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Background: Medical x-rays are the largest man-made source of public exposure to ionizing radiation. It is important to avoid conditions where the amount of radiation used is more than that needed for the procedure.

Materials and Methods: The Entrance Skin Exposure (ESE) measurement was conducted for quality control of x-ray machines and survey of operator’s experimental techniques. The ESEs were measured by UNFORS dosimeter for five common types (12 projections) of x-ray procedures in standard man for the 18 public hospitals of Yazd province.

Results: The median, 3^rd quartile, minimum, and maximum values of each ESEs distributions are reported. The 12 histograms are presented showing wide distribution of measured ESE in each examination. The survey results are compared with guide levels that reported by CRCPD or NRPB. The sum of ESEs measurements such as in skull, Th-spine and L-spine are projection out of the guide levels. One of reasons of the wide ESEs distribution is miss unique role in selection of techniques for the same procedure and same patient size by operators in each center and even for one x-ray machine.

Conclusion: The findings support the importance of the on-going quality assurance program to ensure doses are kept to a level consistence with optimum imaging quality. Iran . J. Radiat. Res., 2004 1(4): 199-204

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 ABSTRACT

Background: There are relatively rich uranium mines in regions of Saghand and Bafgh in Yazd province. This survey was carried out to provide a map of ambient gamma radiation of Yazd province and the probable effects of the existence of these mines on background radiation dose rates.

Materials and Methods: The measurements of the outdoor and indoor–environmental exposures (including cosmic and terrestrial components) were accomplished by a portable Geiger Muller detector in the five areas in each of eight big cities of Yazd province.

Results: The average exposure rates of indoor and outdoor ambient of Yazd province were 13.9 ±0.7 µRh^-1 and 11.6 ±0.8 µRh^-1 respectively. The average dose rates in air, resulting from gamma background radiation of indoor and outdoor were 122±6.8 nSvh^-1 and 101.4 ±7.4 nSvh^-1 respectively. The annual average of equivalent dose in air was found to be 1.03 ± 0.05 mSv, and the annual average of effective dose was 0.72 mSv.

Conclusion: The results of this study in comparison with the same measurements in some other cities in Iran such as Isfahan and Tabriz, proves that the existence of uranium mines doesn’t affect gamma background radiation of Yazd province.

 

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  ABSTRACT

  Background: While the benefits of Computed Tomography (CT) are well known in accurate diagnosis, those benefits are not risk free. CT is a device with higher patient dose in comparison with other conventional radiological procedures. Is the reduction of exposures by requiring optimization of CT procedures [a principle concern in radiological protection]? In this study, the radiation dose of conventional and spiral CT were investigated and compared with European Commission Reference Dose Levels (EC RDLs).

  Materials and Methods: The dosimetric quantities proposed in the European Guidelines (EG) for CT are Weighted Computed Tomography Dose Index (CTDI_W) for a single slice for axial scanning or per rotation for helical scanning and Dose-Length Product (DLP) for a complete examination. The patient-related data were collected for brain, neck, chest, abdomen and pelvis examination s in each scanner. For each type of examination, 10 typical patients were randomly included. CTDI with an active length of 10cm was measured in two CT scanners by using UNFORS (Mult-O-Meter 601) in head and body phantom (PMMA) with 16 cm and 32 cm in diameter respectively. Mean values of CTDI_W , DLP and Effective Dose(ED) were estimated for those examinations .

  Results: CTDI_W had a range of 15.8-24.7 mGy for brain, 16.1-30.6mGy for neck, 6.8-9.2 mGy for chest, 6.8-9.8 mGy for abdomen and pelvis. DLP had a range of 246.4-397.7 mGy.cm for brain, 104.6-262.2 mGy.cm for neck, 135-248.4 mGy.cm for chest, 187-298.9 mGy.cm for abdomen and 197.2-319.4 mGy.cm for pelvis. The mean values of effective dose were 0.74 mSv for brain, 0.9 mSv for neck, 3.1 mSv for chest, 3.7 mSv for abdomen and 5 mSv for pelvis.

  Conclusion: The obtained results in this study have shown that CTDI_W and DLP are lower than EC RDLs and other studies, in other words , the performance of all scanners has been satisfactory as far as CTDIw and DLP are concerned. The CTDI_W and DLP in the conventional CT are higher than the spiral CT values . With regard to ALARA principle, for the establishment of reference dose levels, the radiation dose with spiral CT scanners should be taken into account.

