Dual energy radiography using X-ray films and intensifying screens

The aim of this study was to investigate dual energy (DE) systems using X-ray films and intensifying screens as detecting media. This has been studied using both experimental methods and numerical modelling. Numerical methods were used to calculate energy losses due to K-fluourescent escape originating from the phosphors of the intensifying screens. This enabled the calculation of absorbed energy in screens. The method for screen selection and prediction of performance used the fact that detector response depends upon impinging X-ray energy. By equating the detector's absorbing characteristics to the resultant optical density (OD), an absorbed energy constant was calculated. These constants were used to predict OD for a given X-ray spectrum and hence simulation of detector characteristics. Experimental techniques were used to investigate sensitivity to chemical composition changes. These results compared favourably with computed values. It was demonstrated that although limitations exist, detector simulations are valid and X-ray film intensifying screen combinations make adequate DE detectors.     

Small-animal X-ray dose from micro-CT

The use of micro-CT in small animals has increased in recent years. Although the radiation levels used for micro-CT are generally not lethal to the animal, they are high enough where changes in the immune response and other biological pathways may alter the experimental outcomes. Therefore, it is important to understand what the doses are for a specific imaging procedure. Monte Carlo simulation was used to evaluate the radiation dose to small animals (5-40 mm in diameter) as a result of X-ray exposure. Both monoenergetic (6-100 keV) and polyenergetic (15-100 kVp) X-ray sources were simulated under typical mouse imaging geometries. X-ray spectral measurements were performed on a mouse imaging X-ray system using a commercially available X-ray spectrometer, and spectra from high-energy systems were used as well. For a typical X-ray system with 1.0 mm of added Al at 40 kVp, the dose coefficients (dose to mouse per air kerma at isocenter) were 0.80, 0.63, 0.52, and 0.44 mGy/mGy for mouse diameters of 10, 20, 30, and 40 mm, respectively. A number of tables and figures are provided for dose estimation over a range of mouse imaging geometries.     

Application of tomographic methods in the diagnosis of pathological changes of the jaw

The aim of this study was to evaluate the frequency of specific diagnostic methods used for diagnosis of oral pathologies. The sample consisted of 198 patients (98 man and 100 women) with formulated diagnosis, confirmed postoperatively by histopathological verification. In 74.7% of subjects only X-ray diagnostic examination was used. Both X-ray and computed tomography (CT) examinations were used in 18.7% of subjects. Magnetic resonance imaging (MRI) wasn't performed in any subject. In 6.6% of subjects neither X-ray nor CT was performed. The study reported on statistically significant differences in the distribution of specific diagnostic methods according to age groups (p = 0.026). Also, there was statistically significant differences in the distribution of diagnostic methods according to diagnostic groups (p = 0.053). In the group of 37 subjects, in whom both X-ray and computed tomography were used, the majority had carcinomas, followed by fractures and inflammatory cysts.     

Neutron imaging versus standard X-ray densitometry as method to measure tree-ring wood density

Neutron imaging is a new non-destructive testing method in wood science. It is similar to X-ray methods but with differing sensitivities for different elements. In this study, neutron imaging was used to ascertain the density profiles of thin spruce samples and compared with results generated with standard X-ray microdensitometry. Data obtained through neutron imaging were similar to those resulting from the X-ray method. The advantage of neutron imaging is its higher sensitivity to some elements such as hydrogen. Together with the high neutron-sensitivity of the applied detectors (imaging plates) this makes shorter exposure times possible, and yields more detailed information on the inner composition of wood. X-ray film, which is still most commonly used in X-ray densitometry, has the disadvantage that the relationship between the optical density of the film and the density of wood is non-linear. This means that corrections and calibration with step wedges are necessary, whereas with neutron imaging the digital values can be used directly to calculate the density at a certain point of the specimen. Thus neutron imaging appears to be an appropriate method, which can be used as complement to established X-ray methods for fast and straightforward investigations of tree rings, growth zones and wood density.     

