in plaque brachytherapy for choroidal melanoma using Monte Carlo (MC) simulation. MCNPX code was used for simulation of human eye, Pd (model 200) brachytherapy source and the 20 mm COMS eye plaque that was loaded with 24 Pd seeds and standardized by Collaborative Ocular Melanoma Study (COMS).

Assessment of two hemispherical and hemispherical-conical miniature sources used in electronic brachytherapy using Monte Carlo Simulation.

Introduction: Since the heart of the electronic brachytherapy system is a tube of a miniature x-ray and due to the increasing use of electronic brachytherapy, there is an urgent need for acquiring knowledge about the X-ray spectrum produced, and distribution of x-ray dose. This study aimed to assess the optimal target thickness (TT), the X-ray source spectrum, and the absorbed dose of two miniature sources of hemispherical and hemispherical-conical used in electronic brachytherapy systems, through a Monte Carlo simulation.

Methods: Considering the advantages of MCNPX Code (2.

Gonad Shielding during Pelvic Radiography: A Systematic Review and Meta-analysis.

Background: Gonad shielding has been extensively advocated during pelvic radiography at or below reproductive ages. The popular practice of gonad shielding is placement of a lead shield in the midline of the pelvis. The aim of this study was to address the prevalence of gonad shielding and find out whether the current practice of gonad shielding can be considered as an effective method to reduce radiation exposure in patients undergoing pelvic radiography.

Dosimetric Characteristics of 6 MV Modified Beams by Physical Wedges of a Siemens Linear Accelerator.

Physical wedges still can be used as missing tissue compensators or filters to alter the shape of isodose curves in a target volume to reach an optimal radiotherapy plan without creating a hotspot. The aim of this study was to investigate the dosimetric properties of physical wedges filters such as off-axis photon fluence, photon spectrum, output factor and half value layer. The photon beam quality of a 6 MV Primus Siemens modified by 150 and 450 physical wedges was studied with BEAMnrc Monte Carlo (MC) code.

Tumor dose enhancement by nanoparticles during high dose rate (192)Ir brachytherapy.

Aims And Objectives: The present study aims to evaluate and compare the dose enhancement factor (DEF) of tumor injected with different nanoparticles (NPs) around high dose rate (HDR) (192)Ir brachytherapy source.

Materials And Methods: Monte Carlo calculations were performed with MCNPX code to determine the DEF caused by in tumor injected with (79)Au, (64)Gd, (26)Fe, and (22)Ti NPs during HDR (192)Ir brachytherapy. The uniform and non-uniform distribution of NPs within tumor was modeled with simple NPs-water mixture, and realistic nano-scale-lattice model.

Analytical Consideration of Surface Dose and Kerma for Megavoltage Photon Beams in Clinical Radiation Therapy.

Background: In radiation therapy, estimation of surface doses is clinically important. This study aimed to obtain an analytical relationship to determine the skin surface dose, kerma and the depth of maximum dose, with energies of 6 and 18 megavoltage (MV).

Materials And Methods: To obtain the dose on the surface of skin, using the relationship between dose and kerma and solving differential equations governing the two quantities, a general relationship of dose changes relative to the depth was obtained.

Monte Carlo estimation of photoneutrons contamination from high-energy X-ray medical accelerators in treatment room and maze: a simplified model.

Despite all advantages associated with high-energy radiotherapy to improve therapeutic gain, the production of photoneutron via interaction of high-energy photons with high atomic number (Z) materials increases undesired dose to the patient and staff. Owing to the limitation and complication of experimental neutron dosimetry in mixed beam environment, including photon and neutron, the Monte Carlo (MC) simulation is a gold standard method for calculation of photoneutron contaminations. On the other hand, the complexity of treatment head makes the MC simulation more difficult and time-consuming.