فهرست مطالب
International Journal of Radiation Research
Volume:15 Issue: 2, Apr 2017
- تاریخ انتشار: 1396/04/04
- تعداد عناوین: 12
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Pages 129-139BackgroundCell ability to recover from radiation damage is of great relevance in cancer treatment. It is often believed that the inhibition of cell ability to the liquid holding recovery (LHR) may be an indicator of the overall suppression of cell ability to recover from potentially lethal radiation damage. However, the literature contains no experimental evidence whether the LHR inhibition may always serve as marker of the significant increase in cell sensitivity to damaging agents.Materials And MethodsIn experiments described here the yeast cells were used as a model for eukaryotic cells. The dose-response curves and recovery kinetics were determined by colony assay after simultaneous treatment of heat with ionizing or UV radiations as well as after the simultaneous action of ionizing radiation and cisplatin. The cell survival was estimated by both microscopic method and colony forming ability.ResultsIt is demonstrated that the recovery may take place on nutrient media. The complete inhibition of cell recovery after simultaneous heat treatment with ionizing radiation or UV light is accompanied with the significant increase in cell sensitivity to these agents, the actual increase being more appreciable than that expected after the inhibition of the LHR only. This rule is not universal as it was demonstrated for diploid yeast cells exposed to ionizing radiation and cisplatin.ConclusionThe LHR takes place on nutrient media during the delay of the first postirradiation division. The LHR inhibition may not always indicate the suppression of other dark recovery processes and the corresponding increase in cell radiosensitivity.Keywords: Yeast cells, ionizing radiation, UV light, hyperthermia, cisplatin, liquid-holding recovery
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Pages 141-148BackgroundRadiotherapy is an effective and important therapeutic method for breast cancer, but at the same time it has a radiation-induced bystander effect on normal tissue around the tumor. Repair of double-strand breaks (DSBs) by normal cells can reduce the extent of damage caused by this effect. Caveolin-1 (Cav-1) is an important regulatory molecule in cell signal transduction. However, the response of normal human mammary epithelial cells following low dose radiation (LDR)- induced DSBs and the role of Cav-1 in the repair of the DSBs are not clear. The present study examined the DNA damage repair mechanism triggered by LDR in human mammary epithelial cells.Materials And MethodsHuman mammary epithelial (MCF10A) and Cav-1 haplo-insufficiency (MCF10A-ST1) cells were irradiated with LDR gamma rays and the effect of this radiation on cell proliferation was determined by cytometric method. Western blot analysis was then used to measure the expression levels of different proteins associated with cell proliferation and DNA repair.ResultsLDR enhanced the radiation responsiveness of MCF10A cells in a dose- and time-dependent manner. At a dose of 100 cGy, LDR increased the expression levels of several proteins involved in DNA repair pathways, such as ATM, p53, DNA-PKcs and also activated Cav-1-mediated cell proliferation and survival pathways, such as the MAPK and AKT pathways. The expression of the various DNA repair related proteins was changed after down-regulating the Cav-1 expression.ConclusionLDR could increase the radiation responsiveness of human mammary epithelial cells through activating the DNA repair pathways, including both HR and NHEJ pathways, as well as triggering the cell proliferation and survival pathways, both of which required Cav-1.Keywords: LDR, DNA repair, Caveolin-1, human mammary epithelial cells, NHEJ, HR
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Pages 149-155BackgroundMedical diagnostic procedures such as X-ray and computed Tomography (CT) scan account for considerable percent of patient's exposure to ionizing radiation. The exposure of cells to Ionization radiation results in induction of DNA damage and chromosomal aberrations. Contrast media (CM) are widely used in diagnostic radiology and CT scan. The aim of this study was to study adverse genetic effects of combined administration of non ionic contrast media and low dose X-rays in peripheral blood Lymphocytes of patients following abdominal CT scan.Materials And MethodsA total of 55 patients underwent abdominal CT scan with injection of non ionic contrast media (30 patients with omnipaque 300 mg/ml and 25 patients with visipaque 270 mg/ml) as well as 13 patients undergoing abdominal CT scan (without contrast), selected as control group, were enrolled in this study. Peripheral blood leukocytes were obtained in heparin containing tubes and cultured for the micronucleus test, or were directly