Effects of Vitamins C and E Combination on Element Levels in Blood of Smoker and Nonsmoker Radiology X-Ray Technicians

X-ray radiation is detrimental to human cells and may lead to development of life-threatening diseases. Cigarette paper and cigarette smoke contain toxic elements, whereas vitamins C and E (VCE) may have regulator effects on the elements. We investigated effects of VCE administration on X-ray-induced element changes in blood of smoker and nonsmoker X-ray technicians. Twenty technicians and 30 healthy age-matched control subjects were used in the study. Ten of the X-ray technicians and 15 of the control were smokers. Blood serum samples were taken from the control. Oral vitamins C (500 mg) and E (150 mg) were supplemented daily to the smoker and nonsmoker X-ray technicians for 5 weeks. Serum samples were taken from the X-ray technicians before and after 5 weeks. Copper, zinc, selenium, aluminum, iron, magnesium, and calcium levels were investigated in control and X-ray technicians, both smokers and nonsmokers. Copper, zinc, and selenium levels were lower in the total X-ray group and smoker X-ray group than in control and nonsmoker X-ray group, although iron, magnesium, and calcium levels were higher in X-ray group than in control. The copper, zinc, selenium, and aluminum levels were higher in the VCE treatment group than those in X-ray group, although magnesium and calcium levels were decreased by the treatment. The serum zinc, copper, selenium, and magnesium levels were lower in smoker control group when compared to nonsmoker control group. The serum zinc levels were lower in smoker X-ray group than nonsmoker X-ray group, although iron level was higher in smoker X-ray group than in nonsmoker X-ray group. VCE prevents the smoke and X-ray-induced selenium, zinc, magnesium, and copper decrease to strengthen the antioxidant trace element levels in the serum of the technicians.     

Structure of porcine heart cytoplasmic malate dehydrogenase: combining X-ray diffraction and chemical sequence data in structural studies

The amino acid sequence of cytoplasmic malate dehydrogenase (sMDH) has been determined by a combination of X-ray crystallographic and chemical sequencing methods. The initial molecular model incorporated an "X-ray amino acid sequence" that was derived primarily from an evaluation of a multiple isomorphous replacement phased electron density map calculated at 2.5-A resolution. Following restrained least-squares crystallographic refinement, difference electron density maps were calculated from model phases, and attempts were made to upgrade the X-ray amino acid sequence. The method used to find the positions of peptides in the X-ray structure was similar to those used for studying protein homology and was shown to be successful for large fragments. For sMDH, X-ray methods by themselves were insufficient to derive a complete amino acid sequence, even with partial chemical sequence data. However, for this relatively large molecule at medium resolution, the electron density maps were of considerable help in determining the linear position of peptide fragments. The N-acetylated polypeptide chain of sMDH has 331 amino acids and has been crystallographically refined to an R factor of 19% for 2.5-A resolution diffraction data.     

Applications of neutron and X-ray scattering to the study of biologically relevant model membranes

Scattering techniques, in particular electron, neutron and X-ray scattering have played a major role in elucidating the static and dynamic structure of biologically relevant membranes. Importantly, neutron and X-ray scattering have evolved to address new sample preparations that better mimic biological membranes. In this review, we will report on some of the latest model membrane results, and the neutron and X-ray techniques that were used to obtain them.     

Distribution and orientation of the collagen fibers in the tunica media of muscular arteries

X-ray diffraction tecniques were used to study the distribution and orientation of collagen fibers in media layer of human muscular arteries as a function of mechanical deformation. The close relationship between collagen fibers and smooth cells orientation was shown by X-ray diffraction and histological analyses.     

Detection and determination of selenoproteins by nuclear techniques

Microbeam X-ray spectrometry, energy-dispersive X-ray fluorescence analysis, and neutron activation analysis were evaluated for the detection of selenium contained in the selenoprotein glutathione peroxidase. The glutathione peroxidase had been previously separated using polyacrylamide gel electrophoresis. The use of Bragg-reflected polarized X-ray beams was employed in the X-ray fluorescence measurements to minimize the problem of scatter owing to the gel matrix. Current detection limits of selenium in a gel matrix are 2.1 ng in the bench-top microbeam X-ray system and 30–60 ng using XRF with polarized beams. Neutron activation analysis was used for qualitycontrol measurements, with a detection limit here of <0.08 ng. The work has in principle established the feasibility of such an approach.     

Crystallinity and structure of starch using wide angle X-ray scattering

Wide angle X-ray diffraction was used to evaluate the crystalline fraction of a variety of starches, using preliminary smoothing then an iterative smoothing algorithm to estimate amorphous background scattering. This methodology was then used to determine initial crystallinity and monitor gelation and retrogradation of high amylose thermoplastic starch used to produce film. Retrogradation was monitored over a 5-day period. It was found that the starch film retrograded rapidly over the first 12 h with the film displaying both B-type crystallinity and long range amorphous ordering that were separately quantitatively calculated. Changes in starch films, including complete or partial gelatinization, retrogradation and crystallinity, were all determined through wide angle X-ray diffraction.     

