International Journal of Radiation Research
Year:2009 | Volume:6 | Issue:4|Papers Count:8

Background: All aerobically growing organisms suffer from exposure to oxidative stress, caused by partially reduced forms of molecular oxygen, known as reactive oxygen species (ROS). These are highly reactive and capable of damaging cellular constituents such as DNA, lipids and proteins. Consequently, cells from many different organisms have evolved mechanisms to protect their components against ROS. It is known to have some genes for resistance to heavy metals and ionizing radiation (IR). Materials and Methods: Saccharomyces cerevisiae is an ideal model organism for deducing biological processes in human cells. In this work, cell viability and gene expression was investigated in yeasts treated with IR, HgCl2, and IR combined with HgCl2. Cell viability was measured by colony forming unit (CFU) method in an YPD medium. Gene expression was analyzed by the Real-time PCR. Results: The viability was lower at the higher dose. At a dose above a certain level, the viability came down to zero. The combined treatment decreased the viability, as well. Metal resistance genes were expressed in the cells treated with HgCl2. In a similar way, irradiation also triggered the expression of some radiation resistance genes. YCF and YAP genes were induced consecutively with the HgCl2 concentration, and also with a higher total dose under a lower dose rate condition. These two genes were, however, expressed differently under the 0.2 mM HgCl2 treatment condition. In the cells treated with 0.1-0.2 mM HgCl2, the viability was higher than with any other concentrations. Conclusion: The results demonstrated that the higher dose induced more expression of oxidative stress resistance genes related to cell survival mechanism. Combined treatment of radiation with mercury chloride resulted in synergistic effects leading to a higher expression of the genes than treatment of a single stressor alone.

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 significantly 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.

Background: Butterworth, Gaussian, Hamming, Hanning, and Parzen are commonly used SPECT filters during filtered back-projection (FBP) reconstruction, which greatly affect the quality and size accuracy of image. Materials and Methods: This study involved a cardiac phantom in which 1.10 cm thick cold defect was inserted into its myocardium wall and filled with 4.0 mCi/ml (0.148 MBq/ml) 99mTc concentration. The cardiac insert was then put into a cylindrical tank which was filled with 1.2 mCi/ml (0.044 MBq/ml) 99mTc concentration as background. 272 combinations of filter parameters were selected from those filters and applied on image. The measurements of count in myocardium, background, and defect regions of interest (ROI) were performed on each filtered image. Those measurements were then used to calculate contrast, signal-to-noise ratio (SNR), and defect size. For every filter, each criterion was graded (1 to 100) and then summed at their specific setting for total comparison. Results: The results show that, the different filter types produced myocardial image with different contrast, SNR, and defect size. For contrast and SNR, Gaussian filter was the best, while Parzen filter was the best in producing accurate defect size. However, Butterworth filter was found the best for trade off between contrast, SNR, and defect size accuracy.Conclusion: Selection of filter should consider the type of analysis, whether qualitatively or quantitatively. Qualitative analysis depends on image quality which is denoted by high contrast and SNR, thus Gaussian filter was suggested. Instead, the Butterworth filter was suggested for quantitative analysis as it is greatly dependent on both, image quality and size accuracy. 

Background: Designing and shielding of an appropriate radiography room has been one of the major concerns of radiation scientists since the first decade after the invention of X-rays. Recently, report No.147 of National Council on Radiation Protection and Measurements (NCRP) has been published. In this study the researchers have investigated the effect of new report recommendation on primary and secondary barriers thicknesses in comparison to NCRP 49, and 116 recommendations. Materials and Methods: To calculate the walls thickness of a conventional radiography room, the workload of a radiography room of a university hospital was determined by recording the number of exposures, mAs and kVp for each patient during six months. Three types of calculations were done: (1) Using NCRP 49 formulations and dose limits (2) Using the NCRP 49 formulations and NCRP116 dose limits and (3) Using the NCRP 147 recommendations. Results: The estimated workload was 172 mA min wk-1 for the studied radiography room which was slightly lower than the workload recommended by NCRP147. The results showed that using the NCRP49 formulation and NCRP116 dose limits, the barriers thickness increases substantially. Moreover, the dose limits were lower in NCRP 147, using the third method. The primary barrier thickness is decreased considerably in comparison to two other methods. For the secondary barrier the results of the two methods (1) and (3) did not differ and remained the same.Conclusion: Application of NCRP 49 and NCRP116 dose limits for radiography room shielding (second method) overestimated the primary and secondary barriers thickness, significantly. But, applying NCRP 147, not only the new dose limits were considered, but also the cost of primary barrier construction was reduced.

