Voxel dosimetry: Comparison of MCNPX and DOSXYZnrc Monte Carlo codes in patient specific phantom calculations.

INTRODUCTION: Dose evaluation with two Monte Carlo codes using patient specific voxel phantom is presented in this paper. We employ both MCNPX and DOSXYZnrc to perform dosimetry for mathematical voxel phantoms generated by our in-house developed voxel phantom generator and EGSnrc/CTCreate respectively. MATERIAL AND METHOD: Our case study was a 2.5 × 2.4 × 2.4 cm3 tumor in the middle lobe of right lung of a male patient exposed to 6MV parallel beam. In order to compare these Monte Carlo codes with together gross tumor volume (GTV) and organ at risks (OAR) doses and dose volume histograms (DVH) were calculated. RESULTS: Comparing the mean absorbed dose results (in Gy) from both codes indicates that gross tumor volume, heart and spinal cord have 2% to 10% difference. The 10% difference between the codes were from the spinal cord region where was not in the therapy beam and it just received the scatter radiation. The dose volume DVH obtained from DOSXYZnrc results demonstrate a milder slope compared with MCNPX DVHs. CONCLUSION: It was revealed that MCNPX has some advantages in comparison to DOSXYZnrc, but it is important to consider that for equal precision in voxel dosimetry calculation, DOSXYZnrc runs faster than MCNPX and it is a great advantage.

Application of polystyrene films for indoor radon dosimetry as SSNTD.

In this study, the sensitivities and calibration factors of polystyrene (PS) to (220)Rn and (222)Rn have been investigated. The sensitivity of compact disks (CD/DVD) as thick polycarbonates (PC) to (220)Rn and (222)Rn has been also obtained by applying a new etching condition. Five different brands of X-ray radiology and MRI films with polystyrene base and four brands of CD/DVDs have been studied to assess their applicability as a passive detector for indoor radon monitoring. The comparison between the sensitivities of PS samples, CD/DVDs (as thick PC) and Lexan PC to (222)Rn and (220)Rn shows an improved sensitivity of PS over conventional PC currently being used as solid state nuclear track detectors (SSNTD). The sensitivity of X-ray radiology PS films to (222)Rn and (220)Rn was found to be 8.77±0.591 and 0.028±0.006 (cm(-2)kBq(-1)d(-1)m(3)). The sensitivities of MRI PS films to Rn-222 and Rn-220 was found to be 12.2±1.25 and 0.360±0.090 (cm(-2)kBq(-1)d(-1)m(3)). The CD/DVD PC found to have a sensitivity of 0.178±0.013 and 0.0024±0.00013 (cm(-2)kBq(-1)d(-1)m(3)) to (222)Rn and (220)Rn respectively.

The design of long-term air quality monitoring networks in urban areas using a spatiotemporal approach.

The implementation and maintenance of an air pollution monitoring program can be expensive and time consuming, especially when the aim is for long-term monitoring over a significant area. Consequently, it is essential that sites are optimized to provide the best representative cover while minimizing costs. In the past, there has been a tendency to locate sampling stations at pollution hot-spots. While this is acceptable for determining a maximum potential exposure or identifying the extent of a risk, there are limitations to this approach when assessing the potential impact of any future abatement strategies or determining the level of exposure outside the vicinity. This paper presents an approach in which representative air quality assessments can be undertaken for an urban area using the minimum number of measurement sites. A novel methodology is described that involves site selection to capture the maximum variance in measured pollutants, while minimizing spatiotemporal autocorrelation between the selected sites. A case study is presented for Yazd, Iran. Overall, the results show that the proposed methodology can be effective and enable the long-term monitoring of air pollution to be undertaken on a cost-effective basis in urban areas. In addition, there is the potential for the methodology to be utilized for other forms of pollution (e.g., water, soil, and noise).

U-series concentration in surface and ground water resources of Ardabil province.

Hundred and sixteen water resources including springs, wells, rivers and lakes in Ardabil province, northwest of Iran, were sampled and analyzed. The analysis included chemical analyses, (222)Rn and (226)Ra levels as well as total Uranium contents. (222)Rn levels were determined only for hot springs. The concentrations of Radium and Uranium in all water resources of Ardabil province were determined by the collector chamber and fluorimetric methods, respectively. The Radium and Uranium concentrations ranged from 2.0 to 300 mBq L(-1) and from 1.4 to 280 ppb, respectively. Furthermore, the annual effective dose varied between 8 and 47 microS y(-1). The reason for variations of Radium and Uranium concentration is the diverse geological structures in Ardabil province. The aim of this study was to determine the level of natural radioactivity in all water resources of the Ardabil province and whether this radiation causes any danger to health. The hot springs were found to have high level of activities and some water resources in Meshkin-Shahr city had the highest activities among other cities in Ardabil province.

Indoor radon monitoring in Northern Iran using passive and active measurements.

In this work we present the results of a 2-year survey of indoor radon variations in four cities of Lahijan, Ardabil, Sar-Ein and Namin in North and Northwest Iran. We used both passive and active measurements by solid state nuclear track detectors (SSNTDs) with CR-39 polycarbonate and PRASSI Portable radon Gas Surveyor. A total of 1124 samplers in Lahijan, Ardabil, Sar-Ein and Namin were installed. Sampling frequency was seasonal and sampling locations were randomly chosen based on dwelling structures, floors, geological formations, elevation and temperature variation parameters. For quality assurance, 281 active measurements and double sampling were carried out. Based on our results and the results of previous surveys, Ardabil and Lahijan have the second and third highest radon concentration in Iran, respectively (Ramsar is first). The average radon concentration during the year in Lahijan, Ardabil, Sar-Ein and Namin were 163, 240, 160 and 144 Bq/m(3) with medians of 160, 168, 124 and 133 Bq/m(3), respectively. These concentrations give rise to annual effective doses of 3.43 mSv/y for Lahijan and 5.00 mSv/y for Ardabil. The maximum recorded concentration was 2386 Bq/m(3) during winter in Ardabil and the minimum concentration was 55 Bq/m(3) during spring in Lahijan. Relationships between radon concentration and building materials and room ventilation were also studied. The dosimetry calculations showed that these four cities could be categorized as average natural radiation zones. The correlation coefficients relating warm and cold season radon variation data were obtained.