International Journal of Radiation Research
Year:2020 | Volume:18 | Issue:2|Papers Count:22

Background: In this proposed work, the products of 238U radioactive decomposition: 226Ra, which has a comparatively great decomposition period and 228Ra intermediate product of 232Th were examined, which were more prevalent in water samples of the territories investigated. Natural radionuclides are usually observed more in artesian well waters than in river and canal waters, and less in comparison with groundwater. Materials and Methods: For studying the concentration of radionuclides in drinking and agricultural water, samples were collected from Kura River, Yukhari Garabakh and Yukhari Shirvan channels and from artesian wells in different regions. For measurement of radioactivity, gamma spectrometer with high-sensitivity Ge-detector was used, controlled by the software Genie 2000 (manufactured by CANBERRA firm). Results: The obtained results for well waters showed high activity concentrations; the total effective doses for all radionuclides were 2. 54, 4. 27, and 0. 66 mSv for infants, children, and adults, respectively. Conclusion: From these results, it can be concluded that the investigated water is not acceptable for life-long human consumption.

Background and Aim: The incidence of internal lymph node (IMN) involvement was 4-65% in breast cancer patients. Despite studies indicating the positive effects of IMNRT on the oncological results, most of the clinicians avoided IMNRT because of the toxicity related to the increased dose of organs at risk (OAR). We aimed to compare the dosimetric results of RT plans with and without IMN containing planning target volumes (PTVs) using helical tomotherapy (HT) in obese patients. Materials and Methods: The PMRT data of 23 obese patients were evaluated retrospectively / dosimetrically. Two PTVs with and without IMN were defined and two separate plans were made with HT. Dose received by IMN and OAR were compared. Results: The untargeted IMN V40 were calculated between 0% to 99%. When the plans are evaluated in terms of critical organs, the inclusion of the IMN into the target volume, the most significant adverse effect was observed in heart doses in the left chest wall (CW) irradiation. The significant increases in cardiac V5 (% 62. 6 vs %48. 6 p=0. 007), V10 (%38. 2 vs %23. 2 p=0. 011), V20 (%14. 15 vs %9. 06 p=0. 045) and maximum heart dose (48. 04 vs 43. 2 p=0. 043) were observed in the left-side CW irradiations that involving the IMN. In CW irradiation on the right side with IMN, only a significant increase in mean heart dose (5. 44 vs 4. 52 p=0. 036) was observed. Lung V5 doses were increased by inclusion with IMN in both sides. There was no difference in the contralateral breast doses in both plans for both sides. Conclusions: If the IMN is not targeted, some of the patients are getting appropriate doses in obese patients.

Background: In gamma-ray spectrometry for the radioactivity analysis of bulk samples, self-attenuation correction is necessary when the attenuation rates in test sample differ from the one in the efficiency calibration source. Thus, the mass attenuation coefficient of test samples is an important factor in gamma-ray spectrometry. This study estimates the mass attenuation coefficients for seven kinds of environmental samples. Materials and Methods: An uncollimated transmission system with a high purity germanium detector system was used to measure the gamma-ray transmission rates with and without test samples. The system was calibrated using C (activated charcoal), H2O, MnO2, NaCl, Na2CO3, and (NH4)2SO4 as reference materials. Sea sediment, surface soil, fish, seaweed, Chinese cabbage, milk, and pine needles were selected, and ten identical samples for each sample type were tested using the system. Results: The calibration of the uncollimated transmission system was validated with good agreement within 4% between linear attenuation coefficients by experiment and calculation for K2CrO4 and SiO2. The standard deviation of the mass attenuation coefficients for each kind of sample was estimated as less than 5% above around 100 keV. Conclusion: Mass attenuation coefficient does not significantly depend on the sample type for gamma-ray energy higher than around 100 keV, but mass attenuation coefficient for the lower gamma-ray energy should be considered even with similar kinds of sample. The mass attenuation coefficients tabulated in this paper can be used as a reference or comparable value in gamma-ray spectrometry for environmental samples.

