فهرست مطالب

Medical Physics - Volume:15 Issue: 1, winter 2018

Iranian Journal of Medical Physics
Volume:15 Issue: 1, winter 2018

  • تاریخ انتشار: 1396/11/10
  • تعداد عناوین: 8
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  • Basim A. Almayahi *, Hakeem J. I Pages 1-5
    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 doserate 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 doserates with no adverse biological effects on people in the studied areas.
    Keywords: Background Radiation, Environment, Gamma Ray, Public Health
  • Marwan S.M. Al-Nimer *, Suad M. Al-Deen, Ibrahim T. Ibrahim Pages 6-11
    Introduction
    Low-energy helium-neon (He-Ne) laser beam lightis 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 (30µg/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.
    Keywords: Hene Laser, DNA Double Stranded, Sodium Hypochlorite, Hypochromic, Hyperchromic
  • Ehab Attalla *, Ismail Eldesoky Pages 12-18
    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
    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.
    Keywords: Multileaf Collimator, Intensity, Modulated Radiation Therapy, Dose Distribution
  • Hedieh Hassanvand, Mohammad Sadegh Hassanvand, Mehdi Birjandi, Bahram Kamarehie *, Ali Jafari Pages 19-27
    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.
    Keywords: Air Pollution, Indoor, Radon, Rn, 222
  • Soo-Foon Moey *, Zubir Shazli Pages 28-38
    Introduction
    A fine balance of image quality and radiation dose can be achieved by optimization to minimize stochastic and deterministic effects. This study aimed in ensuring that images of acceptable quality for common radiographic examinations in digital imaging were produced without causing harmful effects.
    Materials And Methods
    The study was conducted in three phases. The pre-optimization involved ninety physically abled patients aged between 20 to 60 years and weighed between 60 and 80 kilograms for four common digital radiographic examinations. Kerma X_plus, DAP meter was utilized to measure the entrance surface dose (ESD) while effective dose (ED) was estimated using CALDose_X 5.0 Monte Carlo software. The second phase, an experimental study utilized an anthropomorphic phantom (PBU-50) and Leeds test object TOR CDR for relative comparison of image quality. For the optimization phase, the imaging parameters with acceptable image quality and lowest ESD from the experimental study was related to patient’s body thickness. Image quality were evaluated by two radiologists using the modified evaluation criteria score lists.
    Results
    Significant differences were found for image quality for all examinations. However significant difference for ESD were found for PA chest and AP abdomen only. The ESD for three of the examinations were lower than all published data. Additionally, the ESD and ED obtained for all examinations were lower than that recommended by radiation regulatory bodies.
    Conclusion
    Optimization of image quality and dose was achieved by utilizing an appropriate tube potential, calibrated automatic exposure control and additional filtration of 0.2mm copper.
    Keywords: Digital Radiography, Radiation Monitoring, radiation protection, X-ray
  • Firouz Payervand, Gholamreza Raisali *, Fereshte Hajiesmaeilbaigi, Shahyar Saramad Pages 39-47
    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 within20% 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.
    Keywords: Diamond Microdosimeter, Dose, Equivalent Response, Monte Carlo, Simulation
  • Samuel Nii Adu Tagoe *, Samuel Yeboah Mensah, John Justice Fletcher, Evans Sasu Pages 48-61
    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.
    Keywords: Compensating Filter, Bolus, Regression, Modulation
  • Hassan Zarghani, Mohammadtaghi Bahreyni * Pages 62-65
    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.
    Keywords: Diagnostic X-ray, Radiography, Radiation Dosage, radiation protection