In situ study on columnar-equiaxed transition and anaxial columnar dendrite growth of Al-15%Cu alloy by synchrotron radiography

Directional solidification of Al-15% （mass fraction） Cu alloy was investigated by in situ and real time radiography which was performed by Shanghai synchrotron radiation facility （SSRF）. The imaging results reveal that columnar to equiaxed transition （CET） is provoked by external thermal disturbance. The detaching and floating of fragments of dendrite arms are the prelude of the transition when the solute boundary layer in front of the solid-liquid interface is thin. And the dendrite triangular tip is the fracture sensitive zone. When the conditions are suitable, new dendrites can sprout and grow up. This kind of dendrite has no obvious stem and is named anaxial columnar dendrites.

Resolution analysis of thermal neutron radiography based on accelerator-driven compact neutron source

Owing to the immobility of traditional reactors and spallation neutron sources,the demand for compact thermal neutron radiography(CTNR)based on accelerator neutron sources has rapidly increased in industrial applications.Recently,thermal neutron radiography experiments based on a D-T neutron generator performed by Hefei Institutes of Physical Science indicated a significant resolution deviation between the experimental results and the values calculated using the traditional resolution model.The experimental result was up to 23%lower than the calculated result,which hinders the achievement of the design goal of a compact neutron radiography system.A GEANT4 Monte Carlo code was developed to simulate the CTNR process,aiming to identify the key factors leading to resolution deviation.The effects of a low collimation ratio and high-energy neutrons were analyzed based on the neutron beam environment of the CTNR system.The results showed that the deviation was primarily caused by geometric distortion at low collimation ratios and radiation noise induced by highenergy neutrons.Additionally,the theoretical model was modified by considering the imaging position and radiation noise factors.The modified theoretical model was in good agreement with the experimental results,and the maximum deviation was reduced to 4.22%.This can be useful for the high-precision design of CTNR systems.

Imaging internal density structure of the Laoheishan volcanic cone with cosmic ray muon radiography

Muon radiography is a promising technique for imaging the internal density structures of targets such as tunnels,pyramids,and volcanoes up to a scale of a few hundred meters by measuring the flux attenuation of cosmic ray muons after they have traveled through these targets.In this study,we conducted experimental muon radiography of one of the volcanoes in the Wudalianchi area in Northeast China to image its internal density structure.The muon detector used in this study was composed of plastic scintillators and silicon photomultipliers.After approximately one and a half months of observing the crater and conduit of the Laoheishan volcano cone in Wudalianchi from September 23^(rd) to November 10^(th) 2019,more than 3 million muon tracks fulfilling the data selection criteria were collected.Based on the muon samples and high-resolution topography obtained through aerial photogrammetry using an unmanned aerial vehicle,a density image of the Laoheishan volcano cone was constructed.The results obtained in this experiment demonstrate the feasibility of using a radiography technique based on plastic scintillator detectors.To obtain the density distribution,we performed a detailed background analysis and found that low-energy charged particles dominated the background noise.Relatively higher densities were found near the surface of the volcanic cone,whereas relatively lower densities were found near the center of the volcanic cone.The experiment in this study is the first volcano muon tomography study performed in China.Our work provides an important reference for future research.

Monte Carlo simulation for bremsstrahlung and photoneutron yields in high-energy x-ray radiography

This paper reports on the results of calculations using a Monte Carlo code （MCNP5） to study the properties of photons, electrons and photoneutrons obtained in the converted target and their transportations in x-ray radiography. A comparison between measurements and calculations for bremsstrahlung and photoneutrons is presented. The radiographic rule and the effect of the collimator on the image are studied with the experimental model. The results provide exact parameters for the optimal design of radiographic layout and shielding systems.

Areal density and spatial resolution of high energy electron radiography

Ultrafast imaging tools are of great importance for determining the dynamic density distribution in high energy density(HED)matter.In this work,we designed a high energy electron radiography(HEER)system based on a linear electron accelerator to evaluate its capability for imaging HED matter.40 MeV electron beams were used to image an aluminum target to study the density resolution and spatial resolution of HEER.The results demonstrate a spatial resolution of tens of micrometers.The interaction of the beams with the target and the beam transport of the transmitted electrons are further simulated with EGS5 and PARMELA codes,with the results showing good agreement with the experimental resolution.Furthermore,the experiment can be improved by adding an aperture at the Fourier plane.

Proton radiography of magnetic fields generated with an open-ended coil driven by high power laser pulses

Recently generation of strong magnetic(B)fields has been demonstrated in capacitor coils heated by high power laser pulses[S.Fujioka et al.,Sci.Rep.3,1170(2013)].This paper will present a direct measurement of B field generated with an open-ended coil target driven by a nanosecond laser pulse using ultrafast proton radiography.The radiographs are analyzed with particle-tracing simulations.The B field at the coil center is inferred to be ~50 T at an irradiance of ~5×10^(14) W·cm^(-2).The B field generation is attributed to the background cold electron flow pointing to the laser focal spot,where a target potential is induced due to the escape of energetic electrons.