Purpose: This study was conducted to evaluate single collimator (SC) and double collimator (DC) plans with respect to dosimetric analysis, calculated dose delivery to OAR and treatment time in carcinoma prostate patients treated with cyberknife. Materials and Methods: A retrospective study was conducted among twenty low and intermediate risk carcinoma prostate previously treated with Cyberknife. PTV was created and OARs were delineated. The prescribed dose was set as 37. 5 Gy in 5 fractions and a base plan (BP), followed by three reduction plans (time, beam and node) were generated for both single and double collimators with sequential optimization module. The SC and DC plans were compared for the above-said variables. The mean differences were compared using paired t-test. A p-value of <0. 05 was taken as statistically significant. Results: The median age of the patients was 63 years. DC plans had tighter isodose lines. The means of minimum doses did not vary significantly across the plans but the mean and maximum doses, PTV D2 and V95 means were significantly higher in single collimator plan. The mean CI and HI values were better in DC plans. The doses to OAR were comparable in both single and double collimator plans in terms of maximum doses. The mean doses received by OAR’ s were significantly lesser in DC plans. SC plans resulted in lesser beams, nodes, MU and treatment time. Conclusion: Double collimator plans were better in producing good dosimetric results and reduced OAR doses with lesser estimated treatment efficiency.

Background: Small field dosimetric challenges lead to a deviation from the reference dosimetry. The aim of this study is to investigate the changes of polarization (kpol) and ion recombination (ks) correction factors and determination of leakage dose in small fields. Materials and Methods: All values were measured on a RW3 slab phantom, at 100 cm Source-to-Surface Distance, 10 cm depth and 6, 10 and 18 MV photon beams for square fields (0. 5 to 10 cm). Three ionization chambers (PTW Pinpoint 31014 and 31015, Semiflex 31010) were hired. After the electrometer readout, the correction factors were computed according to the protocol No. 398 of International Atomic Energy Agency's Technical Report (IAEA TRS-398). Results: The kpol (min) and the kpol (max) value occurred in 0. 5×0. 5 cm2 and 10×10 cm2 field size, respectively. Dosimeters with a larger sensitive volume showed greater kpol values. In all three dosimeters, an increasing trend detected in normalized dosimeter reading after working voltage. The level of leakage in all of the values and radiation conditions was at the level of a few Nano colons. Conclusion: The values of kpol and ks in the small fields were different from the reference field. The saturation voltage of the small field dosimeters was greater than the dosimeter working voltage. The leakage values of the dosimeter-electrometer combination in the present study were negligible for all radiation conditions. The correction factors should be considered due to the differences between small fields and reference dosimetric conditions.

Background: Radon is one of the most important radionuclides, formed from the decay of the element radium and more soluble in water. As drinking water is a vital source of life, control of its quality is critical. Drinking water containing high radon levels presents a serious risk to human health. Thus awareness of radon levels in drinking water is extremely significant to protect against radiation exposure. We measured 222Rn concentrations in different types of drinking water from Qena city, Egypt. Materials and Methods: 111 water samples were collected from various sources in Qena city (77 samples of household tap water, 14 samples of bottled water and 20 samples from municipal public water supply locations). The 222Rn concentrations were determined using an AlphaGUARD radon gas analyzer. We calculated annual effective dose due to ingestion and inhalation of 222Rn present in these waters. Results: 222Rn concentration ranges were as follow: 22. 0± 0. 7 to 118± 3 mBq l-1, from tap water 14± 3 to 237± 5 mBq l-1 from bottled water and 6. 0± 0. 5 to 30. 0± 0. 9 mBq l-1 from municipal public supplies. The annual effective dose due to inhalation and ingestion of 222Rn in all types of drinking water measures less than the recommended reference level of 100 μ Sv y-1. Conclusion: Based on the obtained results, 222Rn concentrations in the studied water samples were less than the permitted concentrations of USEPA and WHO guidelines.

Background: Recently, several diagnostic radiopharmaceuticals including bleomycin (BLM) derivatives have been developed. Due to the suitable physical and chemical characteristics of 68Ga as a radionuclide for PET imaging, in this study, optimized production, quality control and preclinical evaluation of 68Ga-BLM as a new PET imaging agent is reported for the first time. Materials and Methods: Labeling of BLM with 68Ga was performed using 68Ge/68Ga generator. Experiments were carried out by changing BLM concentration, temperature and pH of the reaction to determine the optimum parameters while the radiochemical purity was checked by radio thin layer chromatography at different times post labeling. Stability of the radiolabeled complex was studied at room temperature and in human serum at 37 ° C. Biodistribution of the complex in BALB/c mice was assessed after intravenous injection and by counting the activity of each organ. Also, images were acquired up to 120 min by dual-head SPECT system. Results: The purity of this complex >96% (ITLC). At the optimized conditions for preparation of 68Ga-BLM (pH= 3. 5-4, temperature = 90 º C, reaction time = 15 minutes and ligand concentration of 1 mg/ml), the special activity of the labeled BLM reached to around 17. 5 GBq/mmol. Biodistribution study showed significant accumulation of radioactivity in lung and bladder that was different pharmacokinetic compared to free 68Ga cation. Conclusion: Results show that 68Ga-BLM can be prepared in high radiochemical purity and high special activity only in 15 minutes and totally can be considered as a high potential agent for PET imaging.