used for apoptosis and DNA damage with the neutral comet assay.ResultsThe frequency of micronuclei, apoptosis and percentage of DNA damage was increased in most patients after the injection of contrast media, significantly different from the control group as compared with the samples obtained before and after injection of contrast media (PConclusionThe present study suggest that non ionic contrast media (omnipaque 300 mg/ml and visipaque 270 mg/ml) may cause a significant increase of cytogenetic damage in peripheral blood lymphocytes. This effect might be caused by the enhancement of radiation dose by CM that eventually may lead to the manifestation of ill health such as cancer.Keywords: Contrast media, micronuclei, apoptosis, DNA damage, computed tomography, lymphocytes
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Pages 157-165BackgroundThis study was conducted to assess the accuracy of dose calculation near the air-phantom interface of a heterogeneous phantom for Acuros XB (AXB) and Anisotropic Analytical Algorithm (AAA) algorithm of a 6-MV flattening-filter-free beam, compared with film measurements.Materials And MethodsA phantom included air gap was specially manufactured for this study. In order to evaluate the dose near air gap-phantom interface, Eclipse treatment planning system equipped both AXB and AAA was used for the dose calculations. Measurements in this region were performed with radiochromic film. The central-axis dose (CAD) and off-axis dose (OAD) between calculations and measurements were analyzed for various field sizes and air gaps. The root-mean-square-error (RMSE) was used to evaluate the difference between the calculated and measured OAD. In order to quantify agreement between the calculated and measured dose distributions, the gamma analysis was performed with the 2%/2 mm and 3%/3 mm criteria.ResultsFor all fields traveling through 1 and 3 cm air gap, the maximum difference in the calculated CAD was -5.3% for AXB and 214.8% for AAA, compared to the measured CAD. For the RMSE between the calculated and measured OAD, the calculated OAD using AXB showed interval in the RMSE (from 4.4 to 12.7) while using AAA indicated broad (from 7.7 to 101.0). In addition, the gamma passing rates showed that AXB was higher agreement than AAA.ConclusionThis study demonstrated that AXB was more accurate in heterogeneous media near air-phantom interface than AAA when comparing the measured data.Keywords: Acuros XB, anisotropic analytical algorithm, heterogeneous media, FFF, interface
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Pages 167-175BackgroundWe used a MapCHECK software-based dimensional dose distribution comparison method capable of evaluating point-to-point geometrical dose differences in volume to determine whether doses obtained from an enhanced computed tomography (CT)-based treatment plan, which better defines the target regions and organs at risk, differs from doses obtained from plain CT and then evaluated the feasibility of treatment planning via enhanced CT.Materials And MethodsForty-three randomly selected patients underwent plain and subsequent enhanced CT with the same settings. Treatment plans developed for the two scans were identical in terms of planning parameters (e.g., isocentre, gantry angle, segments) and monitor units (MU) used for dose calculation. Horizontal and vertical dose distribution planes across the same isocentre were selected from two types of plan; a two-dimensional dose distribution analysis was used to determine the Distance-To-Agree (DTA) pass ratios of corresponding dose distribution planes.ResultsObtained doses at the head and neck (H&N) and pelvic sites did not differ greatly between enhanced and plain CT. However, enhanced CT significantly influenced doses to the lower thoracic oesophagus. A corrected pass ratio that was achieved by non-pass points in lower isodose areas excluded from the statistical analysis had better clinical outcome.ConclusionRadiation plans with multi-fields and multi-angles can reduce the influence of enhanced CT on torso cases and may even negate its influence on H&N cases. Enhanced CT can be directly used for planning unless the target region contains the lower oesophagus and its surrounding blood vessel whose high density requires correction.Keywords: Treatment planning, enhanced CT, plain CT, dimensional dose distribution, dose comparison