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ABSTRACT 

Introduction: Recently uses of medium and high energy x-rays has been increased in Iran and radiotherapy centers along with a variety of accelerators have been installed in some provinces. In the other hand there is no sufficient skill in designing and making radiotherapy treatment rooms. This study was conducted to evaluate the efficacy of different mixtures of barite concrete for shielding the radiotherapy rooms. In this way we emphasized on determining the size and amount of barite aggregations to achieve the maximum radiation attenuation which leads to minimizing wall thickness in treatment room.

Materials and Methods: To increase concrete density, the barite aggregation was added to concrete. Different size variations of barite aggregates mixed with different water/cement ratio were examined. The dimension of cubic concrete specimens for compression strength test was 15×15×15 cm. The rectangular barite concrete blocks with different compressions as used for strength test with cross section of 10×10 cm and thicknesses from 5 to 40 cm were used for radiation attenuation test. For this test concrete specimens were irradiated by gamma beam of ⁶⁰Co (Phoenix Theratron). The transmission radiation through the blocks was measured by a Farmer ionization chamber (FC65P) in Yazd radiotherapy center.

Results: Our findings showed that in all specimens the highest mean compression strength was related to the specimens with equal ratio of fine to coarse barite aggregates but the lowest HVL was obtained from mixtures with fine to coarse ratio of 35/65. The concrete sample with a 0.45 water/cement ratio, 350 kg/m³ cement and equal amounts of fine and coarse barite sands had nearly minimum half value layer(HVL) and maximum compression strength, so this sample was considered as the best barite concrete sample.

Conclusion: Since HVL of the barite concrete specimens with the same compression strength is markedly lower than the conventional concrete and we have a plenty barite mines in our country it is recommended to use barite concrete with the best mixture condition based on our findings for shielding the radiotherapy rooms.

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Background: With the introduction of computed tomography in diagnostic radiology a new and fundamentally different imaging modality has become available. Meanwhile, it is clear that the absorbed doses by the patients during CT were relatively high in comparison with those of other diagnostic radiology techniques. The aim of this survey was to determine the average absorbed dose in Yazd province by CT examinations, and to survey the potential risks per year by these examinations. Materials and Methods: This study was conducted in CT centers of Yazd during 2005-2006. The examination frequencies from 3 CT scanners were collected from all types of examinations. Effective dose were determined by CT Dose program (ImPACT CT patient dosimetry calculator). To use of this software, CTDIair, mAs and the thickness and number of slices in each type of CT examinations should have been measured. CTDIair was measured by pencil diode detector. Results: It was estimated that the annual collective dose and caput dose were about 32.48 Person-Sv and 0.038 mSv, respectively for the Yazd population, which is lower than that reported for other countries. The numbers of examinations per 1000 people of Yazd was 18 which were equal to many other countries such as UK and New Zealand. The mean effective dose of each CT examinations was also lower than that of other countries. Conclusion: Using the ICRP risk factors, radiation dose from CT could be induced to about 1 fatal cancer per year in Yazd. Therefore choosing CT imaging must be completely justified.

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Background: Radiation dose knowledge through Xray examinations and their distribution in Iran provides useful guidance on patient dose reduction. The results of the entrance skin dose (ESDs) of five common radiographies in all radiology centers in Yazd province were reported in our previous study (2003). In the present study we have evaluated the collective effective dose of conventional X-ray examinations, as well as the annual per caput of Yazd population. Materials and Methods: The annual frequencies of 18 different types of conventional radiology examinations during April 2005 to March 2006 were recorded from all 35 radiology centers in Yazd province. The exposure conditions consisted of kVp, mAs, and Focus surface distance (FSD) of the examinations for the mode of exposure in each X-ray unit. 620 ESD were measured by diode dosimeter in 35 hospitals and clinics. The real exposure kVp for each radiology unit was measured by a Molt-O-Meter. The conversion coefficient (effective dose - ESD ratio) for each radiology examination was determined by using SR262 tables. Finally, the patients' effective dose was calculated by multiplying the conversion factor to the ESD. Results: The patients' annual collective effective dose due to the conventional radiology examinations was 31.159 man-Sv (0.03 mSv per inhabitant). The frequency of examinations was 311813 i.e. 0.36 examinations per head of the population for one year. Conclusion: According to our findings, the effective per caput dose seems to be optimally relative to HCL-II countries, which may be due to low mean effective dose that could obscure high examination frequency. The number of radiology conventional examinations and frequency of radiologist per1000 population of Yazd was more and lower than HCL-II countries respectively. Thus the justification of radiography requests in this province must be revised.
Iran. J. Radiat. Res., 2007 4 (4): 195-200