Background: The aim & objective of this study is to evaluate the health hazards of the general public from the existence of the radioactive nuclides in soil of North Waziristan and to establish a reference line for future work on radioactivity concentration in this locality. Methods and Materials: A highly background radiation shielded HPGe system is used to measure radioactivity in the collected samples of the geographical study area. Results: The radioactivity concentration is found to be in the range 42. 6– 106. 3 Bq/kg for Ra-226, 4. 0– 93. 8 Bq/kg for Th-232, 49. 9– 645. 5 Bq/kg for K-40, and 2. 6– 8. 33 Bq/kg for Cs-137. The external and internal hazards indices (Hext & Hint), absorbed γ-dose rate (ADR) and average effective dose (AED) are estimated from the computed activities and determined the average Hext ~ 0. 75 and Hint ~ 0. 94. The mean absorbed dose rate was found to be 101 nGy/h. The Radium equivalent activity of Datta Khel (422. 081 Bq/kg), Khaisur forest (407. 938 Bq/kg), Jani Khel (379. 213) specific regions and the corresponding outdoor annual effective dose rate was found to be 0. 15 mSv/yr, which is higher than the world’ s mean value of 0. 07 mSv/yr. Conclusion: A strong possitive correlation amongst the radioactive nuclides and, corresponding radiological variables at P ≤ 0. 01confirmed that Ra-226 and Th-232 were the significant contributors to γ-radiation emission. Radioactivity concentrations and corresponding radiometric parameters were found to be higher in the specific areas of North Waziristan compared to the world’ s mean values poses possible radiological risks for the residents of those areas.

effect in different malignancies. In this research, we treated Glioblastoma multiform (GBM) patients with hyperthermia (HT) along with the chemoradiation, in order to evaluate HT efficacy in terms of tumor volume changes, survival time, and probability. Materials and Methods: Thirty-eight GBM patients were distributed into two groups identified as chemoradiation (CRT), and also CRT plus HT (CRHT). The Karnofsky Performance Status Scale (KPS) was done before, immediately and three months after treatments. Capacitive hyperthermia device was used at frequency of 13. 56 MHz (Celsius 42+ GmbH, Germany) for HT one hour before the radiotherapy for 10-12 sessions. Patients in both groups underwent MR imaging (1. 5 Tesla) before, 3 and 6 months after the treatments. Thermal enhancement factors (TEF) were attained in terms of clinical target volume changes, TEF(CTV), and survival probability (SP) or TEF(SP). Results: Age ranges were from 27-73 years (Mean=50) and 27-65 years (Mean=50) for CRT and CRHT groups, respectively. For 53% and 47% of cases biopsy and partial resection were accomplished in both groups, respectively. Means and standard deviations of tumor volumes were 135. 42± 92. 5 and 58. 4± 104. 1cm3 before treatment in CRT and CRHT groups, respectively, with no significant difference (P= 0. 2). TEF(CTV) value was attained to be as 1. 54 and 1. 70 for three and six months after treatments, respectively, TEF(SP) was also equal to the 1. 90. Conclusion: HT enhanced the chemoradiation effects throughout the patient survival probability and KPS. TEF may reflect the hyperthermia efficacy for a given radiation dose.

Background: Among all of the radiations, X-ray has been always the center of attention due to the increasing availability of the X-ray tubes in industry, research institutes and medical centers. In this study, X-ray shielding properties of bulk and nanostructured thin lead films were investigated by means of Monte-Carlo computational and experimental methods, respectively. Materials and Methods: The lead samples were fabricated by the Physical Vapor Deposition technique (PVD) with different thickness of 10, 100 and 1000 nm. To investigate the radiation shielding properties of the nanostructured thin films, all of the prepared samples were subjected to the X-ray ranging from 8 to 14 keV. In order to consider the shielding properties of the bulk-structured thin films, the Monte-Carlo MCNPX code was employed. Results: The results indicated that, for low X-ray energies, the nanostructured thin lead films attenuate more than bulk-structured samples; however, the difference disappears as film thickness increases to 1000 nm or X-ray energy reaches 14 keV. Conclusion: Results imply that the nanostructured thin lead films attenuate more photons than the bulkstructured thin lead films with the same thicknesses.

