Occupational external exposure to ionizing radiation in research-associated activities in Iran (2015-2020).

Research is an integral part of radiological and nuclear activities; thus, workers may receive different levels of occupational exposure. In the present study, occupational external exposure of workers was studied at the largest radiological and nuclear research institute of Iran from 2015-2020. The activities included research reactors, nuclear fuel cycle, development on radiopharmaceuticals and radioisotopes, particle accelerators, plasma and fusion, and nuclear agriculture.

COMPARISON OF CBCT AND CT IN TERMS OF DOSE VALUE OF ORGANS AT RISK IN PARANASAL SINUS IMAGING.

Irradiated dose to the organs at risk surrounding the paranasal sinuses was compared in cone beam computed tomography (CBCT) and multi spiral computed tomography with respect to the organs' relative positions to the imaging field. A head and neck Alderson-Rando phantom equipped with thermoluminescence dosemeters pellets was irradiated according to three routine CBCT protocols and one protocol in multi spiral computed tomography. Dose value of organs outside the imaging field as well as those measured dose of organs inside the field were assessed.

Effect of annealing temperature and dopant concentration on the thermoluminescence sensitivity in LiF:Mg,Cu,Ag material.

LiF:Mg,Cu,Ag is a new dosimetry material that is similar to LiF:Mg,Cu,P in terms of dosimetric properties. The effect of the annealing temperature in the range of 200 to 350°C on the thermoluminescence (TL) sensitivity and the glow curve structure of this material at different concentrations of silver (Ag) was investigated. It has been demonstrated that the optimum values of the annealing temperature and the Ag concentration are 240°C and 0.

Evaluation of the radiation dose in the thyroid gland using different protective collars in panoramic imaging.

Background: The value for the use of thyroid shield is one of the issues in radiation protection of patients in dental panoramic imaging.

Objectives: The objective of this research is to investigate the attenuation characteristics of some models of thyroid shielding in dental panoramic examinations.

Methods: The effects of five different types of lead and lead-free (Pb-equivalent) shields on dose reduction of thyroid gland were investigated using implanted Thermoluminescence Dosemeters (TLDs) in head-neck parts of a Rando phantom.

DOSIMETRIC ASPECTS OF OPTIMIZATION OF PROTECTION IN IRAN INDUSTRIAL RADIOGRAPHY PRACTICE.

According to the worldwide reports, industrial radiography is one of the highest risk radiation practices due to handling high activity sources. Therefore, an optimization of protection along with appropriate investigation level and/or dose constraint is required to achieve appropriate radiological safety. This research, presents some statistical aspects of this optimization using frequency distributions and percentiles of individual recorded dose of industrial radiographers from the years 2002 to 2016 in Iran.

A comprehensive dose assessment of irradiated hand by iridium-192 source in industrial radiography.

Among the various incidents in industrial radiography, inadvertent handling of sources by hands is one of the most frequent incidents in which some parts of the hands may be locally exposed to high doses. An accurate assessment of extremity dose assists medical doctors in selecting appropriate treatments, preventing the injury expansion in the region. In this study, a phantom was designed to simulate a fisted hand of a radiographer when the worker holds a radioactive source in their hands.

Comparative Analysis of Neural Network Training Methods in Real-time Radiotherapy.

Background: The motions of body and tumor in some regions such as chest during radiotherapy treatments are one of the major concerns protecting normal tissues against high doses. By using real-time radiotherapy technique, it is possible to increase the accuracy of delivered dose to the tumor region by means of tracing markers on the body of patients.

Objective: This study evaluates the accuracy of some artificial intelligence methods including neural network and those of combination with genetic algorithm as well as particle swarm optimization (PSO) estimating tumor positions in real-time radiotherapy.

Type Testing of Model 7200 Automatic TLD Reader.

The type testing of measuring devices is one of the most important parts of a quality management system in a personal dosimetry services program. In this study, based upon the International Electrotechnical Commission (IEC) 62387 criteria, a reader-testing program was performed for a home-made personal thermoluminescent dosimetry (TLD) reader. The stability of the reader, the effects of light exposure, temperature and fluctuations of primary power supply on TLD read-outs as the main parameters were investigated in this program.

A root cause analysis of the high occupational doses of industrial radiographers in Iran.

