جستجوی مقالات مرتبط با کلیدواژه "attenuation" در نشریات گروه "پزشکی"

Oxidative stress may be a causative factor for bisphenol A (BPA) -induced hepatotoxicity. Glutamine (GM) is an amino acid with the ability to inhibit oxidative stress. 

This study evaluated the ability of GM to prevent BPA-induced hepatotoxicity in rats. 

Adult Wistar rats of both sexes (n=30) were used. The rats were randomly grouped into six of five rats each. Groups A (Control), B, and C were treated with normal saline (0.2 mL), GM (80 mg/kg), and BPA (50 mg/kg), respectively for 60 days. Groups D-F were treated with GM (20 mg/kg)+BPA (50 mg/kg), GM (40 mg/kg)+BPA (50 mg/kg), and GM (80 mg/kg)+BPA (50 mg/kg), respectively for 60 days. After treatment, blood and liver samples were obtained for biochemical and histological assessments, respectively. 

Significantly (P<0.01) decreased body weight and significantly (P<0.01) increased liver weight occurred in the BPA-administered group when compared to the control group. The BPA-administered group showed significantly (P<0.001) elevated serum total bilirubin, lactate dehydrogenase, aminotransferases, conjugated bilirubin, gamma-glutamyl transferase, alkaline phosphatase, and liver malondialdehyde concentrations when compared to the control group. Significantly (P<0.001) decreased liver superoxide dismutase, glutathione peroxidase, catalase, and glutathione levels occurred in the PBA-administered group when compared to the control group. BPA caused hepatocyte necrosis, sinusoids, and central vein congestion. BPA-induced hepatotoxicity was reversed by GM; 20 mg/kg (P<0.05), 40 mg/kg (P<0.01), and 80 mg/kg (P<0.001) in a dose-related fashion when compared to BPA. 

GM may be effective against BPA-associated hepatotoxicity.

We aimed to investigate the efficacy of Hounsfield unit (HU) attenuation measured on computed tomography (CT) as a non-invasive method for pleural effusion characterization.

Patients with pleural effusion who underwent thoracic CT imaging and thoracentesis within a maximum of three days were included in this retrospective study (15 transudate and 36 exudate). By drawing a circular region of interest (ROI) on the section with the thickest pleural effusion in terms of anteroposterior diameter in the upper-medial-lower zone on axial images, a total of three HU values, one from each level, were averaged. An independent t-test was applied to the CT attenuation (HU) values for the transudate-exudate differentiation. A receiver operating characteristic (ROC) analysis was then made.

The mean attenuation±standard deviation (minimum-maximum) value for the patients with transudate was 2.17±3.76 ((-7.5)-7.5) HU, whereas the mean HU value for the patients with exudate was 8.38±6.2 ((-6)-22). The independent t test made for the transudate-exudate differentiation revealed a statistically significant difference (P=0.001). In the ROC analysis carried out to determine the cut-off value of the attenuation value of pleural effusion in the transudate-exudate differentiation, the area under the curve was found to be 82.8%. When the cut-off value was taken as 2.75HU for the area under the curve, sensitivity was found to be 84%, and specificity was 60%.

Although CT-HU values are statistically significant in the differential diagnosis of transudate-exudate, there is still a need to establish a correlation with other tomographic findings and clinical laboratory findings.

The most successful and effective preventive measure against infection from a particular disease is to get vaccinated. Traditional vaccines use a dead or a weakened pathogenic microbe or a toxin from a pathogen. The introduction of an attenuated or dead pathogen into a healthy individual generates an immune response. Vaccines aid in creating a memory of the antigenic specificity of disease in the individual, thus immunizing the individual against that particular disease for a long period. Therefore, getting vaccinated for a disease is the best measure one can take, especially for military forces. Due to the circumstantial juxtaposition of a soldier in harsh environments while serving his nation with little to no amenities, the threat of a biological agent increases significantly. Thus, the maintenance of hygiene and immunity is of utmost importance in the military to prevent any setback in the line of duty. Some vaccines do require booster doses to retain the memory of antigenic specificity. Various techniques have been developed or are under development to produce effective vaccines for several diseases. A key development in traditional vaccines is the reduction of booster doses required, as well as the reduction of side effects. Any technique used to produce vaccines has to ensure the provision of long-term immunity to the individual, no side effects on the individual due to the vaccine, no relapse or reversion of pathogenicity, and induction of an immune response at a low dosage. This article aims to highlight the progress and failures in the development of different types of traditional vaccines, along with the procedures and techniques used in traditional vaccine production.