Background: X-irradiations induce damages to the hematopoietic system by reducing the production of blood cells in bone marrow. In this study, the radioprotective effect of arbutin was investigated in megavoltage x-irradiated mice by measuring changes in hematological parameters and lymphocyte cells with micronucleus assay. Material and Methods: Sixty NMRI mice were irradiated with 6 MV photon beam (2 and 4 Gy in one fraction). Various concentrations of arbutin (50, 100, and 200 mg/kg) were injected intraperitoneal, 2 hours before whole body X-irradiation. Samples of peripheral blood cells were collected from the left ventricle. The frequency of micronuclei in 1000 cells were measured for each sample and level of peripheral blood cells were analyzed. The data were statistically evaluated using one-way ANOVA, and Tukey HSD test. Results: X-radiations significantly decreased the hematological parameters such as white blood cells (WBC), lymphocyte (LYM), red blood cells (RBC) counts, and hemoglobin (HGB) levels compared to the control group (P < 0. 001). The frequency of micronuclei in “ 2 and 4 Gy X-irradiation + distilled water” groups was significantly higher than “ 2 and 4 Gy irradiation + 50 mg/kg arbutin” , “ 2 and 4 Gy irradiation + 100 mg/ kg arbutin” , and “ 2 and 4 Gy irradiation + 200 mg/kg arbutin” groups, followed by the above-mentioned blood cell parameters were dropped remarkably. Conclusion: The present investigation showed that arbutin is a strong radioprotector. There were not any significant differences between the various concentrations of arbutin, however, the concentration of 50 mg/kg showed higher radioprotective effect.

Background: To evaluate the radiosensitizing effect of co-targeting of poly (ADP-ribose) polymerase-1 (PARP1) (AZD2461) and phosphoinositide-3-kinase (PI3K) (LY294002) in breast cancer 1, early onset gene (BRCA1)-mutated triple negative breast cancer (TNBC) treated in vitro. Materials and Methods: We established HCC1937-PARP1 cells by transfection. Cell proliferation, cell viability, cell cycle, and cell apoptosis were measured and analyzed. Western blotting and quantitative real-time polymerase chain reaction assays were performed. Results: The cell viability of HCC1937 and HCC1937-PARP1 cells was significantly decreased under 5 Gy of irradiation. Cell apoptosis was remarkably increased by irradiation, whereas overexpression of PARP1 resulted in substantial resistance to the radiation-induced changes. Combined inhibition of PARP1 and PI3K enhanced radiation-induced apoptosis and significantly inhibited cell proliferation compared with single-agent treatment. The PI3K inhibitor induced changes in the cell cycle distribution, but the PARP1 inhibitor did not. The expression levels of LKB1, PHLPP and INPP4B increased after combined inhibition of PARP1 or PI3K compared with irradiation alone. Moreover, combined inhibition of PARP1 and PI3K resulted in increased expression of INPP4B when compared with that induced by single-agent treatment. Conclusion: Combined inhibition of PARP1 and PI3K might be an effective therapeutic strategy to enhance radiosensitivity in BRCA1-mutated TNBC.

Background: Dose modulation is a key factor in practical proton therapy. This study investigates the dose modulation methodology of irregular radiation field (IRF)-based proton therapy using forward radiation treatment planning and conformal dose layer stacking (CDLS) methods. Materials and Methods: The geometric configuration of a virtual multi-leaf system was constructed to generate IRFs during Monte Carlo simulations. Two patient geometries— lymphatic metastasis and brain tumors— were configured to investigate the dosimetric feasibility and applications of IRF-based proton therapy in ideal patient anatomies. The investigated tumors were divided into slices perpendicular to proton beam axis. Segments were designed to be conformal to the profiles of these tumor slices. Conformal dose layers were produced by modulating the proton intensities and energies of the predesigned segments. Then, these dose layers were stacked throughout the tumors to obtain sufficient and conformal tumor doses. Results: From the proposed IRF-based proton therapy, tumors with 4-7 cm extents along the depth direction could be treated with fewer than 10 segments. The lymphatic metastasis and brain tumors were sufficiently covered by 95% dose lines, while appropriate distal and proximal dose conformities were achieved. The maximum tumor doses did not exceed 110%. Conclusions: Theoretically, the proposed IRF-based proton therapy using forward planning and CDLS methods is feasible from the viewpoint of dosimetry. This study can serve as a foundation for future investigations of potential proton therapy methods based on fast conformal dose layer stacking using radiation fields with irregular shapes.

