IRANIAN JOURNAL OF MEDICAL PHYSICS
Year:2018 | Volume:15 | Issue:1|Papers Count:8

Introduction: This study investigated the exposure rates of background radiations in selected locations of Najaf and Dhi Qar cities, Iraq.Materials and Methods: Exposure rates were quantified using a portable Geiger–Müller meter. Frequent readings of gamma dose rates were recorded (82 and 101 nGy h-1).Results: The lowest absorbed dose rate was found to be 43.5±17.4 nGyh-1 in Najaf (outdoor environments), and the highest was 174±8.7 nGy h-1 in Dhi Qar city (outdoor environments). Overall, the absorbed dose rates of background radiation fell within the worldwide range reported in other regions.Conclusion: The selected locations in Najaf and Dhi Qar cities showed normal absorbed dose rates with no adverse biological effects on people in the studied areas.

Introduction: Low-energy helium-neon (He-Ne) laser beam light is used in combination with sodium hypochlorite (Na2HOCl3) for clinical purposes. Regarding this, the present study aimed to investigate the effect of He-Ne laser (632.8 nm) and sodium hypochlorite on the calf thymus double-stranded deoxyribonucleic acid (ctdsDNA) molecule.Materials and Methods: For the purpose of the study, ctdsDNA solutions (30mg/ml) were exposed to He-Ne laser (632.8 nm) light in the absence and presence of different concentrations of sodium hypochlorite for up to 60 sec. The levels of nucleic acids released as uncontaminated and contaminated proteins were considered as the markers of DNA damage in terms of hypochromasia (i.e., DNA strand breakage) and hyperchromasia (i.e., of DNA strands separation).Results: The mean concentration of nucleic acids insignificantly (P>0.05) decreased after exposure to laser light irradiation (hypochromic effect). Furthermore, laser irradiation insignificantly and inconsistency protected the ctdsDNA molecules from the effect of sodium hypochlorite. Sodium hypochlorite at concentrations of 1 and 3 mmol reduced the levels of the nucleic acids released from contaminated protein by 29.2% and 78.3% of the pre-incubated levels (hyporchromasia effect). The He-Ne laser (632.8 nm) irradiation induced hypochromic effect on the uncontaminated and contaminated proteins, while sodium hypochlorite induced a remarkable hyperchromic effect at higher concentrations.Conclusion: As the finding indicated, a short time He-Ne laser light (632.8 nm) irradiation exerted minor significant effect on the ctdsDNA molecule. This laser light did not interact with sodium hypochlorite as a synergistic combination against the ctdsDNA molecule.

Introduction: Geometric changes in the multileaf collimator (MLC) led to dosimetric considerations in intensity-modulated radiation therapy (IMRT) due to the number and size of the pixels in the intensity map, which are determined by the MLC leaf width. In this study, we evaluated the dosimetric effects of different MLC widths on physical dose distributions for IMRT plans.Materials and Methods: Forty-two IMRT plans based on different MLC devices were generated and analyzed to study the effect of MLC width on plan quality.Results: Improvements in IMRT plan quality using 0.4 cm leaf width in comparison with 1 cm leaf width were evaluated. The 0.4 cm leaf-based plans resulted in significantly higher Dmean, D98%, D95%, D5%, and V95 (58.86 Gy, 95.11%, 96.57%, 104%, and 97.92%, respectively) compared to the 1 cm leaf plans (58.66 Gy, 92.56%, 94.56%, 104.14%, and 95.72%, respectively). Conformation number (CN) for planning target volume in 0.4 cm leaf plans was significantly higher than the 1 cm leaf plans (0.74 vs.0.67; P<0.05). In addition, the 0.4 cm leaf plans significantly improved dose homogeneity compared to the 1 cm leaf plans (1.08 vs.1.10; P<0.05). We found that 0.4 cm leaf width significantly decreased the integral dose to normal tissue compared to the 1 cm leaf width (from 56.09 to 49.46 Gy.Kg P<0.05).conclusion: No significant clinical differences were observed between the two plans for a serially functioning tissue, while the differences in mean doses were statistically significant for parallel functioning normal tissues.

Introduction: Exposure to indoor radon increases the risk of lung cancer. This study examined the level of indoor radon in dwellings of Khorramabad city, by using passive alpha-track detector (CR-39) during winter of 2016.Materials and Methods: In the present study, we detected the concentration of indoor radon in 56 dwellings. A passive sampling instrument (alpha-track detector with CR-39 polycarbonate films) was utilized to measure indoor radon gas concentration. The distribution map of indoor radon concentration was prepared using Arc GIS software.Results: Radon concentration in the dwellings varied from 1.08 to 196.78 Bq/m3, with a mean value of 43.43±40.37 Bq/m3. The average annual effective dose received by the residents of the studied area was estimated to be 1.09 mSv. Our results showed a significant difference between the average radon concentrations in houses and apartments, with a higher level in houses.Conclusion: Indoor radon concentration in 10.1% of the dwellings was determined to be higher than the limit (100 Bq/m3) recommended by the World Health Organization.