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Pages 177-183BackgroundTo compare the dosimetric coverage of the planning target volume (PTV) and the dose delivered to the main Organs at Risk (OARs) in 5 and 7-field techniques of Intensity Modulated Radiation Therapy (IMRT) in patients with local prostate cancer.Materials And MethodsTwelve patients with local prostate cancer underwent 5 and 7-field IMRT planning. The delivery of IMRT was carried out using the sliding technique. The dose coverage for PTV was designated to ≥98% of the PTV covered by 95% of the prescribed dose. Dose conformity was evaluated by comparing the volume of nontarget tissue receiving maximum, and average of the prescribed dose and the dose of 33%, 50%, and 66% of the volumes on both planning sets. For target, this evaluation was made with comparing the Conformity Index (CI) and Inhomogeneity Index (HI). In addition, we compared the monitor units used for dose delivery in both planning techniques.ResultsAll the 5 and 7-field IMRT plans differed slightly in the measured parameters, and none of them have statistically significant differences with each other except for the monitor units where significant differences were observed in favor of the 5-field IMRT plans (p=0.000). In all of the 5-field IMRT plans the mean dose delivered to OARs were very similar or less than that of the 7-field plans.ConclusionIn comparison to the 7-field technique, the 5-field IMRT technique has resulted in improved IMRT dose conformity, homogeneity, and lesser MUs used for radiation therapy. However, this difference was not significant.Keywords: IMRT, dose conformity, MUs, prostate cancer
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Pages 185-196BackgroundThere are various methods to read out responses of a polymer-gel dosimeter, among which the Magnetic Resonance Imaging (MRI) technique is the most common one. Optimizing imaging protocols can have significant effect on the sensitivity and the dose resolution of polymer gel dosimeters. This study has investigated the effects of the number of echoes (NOE) and the echo time spacing (ES) parameters on the response of the PAGATUG polymer gel dosimeter.Materials And MethodsThe polymer gel dosimeters were produced under the normal atmospheric condition, then irradiated using a 60Co clinical radiation source. The polymer gel dosimeters were imaged using MRI technique with different imaging protocols. Afterwards, the effects of the ES and the NOE on the R2-sensitivity and the dose resolution of PAGATUG polymer gel dosimeter have been investigated.ResultsResults showed that the sensitivity decreased with increasing NOE. However, it was found that the resolution got better with increasing NOE. Furthermore, the investigation of signal intensity decay curve showed that the R2 values in NOE less than 5 was less reliable. According to the results, no significant difference were found between the sensitivities of the polymer gel dosimeters which were imaged with different ESs, except for ES=22 ms. However, dose resolution suffered from ES increasing.ConclusionDosimetric parameters of PAGATUG polymer gel dosimeter reaches to their optimum values by imaging with ES=25ms and NOE=10.Keywords: Polymer gel dosimeter, PAGATUG, MRI, Number of echoes, Echo time spacing
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Pages 197-205BackgroundRadiation doses associated with the conventional dental radiographies are relatively low, but their number is high. Therefore, justification is necessary to ensure that radiation doses to patients, particularly children, are kept as low as reasonably achievable.Materials And MethodsThe exposure factors applied for real patients in four age groups (5, 10, 15-year-old and adult) were obtained for conventional dental radiographies, periapical, bitewing, and panoramic. The dose-area product (DAP) values were measured for every dental radiographies. The risk of exposure-induced cancer death (REID) was estimated for every dental radiographies in different age groups and in both genders.ResultsThe range of the REID values in periapical radiography were 1.3 to 20.9 per ten million for male patients, and 1.6 to 28.3 per ten million for female patients in different age groups. The range of REID values in bitewing radiography were 1.5 to 11.2 per ten million for male, and 1.9 to 13.2, per ten million for female in different age groups. The mean of REID values in panoramic radiography were 7.32, 4.70, 3.55, and 2.1 per ten million for male patients in 5-, 10-, and 15-year-old and adult age groups, respectively, and were 9.43, 5.86, 4.25 and 2.41 per ten million for female patients in 5, 10, 15-year-old and adult age groups, respectively.ConclusionIn accordance with the results of the present study, the overall risk of cancer from radiation in children was more than adult and in female patients is more than male patients in dental X-ray examinations.Keywords: Dental radiography, organ doses, effective dose, radiation risk