Background: Several investigations reported the dosimetric properties of flattening filter free photon beams to enhance the entrance dose in the surface and build up region. This paper was aimed to investigate the effect of the flattening filter free to enhance the dose at the surface and buildup region. Materials and Methods: A 12 MV photon beam of a linear accelerator was modeled and developed in both flattening filter and flattening filter free modes using the Monte Carlo BEAMnrc code. For both modes, the beam dosimetric features, including central axis absorbed doses and photon energy spectra were investigated. Results: A remarkable increase in the dose rate on the surface and build up region were attained with the flattening filter free mode. At the depth of 0 mm on 2×2 cm2, 4×4 cm2, 5 × 5 cm2, and 10×10 cm2 field sizes, the surface doses between flattening filter mode and flattening filter free mode were augmented from 27. 33% to 33. 78%, from 28. 89% to 35. 75%, from 29. 44% to 36. 39%, and finally from 35. 10% to 47. 46%, respectively. At the depth of 25 mm for field size from 2×2 cm2 to 10×10 cm2, the buildup doses for flattening filter mode and flattening filter free mode were augmented from 124. 89% to 136. 72% and from 132. 21% to 142. 67%, respectively. Conclusion: A significant increase in the entrance and buildup dose rate was observed when using an unflattened photon beam, which can be a benefit for the treatment of some skin cancers.

Background: The current study aimed to compare the tumor control probability (TCP) and normal tissue complication probability (NTCP) of threedimensional conformal radiation therapy (3D-CRT) and intensity-modulated radiation therapy (IMRT) for left-sided breast cancer using radiobiological models. Methods: This study was conducted on 30 patients with left-sided breast cancer, who were planned for 3D-CRT and 6-9 fields IMRT treatments using the PROWESS treatment planning system. The planning target volume (PTV) dose of 50 Gy was administered for the 3D-CRT and IMRT plans, respectively. The Niemierko’ s equivalent uniform dose (EUD) model was utilized for the estimation of tumor control probability (TCP) and normal tissue complication probability (NTCP). Results: According to the results, the mean TCP values for 3D-CRT, 6-fields IMRT, and 9-fields IMRT plans were 99. 07 ± 0. 07, 99. 24 ± 0. 05 and 99. 28 ± 0. 04, respectively, showing no statistically significant difference. The NTCPs of the lung and heart were considerably lower in the IMRT plans, compared to those in the 3D-CRT plans. Conclusions: From the radiobiological point of view, our results indicated that 3D-CRT produces a lower NTCP for ipsilateral lung. In contrast, for TCP calculations, there was a higher gain with IMRT plans compared to 3D-CRT plans.

Background: The question of whether low levels of non-ionizing radiations such as the radiofrequency electromagnetic fields (RF-EMF) can induce the same positive immune responses remains unanswered. This study aimed to investigate the effects of non-ionizing RF-EMF on some parameters of the immune system in an animal model following infection with Salmonella Typhimurium and Klebsiella pneumoniae. Materials and Methods: Male BALB/c mice were exposed to RF-EMFs generated by a common GSM mobile phone for 3 days. Animals were infected with K. pneumonia or S. Typhimurium on the 4th day. On the7th day after injection, blood samples were collected by cardiac puncture. The specific antibodies against bacteria were determined by agglutination method and serum levels of the cytokines were measured using the ELISA method. Moreover, the leukocytes count was measured using a cell counter. Results: The levels of specific antibodies against bacteria were higher in non-irradiated mice compared to irradiated mice. There were no significant differences between the irradiated and non-irradiated mice regarding the total blood leukocyte count. The mean serum levels of IFN-γ and IL-17 after infection with K. pneumoniae were significantly higher in the irradiated mice (p<0. 001). Conclusions: Low levels of RF-EMF can stimulate the immune responses in the mice pre-exposed to RF-EMF. This study provides further evidence supporting that exposure to certain levels of RF-EMF can stimulate the immune system. These adaptive responses may be applied to cope with the increased susceptibility of the astronauts to infections during a deep space mission.