Introduction: Optimization facilitates image quality and radiation dose by minimizing stochastic and deterministic effects. This study was to obtain images of acceptable quality with no harmful effects for common radiographic examinations in digital imaging.Materials and Methods: This study was conducted in three phases. The pre-optimization phase involved 90 physically able patients weighing 60-80 kg and aged 20-60 years. The estimation of dose and image quality was performed on four common digital radiographic examinations. The entrance surface dose (ESD) and effective dose (ED) were measured using a DAP meter (Kerma X_plus) and CALDose_X 5.0 Monte Carlo software, respectively. The second phase, an experimental study utilized an anthropomorphic phantom (PBU-50) and TOR CDR Leeds test object for comparison of image quality. In the optimization phase, the imaging parameters with acceptable image quality and lowest ESD from the experimental study were adjusted for patient’s body thickness. Image quality was evaluated by two radiologists using the modified evaluation criteria score lists.Results: A significant difference was observed between the pre- and post-optimization phases for all examinations for image quality. However, ESD was significantly different between the two phases for PA chest and AP abdomen. The ESDs for three of the examinations were lower than those reported in all published studies. The ESD and ED obtained for all examinations were lower than recommended by radiation regulatory bodies.Conclusion: The optimization of image quality and dose was achieved by utilizing an appropriate tube potential, calibrated automatic exposure control, and additional filtration of 0.2 mm copper.

Introduction: Microdosimeters are helpful for dose equivalent measurement in unknown radiation fields. The favorable physical and mechanical properties of the detector-grade chemical vapor deposition diamond materials have made the diamond microdosimeters suitable candidate for radioprotection applications in space. The purpose of this work is the investigation of the dose equivalent response of a typical diamond microdosimeter with laser-induced graphitized electrodes for use in space radiation fields.Materials and Methods: The Geant4 Monte Carlo simulation toolkit was applied to simulate the particle transport within the microdosimeter, and to determine the mean chord length and the dose equivalent response of the microdosimeter, based on the lineal energy dependent quality factor.results: The linear stopping power of the protons and alpha particles with energies higher than 5 MeV and 10 MeV respectively can be estimated within 20% of deviation using the microdosimeter response. The fluence to dose equivalent conversion coefficients calculated affirms that there is an adequate agreement between the calculated coefficients and other research group results.Conclusion: The reasonable agreement between the dose equivalents calculated in this study and the results reported by other researchers confirmed that this type of microdosimeter could be a promising candidate suitable for the measurement of the dose equivalent in space radiation fields.

Introduction: The present study aimed to generate intensity-modulated beams with Aluminium compensating filters for a conventional telecobalt machine based on the outputs of a treatment planning system (TPS) performing forward planning and cannot simulate directly the compensating filter.Materials and Methods: In order to achieve the beam intensity modulation during treatment planning with the TPS, we used a bolus placed on the surface of a tissue-equivalent phantom. The treatment plans replicated on the telecobalt machine with the bolus were represented with compensating filters placed at a certain distance from the phantom surface. An equation was proposed for the conversion of the bolus thickness to the compensating filter thickness such that any point within the phantom would receive the planned dose. Correction factors were introduced into the proposed equation to account for the influences of field size, treatment depth, and applied bolus thickness. The proposed equation was obtained based on the analyses of empirical data measured in a full scatter water phantom with and without the compensating filter.Results: According to the results, the dosimetric verification of the proposed approach outputs in a solid water phantom with calibrated Gafchromic EBT2 films were comparable to that of the TPS with deviation of ±4.73% (mean: 2.98±1.05%).Conclusion: As the findings of the present study indicated, the discrepancy between the measured doses and TPS-estimated doses was within the tolerance of ±5%, which is recommended for dose delivery in external beam radiotherapy. Therefore, the proposed approach is recommended for clinical application.

Introduction: Diagnostic reference level (DRL) is a useful tool for the promotion of optimization. The national DRLs (NDRLs) are useful, brief, and robust guidelines for optimizing radiation protection in a country. The aim of this study was to extract the local DRLs (LDRLs) for some common radiologic examination in Sabzevar county.Materials and Methods: There are eight radiology departments in Sabzevar County, Iran. The entrance skin dose (ESD) distributions were determined by use of thermoluminescence dosimeter (TLD) chips for 10 standard projections (i.e., anterioposterior [AP] abdomen, AP and posteroanterior [PA] chest, AP and lateral [LAT] lumbar spine, AP pelvis, cervical AP, cervical LAT, as well as AP and LAT skull). The third quartiles of the measured ESDs were compared with the previously published data.Results: In the present study, the third quartile of the measured ESDs for the patients undergoing specific examination were selected as LDRLs. The calculated LDRLs for the chest PA, chest AP, lumbar spine PA, lumbar spine LAT, pelvis AP, abdomen AP, cervical AP, cervical LAT, skull PA, and skull LAT were 0.54, 0.64, 1.99, 3.83, 1.47, 2.15, 0.54, 0.78, 1.22, and 1.01 mGy, respectively.Conclusion: Our results were compared with the DRLs reported in Iran, UK, and Japan as well as those reported by the National Radiological Protection Board (NPRB) for the UK. The ESDs obtained in this study for the chest PA, cervical AP, cervical LAT, AP and LAT skull, abdomen AP, pelvis AP, lumbar PA, and lumbar LAT examinations did not exceed the DRL values reported by NPRB.