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Pages 207-211BackgroundHair dyes are the important materials widely used by various peoples in Iraq and other countries. The present work investigates the presence of the effective radium content and radon exhalation rate in hair dyes samples.Materials And MethodsTwenty hair dyes samples were collected from Iraqi markets. Sealed can technique using LR-115 type II plastic track detector s has been used in order to measure the effective radium content and radon exhalation rate.ResultsThe average values of the effective radium content ranges were from 2.30±0.179 Bq/kg to 3.07±0.254Bq/kg and the average values of radon exhalation rate range of 0.282±0.019 mBq/m2.day to 0.369±0.026 mBq/m2.day.ConclusionThe results coincide with the recommended OECD and ICRP's action level. In addition a good correlation was found between the effective radium content and radon exhalation rate in hair dyes samples.Keywords: Hair dyes samples, Radon exhalation rate, effective radium content, Sealed can technique, LR- 115 type II
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Pages 213-218Background: Radiotherapy is an important factor which results in increase of anastomosis leakage. Diverting loop ileostomy has been usually performed after colorectal anastomosis with history of neo-adjuvant radiotherapy to decrease the chance of leakage. Considering this effect, we assessed the feasibility and outcome of human amniotic membrane in rectal anastomosis in dogs previously treated by high-dose radiotherapy.Materials And MethodsTwelve cross-breed male dogs with the age of 6-8 months and weighting 10-15 kg were randomly divided into four groups. Groups 1 and 2 received radiotherapy and 4 weeks later, single layer end to end anastomosis was performed for all the dogs; also, diverting loop ileostomy was placed in groups 1 and 3. Four weeks later, the anastomosis site was resected and sent for pathologic wound healing scoring. Data were analyzed by SPSS 16 software using Mann- Whitney test.ResultsTwo dogs (of group 1 and 2) died of peritonitis due to anastomosis leakage during the 2nd post operation week. There was no statistically significant difference in wound healing between the case and control groups (P-Value: 0.01).ConclusionHAM had a protective role in colorectal anastomosis after neo-adjuvant radiation in cases without loop diverting ileostomy. It can be concluded that HAM placement is a feasible technique instead of diverting loop ileostomy in cases with neo-adjuvant radiotherapy and also in the benign colorectal diseases with high risk anastomoses.Keywords: Human amniotic membrane, radiation therapy, anastomosis leakage, ileostomy
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Pages 219-224BackgroundMeasurement of the radiation dose distribution is important in assessing the health risk a population and serve as reference in documenting changes to environmental radioactivity in soil due to man-made activities.Materials And MethodsThe activity concentration of 238U, 232Th and 40K in soil samples obtained from different locations in Ajaokuta Local Government area was measured using Hyper Pure germanium Detection System (HPGe).ResultsThe calculated average concentration of the radionuclides ranged from 12 ± 1 Bqkg-1 to 59 ± 2 Bqkg-1 for 238U, 14 ± 1 Bqkg-1 to 78 ± 5 Bqkg-1 for 232Th and 49 ± 2 Bqkg-1 to 1272 ± 23 Bqkg-1 for 40K. In order to evaluate the radiological hazards due to natural radionuclides within Ajaokuta, the absorbed dose rate, gamma index, radium equivalent and excess lifetime cancer risk were estimated. According to measured data from the top soil (0-10 cm), the estimated radium equivalent (Raeq) ranges from 55.7 Bqkg-1 at Steel Complex to 253.3 Bqkg-1 obtained from Forest samples.ConclusionThe mean absorbed dose rate, annual effective dose and gamma radiation index evaluated were 66.2 nGyh-1, 81.2 µSvy-1 and 1.05 respectively which are higher than the recommended limit for normal background radiation. Thus, we conclude that people living in these locations may be exposed to higher radiation.Keywords: Radiation hazard, gamma index, excess lifetime cancer risk, soil, Ajaokuta
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Pages 225-228BackgroundThe activity concentrations of 226Ra, 232Th and 40K in sand used as building material in Weifang of China were investigated for evaluating the radiation hazard.Materials And MethodsSand samples were collected from Weifang and their radioactivity levels were measured using gamma-ray spectrometry. The radiation hazard for residents was assessed by radium equivalent activity (Raeq), indoor air absorbed dose rate (D), annual effective dose (AED) and excess lifetime cancer risk (ELCR).ResultsThe activity concentrations of 226Ra, 232Th and 40K ranged from 11.7 to 23.0, 33.6 to 126.1 and 353.2 to 924.8 Bq kg−1 with averages of 15.5, 70.3 and 802.9 Bq kg-1, respectively. All Raeq values were lower than the limit of 370 Bq kg-1. The mean value of D was higher than the world population-weighted average of 84 nGy h-1, while the mean AED and ELCR values were below the internationally accepted values.ConclusionsThe use of sand in construction of dwellings is considered to be safe for inhabitants.Keywords: Gamma, ray spectroscopy, natural radioactivity, radiation hazard, excess lifetime cancer risk, sand