Outer membrane proteins: comparing X-ray and NMR structures by MD simulations in lipid bilayers

The structures of three bacterial outer membrane proteins (OmpA, OmpX and PagP) have been determined by both X-ray diffraction and NMR. We have used multiple (7 × 15 ns) MD simulations to compare the conformational dynamics resulting from the X-ray versus the NMR structures, each protein being simulated in a lipid (DMPC) bilayer. Conformational drift was assessed via calculation of the root mean square deviation as a function of time. On this basis the ‘quality’ of the starting structure seems mainly to influence the simulation stability of the transmembrane β-barrel domain. Root mean square fluctuations were used to compare simulation mobility as a function of residue number. The resultant residue mobility profiles were qualitatively similar for the corresponding X-ray and NMR structure-based simulations. However, all three proteins were generally more mobile in the NMR-based than in the X-ray simulations. Principal components analysis was used to identify the dominant motions within each simulation. The first two eigenvectors (which account for >50% of the protein motion) reveal that such motions are concentrated in the extracellular loops and, in the case of PagP, in the N-terminal α-helix. Residue profiles of the magnitude of motions corresponding to the first two eigenvectors are similar for the corresponding X-ray and NMR simulations, but the directions of these motions correlate poorly reflecting incomplete sampling on a ∼10 ns timescale.     

Preparation, chemical and crystal structures of N-(2-acetamido-3,4,6-tri-O-acetyl-2-deoxy-beta-D-glucopyranosyl)pyridinium chloride

Preparation and isolation of N-(2-acetamido-3,4,6-tri-O-acetyl-2-deoxy-beta-D-glucopyranosyl)pyridinium chloride are described. Its structure was determined by 1H NMR spectroscopy and X-ray analysis. X-ray crystallography revealed that the salt crystallizes with one molecule of water. Ab initio calculations were used to determine charges on atoms in the cation of the title compound.     

X-ray densitometry of the axial skeleton and ultrasound densitometry of the calcaneus: potentialities and values of the techniques in clinical practice

Double-power X-ray absorptiometry of the axial skeleton and ultrasound densitometry of the calcaneus were used to examine 3 groups of patients: 58 with chronic renal failure (CRF), 73 with senile osteoporosis, and 78 with diabetes mellitus (DM). The examination has indicated that X-ray absorptiometry is the most informative method in diagnosing osteoporosis in patients with CRF and DM. Ultrasound densitometry is of informative value only in patients with senile osteoporosis and it may be used as a screening tool in this category of patients.     

Trace metal levels of X-ray technicians' blood and hair

Medical X-ray technicians are exposed to low-level ionizing radiation in their occupational field. There are very few data on low-dose radiation effects. The present study was designed to estimate a few vital trace metals (Zn, Cu, Fe) in indicator tissues (blood and hair) of X-ray technicians and non-X-ray technicians (hospital employees were used as controls) by Atomic Absorption Spectrometry (AAS). This analysis noted a significant increase in Zn, Cu, and Fe concentrations in X-ray technicians' hair. But in blood, Zn and Cu were depleted, whereas Fe was increased. Such changes in trace metal concentrations among X-ray technicians were noted where occupational exposure to radiation was for longer than three years. Through composite risk analysis, by using Zn:Fe as an indicator, it was noted that blood gave a stronger indication than hair in analyzing and estimating risk.     

The nature of radiation-induced mutations at the white locus of Drosophila melanogaster

X-Ray- and neutron-induced mutations at the white locus of Drosophila melanogaster were used to study the nature of radiation-induced genetic damage. Genetic analysis showed the presence of multi-locus deficiencies in 15 out of 31 X-ray mutants and in 26 out of 35 mutants induced by neutrons. The DNA from 11 X-ray and 4 neutron mutants, which were not multi-locus deficiencies, was analyzed by Southern blot-hybridization. Deletions were observed in 2 X-ray and 1 neutron mutant. In combination with cytogenetic techniques, chromosomal rearrangements affecting the white locus (translocations, inversions, etc.) were identified in 3 X-ray and in 2 neutron mutants. A hot-spot for translocation breakpoints was identified in the left arm of the third chromosome. 5 X-ray mutants, which apparently did not contain large deletions, were subjected to further analysis by the nuclease S1 protection method, after cloning of the white gene. In 4 mutants a small deletion could indeed be detected in this way. Thus it seems that by far the main part of X-ray- and neutron-induced white mutants have arisen through large changes in the white gene, especially deletions.     