As the volumetric modulated arc therapy (VMAT) becoming a main role of treatment ways, the effect of couch top becomes more significant. It is imperative to re-evaluate the couches that previously may have been considered of no importance during early treatment techniques. The impact of couch top on radiation delivery was explored and the couch model was tested with the aim of reducing the couch absorption influences.  Attenuation measurements were performed in a cylindrical phantom with an ionization chamber positioned at the isocenter. Couch model was obtained by importing its actual CT scan, and the accuracy was evaluated by comparing percentage deviation at 2 and 5 mm voxel grid size. Effects on surface dose were measured using EBT3 film with the constant SSD at different depths and beam energies at the gantry angle 180° and 0°, respectively. Couch top increases surface dose from 45.9 % to 95.8 % , from 35.0 % to 87.9 % and from 29.2% to 73.9 % for 10 cm ×10 cm field at 6 ,10 and 18 MV, respectively. Due to the couch absorption the case of vertebral metastasis VMAT plan D50 of the PTV changed from 30 Gy to 29.3 Gy. Couch model with uniform electron density of 0.18g/cm3 demonstrated an excellent agreement between measured and TPS computed dose. The treatment couch presence between the patient and beam source significantly alters dose in the patient. Modelling the couch in the Monaco TPS can adequately predict the altered dose distribution.

Objective (s): Recently, the use of nanoparticles in medicine has increased for radiation protection purpose. So the aim of this study was application of nano Bi2O3 in prepared shield for dose reduction during medical imaging. Nano Bi2O3 shield with 90% silicon and 10% nano Bi2O3 was prepared and dosimetry test was down in radiology by PTW DIADOS E dosimeter. The mean dose without using nano Bi2O3 shields were 421 µGy, 733 µGy and 1110 µGy for 60, 80 and 100 kVp , respectively. After using 0.5 mm thickness of nano Bi2O3 shield dose reduction in 60, 80 and 100 kVp was 42%, 35% and 31%. A comparison between increasing energy from 60 to 100 kVp and dose reduction showed a significant reverse effect. The results indicate that the new shields containing nano Bi2O3 particles have a high X-rays attenuation ability but the attenuation property of the shields was decreased by the increasing of the energy. Based on the results, this new shield can help social health and decline the radiation risk.

It has recently been shown that the particle size of materials used for radiation shielding can affect the magnitude of radiation attenuation. Over the past years, application of nano-structured materials in radiation shielding has attracted attention world-wide. The purpose of this study was to investigate the shielding properties of the lead-free shields containing micro and nano-sized WO3 against low energy x-rays.
The radiation shields were constructed using nano and micro WO3 particles incorporated into an EPVC polymer matrix. The attenuation coefficients of the designed shields were evaluated for low energy x-rays (diagnostic radiology energy range).
The results indicate that nano-structured WO3/PVC shields have higher photon attenuation properties compared to those of the micro-sized samples.
Our experiment clearly shows that the smaller size of nano-structured WO3 particles can guarantee a better radiation shielding property. However, it is too early to draw any conclusion on the possible mechanisms of enhanced attenuation of nano-sized WO3 particles.

The diagnostic accuracy of single photon emission computed tomography (SPECT) is profoundly influenced by attenuation phenomenon. Soft tissue attenuation degrades cardiac SPECT image quality, thereby decreasing the possibility of the detection of the lesions. A variety of correction techniques based on different assumptions have been used to reduce the impact of attenuation. Several types of systems with different transmission hardware modifications and external sources have been developed for clinical implementation. Each system has unique advantages and limitations. In this study, firstly, we introduce the attenuation phenomenon, the problems arising from it and the attenuation correction methods with description of the assumptions related to each of them. The main purpose of this study is to review the developments in the field involving various configurations used for attenuation correction of SPECT images, as tested using either phantom or clinical data, and to delineate an optimal attenuation correction technique by considering the advantages and limitations with each of the configurations.

Haemonchus contortus causes severe economic losses in small rumi­nants, so this study was conducted to study the UV effect on H. contortus larvae and its protective effect. Sixteen male goats were divided into 5 groups, control infected, con­trol uninfected and UV 30minutes exposure; UV 60minutes exposure and UV booster 60minutes exposure. The UV groups were exposed to UV irradiation at wave length 254 nm for 30 and 60 minutes. The UV booster 60min was adminis­trated 2 doses of exposed larvae with an interval of one month. All groups except the control negative one were challenged for 42 days from the beginning. In UV booster 60 min had reduction in egg count per gram feces and worm burden (93% & 34 % respectively). The establishment rate and relative fertility declined in comparison with other groups. These parameters were simi­lar in control infected, UV 30min and UV 60min groups. PCV value of UV booster 60min group was similar to uninfected group. After two weeks from the booster dose of irradiated larvae, increased levels of antibody were found in goats of UV booster 60min group. Two doses of UV 60min exposure, with an interval of one month, gave reduction not only in egg per gram feces but in worm burden as well.