Background: We aimed to investigate the chest high-resolution computed tomography (HRCT) imaging manifestations of patients with coronavirus disease 2019 (COVID-19) pneumonia. Materials and Methods: Chest HRCT images of 12 patients who were diagnosed as COVID-19 pneumonia in our institute from January 28, 2020 to February 16, 2020 were retrospectively reviewed. Results: The most typical HRCT findings were bilateral pulmonary parenchymal ground-glass opacities, with or without consolidation in the lung periphery, and sometimes also showed a rounded morphology. Three (25%) patients had typical crazy paving signs, 3 (25%) patients showed air bronchogram, 2 (16. 67%) patients with bronchial wall thickening signs, and 5 (41. 67%) patients had vascular perforator signs. Only one (8. 33%) patient had unilateral involvement in the left upper lobe. Lung cavitation, pleural effusions and intrathoracic lymph node enlargement were not found in all patients. The severity of the lesions in the right lung, and in the lower lobe were worsen than those in the left lung and upper lobe, respectively. Lesions in the lateroposterior zone of the lung were more common than those in the apical and central areas. Notably, 9 (75%) patients with chest HRCT findings related to COVID-19 pneumonia had negative results of concurrent nucleic acid tests. Conclusion: Chest HRCT can provide an important basis for early clinical diagnosis of COVID-19 pneumonia, and help subsequent intervention for the patients to stop further transmission, especially consider that the mild clinical symptoms and the initial negative results of nucleic acid tests of these patients are common.

Background: The increasing health effects of nuclear radiation occasioned by enhanced human activities in the environment necessitated the need for constant evaluation and assessment of radiological impact on the general populace within a confined developmental area. Hence, Ten (10) drilled well water samples were collected from various cities distributed across Ondo and Ekiti states and analyzed for gamma-emitting radiations. Materials and Methods: The collected water samples were analyzed using n-type co-axial HPGe detector (Canberra Inc, USA), to determine the activity concentrations of the gamma emitting radiations, which was used with dose conversion factors to calculate the age dependent total annual effective dose equivalents to six different age groups and the committed effective dose for the age group >17y. Results: Activity concentrations ranged from 2. 25± 0. 39 to 35. 61± 6. 22 Bq l-1232Th, 7. 08± 1. 71 to 56. 68± 12. 50 Bq l-1226Ra, 45. 42± 2. 98 to 467. 61± 31. 69 Bq l-140K and 1. 66± 0. 46 to 25. 55± 5. 76 Bq l-1232Th, 4. 90± 1. 08 to 54. 18± 13. 34 Bq l-1226Ra, 41. 50± 2. 89 to 558. 82± 31. 69 Bq l-140K, respectively for Ondo and Ekiti States. Furthermore, the mean total annual effective dose equivalent for the age groups was found to be within the range of (2. 81 ± 0. 46 – 26. 91 ± 5. 11) mSv/y and (4. 71 ± 0. 92 – 23. 58 ± 5. 12) mSv/y respectively for Ondo and Ekiti states. Conclusion: This is above the 1. 0 mSv y-1 and 0. 1mSv y-1 respectively set by ICRP and WHO. Hence, the drilled wells are recommended for water screening to remove radionuclides.

Background: Radon is a normally occurring radioactive material, which is designated as a class 1 human carcinogen. Therefore, it is important to control radon exposure in dwellings and workplaces. Methods: The radon guidelines of 32 countries across Europe, North America, and Asia were examined to determine rational radon exposure standards for minimizing radon risk in dwellings, offices, and workplaces. The exposure standards were classified as standards for people in dwellings and offices, where radon exposure can occur through construction materials, and standards for workers exposed to radon at industrial sites, where they directly handle products containing radioactive matter such as raw materials and by-products from processing. Results: The examination results showed that in South Korea, the advisory reference level (ARL) for dwellings is set to 148 Bq/m3. Moreover, ARLs are set for subway stations, libraries, medical institutions, and indoor parking lots, but there are no radon exposure standards to protect workers in manufacturing sites, officers, and other workplaces. In other countries, the ARL or the mandatory reference level (MRL) are usually regulated between 148– 400 Bq/m3 for dwellings and public-use facilities, and between 200– 1, 000 Bq/m3 for workplaces. Conclusion: It is recommended to use 148 Bq/m3, which is the standard set by the U. S. Environmental Protection Agency, for dwellings and workplaces. For workplaces, it is recommended to set the exposure standard between 400 Bq/m3, which is the level adopted in most European Union member countries, and 1, 000 Bq/m3, which is the reference level recommended by the International Commission on Radiological Protection.