Background: Best dose distribution in target volume and control of Organ at Risk (OAR) dose are the two main goals in brachytherapy. Materials and Methods: In this study in vivo dosimetry in 4 rectal points was performed by Transillumination Dosimeter (TLD) s and the measured doses were compared in different patients. One point was reported to have the maximum dose in each patient and the very dose was considered as rectal dose according to ICRU-38 prescription; however, the next higher dose was also considered the same as the highest point when the difference was not more than 10% of the highest value. Results: In more than 50% of the cases the 1st and 2nd highest points were in the same range with less than 10% variation. There were 3 points in approximately equal dose in 7% of cases. Conclusion: These findings are challenging with the ICRU-38 recommendations reporting the existence of a sole maximum rectal dose. So it seems wise to consider an isodose plate of maximum doses instead of one point only.

Background: Solid targets that consist of powder and electrodeposited targets are used commonly to produce radionuclides by accelerators. Since silver is easily electrodeposited in cyanide baths and has a very excellent thermal conductivity, the electrodeposited target is preferable to produce 109Cd. To avoid cracking or peeling of the target during bombardment, it should have a level surface and a good adhesion to substrate. Hence, suitable targetry has extraordinary importance for the interested radionuclide production. Materials and Methods: Excitation function of cadmium-109 via natAg (p,n)109Cd reaction was investigated by using ALICE-91 code. The required thickness of the silver deposit was calculated by SRIM code. Theoretical yield was calculated by means of Simpson numerical integral method. Silver was electrodeposited on copper backing by the cyanide bath. The prepared targets were examined with morphology and thermal shock tests. Results: The most favorable beam energy was determined as 15 MeV. The desired thickness was determined to be up to 48 mm; the theoretical calculated yield was 2.69 mCi/mA·h. Scanning electron microscope (SEM) photomicrographs and thermal shock tests represented excellent quality of the electrodeposited target. Conclusion: The present study suggested a good potentiality of cadmium-109 production by induced proton on electrodeposited silver targets.

Background: Although ionizing radiation is widely used to diagnose many diseases, the relevant hazards are known to be as an important limitation of its application. It is believed that the awareness of ionizing radiation dose values is one of the main stages in patient's radiation protection. The purpose of this study has been to investigate the level of physicians' knowledge about radiation doses received by patients in radiological examinations. Materials and Methods: A questionnaire was designed and the most commonly requested radiological investigations were listed. Participants (155 physicians) were asked to identify the average dose of radiation received by patients when they underwent a posterior-anterior hand X-ray. Then, it was utilized to represent a single dose of radiation, and physicians were asked to estimate the equivalent doses of radiation for other radiological examinations. Several questions were also included about dose measurement's units and low exposure risk investigations. Results: The results indicated that only 58.3% of physicians know the units of radiation absorb dose measurement units. Most of them could not correctly estimate the amount of radiation dose received by patients in a routine radiography of hand and majority of them underestimated the radiation dose of other radiological examinations. Conclusion: Despite of passing medical physics course, during studentship, it does seem that most of medical doctors did not have enough knowledge about the amount of radiation received by patients led for diagnostic radiology investigations.

Premature Chromosome Condensation (PCC) appears to have a possible utility for biological dosimetry purposes. The PCC technique may be adapted for cases of suspicion of overexposure where sampling is performed at least one day after an accident. For this purpose, human blood samples were exposed in vitro to 60Co up to 10 Gy and the PCC technique was performed immediately after irradiation. Analysis of excess PCC fragments distribution showed an over dispersion and the dose- effect relationship was best characterized by linear regression.