Ageing Cattle: The Use of Radiographic Examinations on Cattle Metapodials from Eketorp Ringfort on the Island of ?land in Sweden

In this paper conventional X-ray analysis of cattle metapodials is used to study the age structure of slaughtered cattle at Eketorp ringfort on the island of Öland, Sweden. The X-ray analyses suggest that several animals in both phases were slaughtered aged 4–8 years. More oxen/bulls than cows reached the advanced age of over 8 years, yet in phase III more oxen/bulls seem to have been slaughtered between the ages of 2 and 8 years. These differences may reflect a change in demand for meat related to the character of the site. The results also show a correlation between metapodials with a pathology connected to biomechanical stress and older animals. This suggests that male cattle were used both in meat production and as draught animals. Asymmetry in male metatarsals such as distal broadening of the lateral part of the medial trochlea was visible on the X-ray images. The bone element also indicates a denser outer cortex of the medial diaphysis in comparison to the inner medulla. This could be the result of repetitive mechanical stress. Two metatarsals from cows were documented with distal asymmetry indicating that cows were also used as working animals. Bone elements with changes in the articular surfaces were more common in metapodials from cows with an X-ray age of over 3–4 years. These results highlighted the slaughter age difference between oxen/bulls and cows, enabling a better understanding of animal husbandry and the selection of draught cattle at Eketorp ringfort.     

Ghrelin在正常及X线辐射损伤小鼠睾丸中的表达

目的探讨ghrelin在正常及X射线辐射损伤后小鼠睾丸中的表达变化及其意义。方法采用辐射剂量1·0GyX线对成年小鼠进行全身照射,于照射后16h取睾丸组织制备标本,免疫组织化学ABC法检测ghrelin在辐射损伤小鼠及正常对照组小鼠睾丸中的表达,探讨ghrelin表达的变化及意义。结果正常小鼠睾丸ghrelin主要表达在间质细胞的胞浆中,呈强阳性。X线照射后16h,ghrelin的表达主要集中于生精小管内各级生殖细胞中,特别是在精原细胞和初级精母细胞中有强阳性反应,且其表达具有生精周期特异性,而间质细胞中呈阴性。结论Ghrelin在小鼠正常及辐射损伤睾丸中的特异性表达和变化,提示其可能与睾丸精子发生、精子形成及辐射损伤修复有关,具有重要的睾丸生物学调节功能。     

Microfocal X-ray CT imaging and pulmonary arterial distensibility in excised rat lungs

The objective of this study was to develop an X-ray computed tomographic method for measuring pulmonary arterial dimensions and locations within the intact rat lung. Lungs were removed from rats and their pulmonary arterial trees were filled with perfluorooctyl bromide to enhance X-ray absorbance. The lungs were rotated within the cone of the X-ray beam projected from a microfocal X-ray source onto an image intensifier, and 360 images were obtained at 1 degrees increments. The three-dimensional image volumes were reconstructed with isotropic resolution using a cone beam reconstruction algorithm. The vessel diameters were obtained by fitting a functional form to the image of the vessel circular cross section. The functional form was chosen to take into account the point spread function of the image acquisition and reconstruction system. The diameter measurements obtained over a range of vascular pressures were used to characterize the distensibility of the rat pulmonary arteries. The distensibility coefficient alpha [defined by D(P) = D(0)(1 + alphaP), where D(P) is the diameter at intravascular pressure (P)] was approximately 2.8% mmHg and independent of vessel diameter in the diameter range (about 100 to 2,000 mm) studied.     

Estimation of uncertainties in X-ray refinement results by use of perturbed structures

The uncertainties in the refined parameters for a 1.5-A X-ray structure of carbon-monoxy (FeII) myoglobin are estimated by combining energy minimization with least-squares refinement against the X-ray data. The energy minimizations, done without reference to the X-ray data, provide perturbed structures which are used to restart conventional X-ray refinement. The resulting refined structures have the same, or better, R-factor and stereochemical parameters as the original X-ray structure, but deviate from it by 0.13 A rms for the backbone atoms and 0.31 A rms for the sidechain atoms. Atoms interacting with a disordered sidechain, Arg 45 CD3, are observed to have larger positional uncertainties. The uncertainty in the B-factors, within the isotropic harmonic motion approximation, is estimated to be 15%. The resulting X-ray structures are more consistent with the energy parameters used in simulations.