Background: Patients with head-and-neck cancers receiving radiotherapy show significant anatomical and dosimetric changes, especially during the latter part of treatment. The aim of this study is to evaluate the dosimetric effects of an adaptive Volumetric Modulated Arc Therapy (VMAT) treatment protocol for patients with locally advanced nasopharyngeal cancer (NPC). Material and methods: Ten patients treated with VMAT have benefited from a second computed tomography scan (CT2) after 15 fractions in order to apply a new adapted plan. A hybrid plan has been generated applying the original treatment plan configuration beam to the second CT scan. The dose– volume histograms (DVHs) of hybrid and adapted plans have been compared. Results: At the end of the 3rd week of treatment, CT2 shows a considerable shrinkage of GTV N70 volume (45. 2%) and a diminution of the left and right parotid glands volume (21. 1%, 20. 6% respectively). Compared to the initial plans, hybrid plans reveal that the dose delivered to target volume GTV N70 decreased by 15. 2%, and the V30 of the left and right parotid glands increased by 47. 3% and 25. 6% respectively. However, there is no significant difference for the D2 of the brainstem and spinal cord. Conclusion: Our adaptive VMAT protocol improves dosimetric results in terms of GTV N70 coverage and nontoxic doses to parotid glands.

Background: Endoscopic retrograde cholangiopancreatography (ERCP) is now widely used in the diagnosis and treatment of gastrointestinal tract disorders. A large number of X-ray fluoroscopy and digital radiographs make ERCP as an interventional radiological procedure. In this study, patients' and examiner's entrance skin doses (ESDs) were measured during diagnosis and treatment procedures and patients' effective dose (ED) were calculated. Materials and Methods: Thermoluminescent dosimeters (TLDs) and dose area product meter (DAP) were used to measure ESDs of 30 patients and examiner and calculate patients' ED. Besides, to assess the effectiveness of an extra lead shield in decreasing examiner's ESDs, a lead cover was wrapped around the Xray tube. The data were analyzed with IBM SPSS Statistics version 16 software. Results: The mean DAP and fluoroscopy time (FT) of the diagnostic procedure were 4. 09 Gy. cm2 and 32. 4 s while those of the therapeutic procedure were 7. 60 Gy. cm2 and 76. 2 s. The strong linear correlation between DAP and FT was observed for the therapeutic procedures but the diagnostic ones. The patients' mean EDs of diagnostic procedure (1. 21± 0. 52 mSv) and therapeutic one (2. 25± 1. 72 mSv) were calculated. Moreover, the shielding cover around the X-ray tube decreased ESDs of the organs of interest except gonads. Conclusions: The results reveal that therapeutic ERCP procedure imposes a greater radiation dose compared to diagnostic ERCP one. However, the doses of the patient and the examiner depend highly on examiner's experience, technical skills and knowledge in radiation protection. The results suggest that attempts to reduce radiation doses should be made.

Background: The present study aimed to determine half-value layers (HVL) of different materials with neutron, photon, and simultaneous neutron and photon emissions by a 252Cf source. MCNPX code was used for the simulation of the applicator tube (AT) 252Cf source and the attenuation materials. Materials and methods: The 252Cf source, a source collimator, a detector, a detector collimator, and HVL material were defined in the present study. HVL was determined for lead, concrete, water, polyethylene, and polyethylene mixtures with various concentrations of boric acid for separate neutron, separate photon, and simultaneous emissions of neutron and photon by the 252Cf source. Results: HVL values were tabulated for the aforementioned materials for separate neutron, separate photon, and for simultaneous neutron and photon emissions by the 252Cf source. Among the evaluated materials, polyethylene was the most adequate material for neutron shielding. Conclusion: The obtained HVL results for different materials could be used for shielding design around a 252Cf source. According to the comparison of lead with concrete, lead was a suitable material for shielding against the photons emission. On the other hand, concrete with a lower HVL value seemed to be superior for neutron shielding. The combination of several HVL layers of polyethylene and lead could result in proper shielding against neutron and photon. In simultaneous neutron and photon emissions, the emitted neutrons from the source generate secondary photons. The issue led to increase HVL, and could be considered in the protection and shielding against the source.