The Iran Nuclear Regulatory Authority has investigated overexposure cases in industrial radiography over a period of three years. Radiographers with thermoluminescence dosimeter (TLD) records of more than 4 mSv in any 2 month routine monitoring period were asked to fill in a questionnaire explaining their points of view of the reasons for such relatively high doses. The responses showed that more than 50% of the radiographers did not agree with their recorded TLD doses, although the majority of the alternative explanations were weak.

Improvement of Accuracy in Environmental Dosimetry by TLD Cards Using Three-dimensional Calibration Method.

Introduction: The angular dependency of response for TLD cards may cause deviation from its true value on the results of environmental dosimetry, since TLDs may be exposed to radiation at different angles of incidence from the surrounding area.

Objective: A 3D setting of TLD cards has been calibrated isotropically in a standard radiation field to evaluate the improvement of the accuracy of measurement for environmental dosimetry.

Method: Three personal TLD cards were rectangularly placed in a cylindrical holder, and calibrated using 1D and 3D calibration methods.

Evaluation of Effective Sources in Uncertainty Measurements of Personal Dosimetry by a Harshaw TLD System.

Background: The accurate results of the individual doses in personal dosimety which are reported by the service providers in personal dosimetry are very important. There are national / international criteria for acceptable dosimetry system performance. Objective : In this research, the sources of uncertainties are identified, measured and calculated in a personal dosimetry system by TLD.

Comparative Measurements of Radon Concentration in Soil Using Passive and Active Methods in High Level Natural Radiation Area (HLNRA) of Ramsar.

Background: Radon and its daughters are amongst the most important sources of natural exposure in the world. Soil is one of the significant sources of radon/thoron due to both radium and thorium so that the emanated thoron from it may cause increased uncertainties in radon measurements. Recently, a diffusion chamber has been designed and optimized for passive discriminative measurements of radon/thoron concentrations in soil.

Assessment of the radiological safety of a Genoray portable dental X-ray unit.

Objectives: The portable dental radiographic systems are generally used in emergency situations (e.g. during natural disasters) for disabled/aged patients and in patient rooms.

Study of runaway electrons using dosimetry of hard x-ray radiations in Damavand tokamak.

In this work several studies have been conducted on hard x-ray emissions of Damavand tokamak based on radiation dosimetry using the Thermoluminescence method. The goal was to understand interactions of runaway electrons with plasma particles, vessel wall, and plasma facing components. Total of 354 GR-200 (LiF:Mg,Cu,P) thermoluminescence dosimeter (TLD) crystals have been placed on 118 points--three TLDs per point--to map hard x-ray radiation doses on the exterior of the vacuum vessel.

A calibration setting with uncertainty measurements for passive/active radon monitors using flow-through source type.

Based upon the steady flow method, a setting has been introduced for fast calibration of almost all types of active and passive radon detectors. In this method, a traceable radon reference flow-through sources is connected to a portable rectangular cubic transparent chamber (volume of 50 L) which is completely sealed and has 6 valves on its sides. The initializing calibration times are less than 150 min by this chamber.

Doses to the scanned individual and to the operator from an X-ray body scanner system.

The X-ray body scanner (BS) is going to find common use as a body-checking equipment at the entrance borders of countries, to find illicit drugs or forbidden items which have been hidden inside the body cavities, or attached to the body parts of the passengers. Considering the tissue weighting factors of the sensitive organs, the total effective dose due to the scanning by the system was estimated to be 3.8 µSv per scan.

Occupational dose assessment and National Dose Registry System in Iran.

This report presents status of external and internal dose assessment of workers and introducing the structure of National Dose Registry System of Iran (NDRSI). As well as types of individual dosemeters in use, techniques for internal dose assessment are presented. Results obtained from the International Atomic Energy Agency intercomparison programme on measurement of personal dose equivalent H(p) (10) and consistency of the measured doses with the delivered doses are shown.

A method for calculation of radiation quantities at all points in gamma radiation calibration fields.

Radiation quantity values at all points of a known distance range of gamma radiation calibration fields were calculated using a mathematical method. The method is based on interpolation using Chi-square test on a set of experimental data at optional points of both collimated and un-collimated calibration set-ups by means of a reference instrument. In comparison with Monte Carlo calculations, the values that were calculated by this method differ by <1% for collimated and 2% for un-collimated calibration set-ups.