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Background: Indoor radon gas (222Rn) has been recognized as one of the health hazards for human. Air radon comes mainly from basement soil and construction materials. Saghand region with rich uranium mines lies 180 km from Yazd, so the indoor radon concentration can be high. Yazd, with population of about 457000, is the biggest city near Saghand, thus, indoor gamma background radiation of Yazd could be more than the other cities of Yazd province. Materials and Methods: In this study the air radon level of 84 dwellings basement from various regions of Yazd were measured during the year 2007. To do so, a portable radon gas surveyor was used which is an active measurement method. Using this device, α radiation of each basement was measured by a solid state detector for 24 hours. Results: Radon concentrations of the basements were between 5.55 to 747.4 Bq/m3 with mean of 137.36 Bq/m3. The mean radon concentration wasn't significantly different from the EPA guide line that is mitigation recommendations level (148 Bq/m3). However, more than 30% of the basements had radon concentration more than EPA guide line. Conclusion: Using good air conditioning system in the dwelling basements is suggested. Iran. J. Radiat. Res., 2008 6 (3): 141-144

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Background: The number of interventional cardiology (IC) procedures has increased rapidly. coronary angiography (CA) and percutaneous transluminal coronary angioplasty (PTCA) are now widely performed as a matter of routine, and they are considered safe procedures for experienced cardiologists. However, it is also known that these procedures are associated with high radiation doses due to long fluoroscopy time (T), and large number of cineradiography frames (F). These levels of radiation may even lead to radiation skin injuries under certain conditions. Materials and Methods: A detailed study of radiation doses received by 168 patients who underwent coronary angiography (CA), and 84 patients who underwent percutaneous transluminal coronary angioplasty (PTCA) using 3 angiography X-ray systems in two hospitals of Yazd-Iran is presented. An air kerma-area product (KAP) meter was used for patient dosimetry. KAP, fluoroscopy time and total number cine frames for CA and PTCA procedures were recorded for each patient. Results: Mean ± SD of KAP in CA and PTCA were 33 Gy.cm2 ± 18.8 Gy.cm2 and 80.3 Gy.cm2 ± 65.6 Gy.cm2 respectively. The comparison showed that CA KAP (33Gy.cm2), fluoroscopy time (2.7±2.4min), and cine frames number (571±149) except of on case, were lower than (P<0.001) the results of other studies and mean KAP due to PTCA procedures, except for three cases, were not significatly different from the other references’ results. Conclusion: The high level expert cardiologists couldn't have a significant effect on the decrease of patient dose since they should also teach angiography examinations to medicine students. With increasing patient BMI the value of KAP increased, but the fluoroscopy time and cineframes number did not change significantly. In addition, the results showed that the use of flat panel detector was not sufficient for decreasing patient dose, and system's adjustment was more important. Iran. J. Radiat. Res., 2009 6 (4): 167-172

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Background: Since 1996 the assessment of environmental gamma radiation dose in residential areas of Iranian towns and cities has been accomplished for 10 counties. As a practical method and based on the results of a pilot study, in order to attribute the final results to the whole residential area of a town five stations were selected for every town. The location of individual station was studied closely to comply with recommended conditions in the literature. Materials and Methods: RDS-110 was employed to measure gamma dose rate for one hour. Average annual dose rates plus conversion coefficients were employed to estimate gonad, bone marrow, equivalent and effective dose. Result: Minimum and maximum annual bone marrow and gonad dose equivalent attributed to environmental gamma are 0.24 mSvy-1 (for both tissues) and 1.44 and 1.46 mSvy-1, respectively. Conclusion: Average gonad and bone marrow doses for North Khorasan, Boshehr and Hormozgan provinces were less than the corresponding values for normal area. Iran. J. Radiat. Res., 2009 7 (1): 41-47