Noise analysis of grating-based x-ray differential phase-contrast imaging with angular signal radiography

X-ray phase-contrast imaging is one of the novel techniques,and has potential to enhance image quality and provide the details of inner structures nondestructively.In this work,we investigate quantitatively signal-to-noise ratio（SNR） of grating-based x-ray phase contrast imaging（GBPCI） system by employing angular signal radiography（ASR）.Moreover,photon statistics and mechanical error that is a major source of noise are investigated in detail.Results show the dependence of SNR on the system parameters and the effects on the extracted absorption,refraction and scattering images.Our conclusions can be used to optimize the system design for upcoming practical applications in the areas such as material science and biomedical imaging.

A Derived Exposure Chart for Computed Radiography in a Negroid Population

Background: Computed radiography has a wider exposure latitude when compared with film-screen imaging system. Consequently, the risk of dose creep is high. A conscientious effort is there-fore, needed by the radiographer to keep exposure as low as reasonably achievable. Objective: To derive a computed radiography exposure chart for a negroid population using AGFA photostimulable phosphor plates and a GE static X-ray machine. Materials and Method: A static X-ray machine, a digitizer, and photostimulable phosphor plates were used for the X-ray examination. Chest examinations were done at a Focus-Film-Distance (FFD) of 150 - 180 cm while all other examinations were conducted at 90 - 100 cm FFD. The range of exposure factors (kVp, mA and mAs) used by radiog-raphers in the centre was noted and the 90th percentile calculated. Over a three-month period, the patients were examined with the 90th percentile of tube potential (kVp) while keeping other factors constant. The kVp was gradually decreased and halted if radiologists and radiographers uncon-nected with the work expressed misgivings about the quality of the image. A similar procedure was adopted for the tube current (mA). The threshold adopted as low as reasonably achievable was the factor preceding the point of observation by other personnel. Metrics for central tendency from the statistical packages for social sciences, version 17.0 was used to analyze the data. Results: 335 subjects of both gender aged 0 - 92 years were examined by the researchers. Adult exposure factors used by the radiographers (and those derived by the researchers) had a range of 45 - 130 kVp (62 - 94 kVp), 63 - 320 mA (100 - 250 mA) and 4.0 - 25.0 mAs (5.0 - 20.0 mAs) respectively. Pediatric chest (and researchers-derived) factors were 50 - 75 kVp (52 - 65 kVp), 50 - 250 mA (100 - 220 mA) and 3.20 - 10.0 mAs (3.2 - 6.5 mAs) respectively. Conclusion: Upper threshold of adult (and paediatric) exposure factors in computed radiography with comparable equipment and accessories should not exceed 94 kVp (65 kVp), 250 mA (220 mA) and 20.0 mAs (6.5 mAs) respectively. The derived exposure chart is also adequate to address motion unsharpness in chest examinations.

Signal-to-noise ratio comparison of angular signal radiography and phase stepping method

Grating-based x-ray phase contrast imaging has the potential to be applied in future medical applications as it is compatible with both laboratory and synchrotron source. However, information retrieval methods are important because acquisition speed, scanning mode, image quality, and radiation dose depend on them. Phase-stepping （PS） is a widely used method to retrieve information, while angular signal radiography （ASR） is a newly established method. In this manuscript, signal-to-noise ratios （SNRs） of ASR are compared with that of PS. Numerical experiments are performed to validate theoretical results. SNRs comparison shows that for refraction and scattering images ASR has higher SNR than PS method, while for absorption image both methods have same SNR. Therefore, our conclusions would have guideline in future preclinical and clinical applications.

Mega-Electron-Volt Electron Scattering and Radiography of Plasma

A Monte Carlo code is developed to study mega-electron-volt （MeV） electron scattering and transport in plasma based on multiple scattering. A scaling law relating the angular width of a scattered beam to the incident electron energy and the areal density of plasma is found, which may provide a method of MeV electron radiography for diagnosing the area/density of high-temperature, dense plasma under fusion conditions. The study on the MeV electron beam radiography also shows that plasma density interfaces could be discriminated by electron scattering.

Comparison via Digital Radiography of Radiopacity Levels of Composite Materials with Various Shades and Viscosities

Aim of the present in vitro study is to evaluate the radiopacity levels of composite resins with various shades and viscosity.10 mm×2 mm discs were prepared from 7 condensable and 4 flowable composites(n=10).An aluminum step wedge ranging from 2.0 to 10.0 mm in thickness was placed on the occlusal film.Digital radiographs were taken using a dental X-ray device and radiographic densities of each step of the aluminum wedge and the samples were recorded to the computer.Five readings were taken and means were calculated.One-Way Anova and Tamhane post hoc tests were performed.While G-eanial Posterior has the highest radiopacity value followed by Filtek Z550,Aelite Flo has the lowest radiopacity value.Posterior composites show higher radiopacity and flowable composites with higher filler loadings have superior radiopacity levels to condensable composites.Enamel and body shades of the composite brands have also statistically significant differences in radiopacity scores.Eventually,radiopacity level of a composite resin material is not affected by the size of fillers;however,the composition,shape and loading of the fillers can specify the radiodensity.

Thin-film approximate point scattered function and its application to neutron radiography

A simpler and improved utility approximate point scattered function for thin-film converters currently used in neutron photographic devices is proposed as a correction method to produce clearer,more realistic images.The validity of the model was demonstrated through a simulation experiment.Based on the results,an error analysis was carried out,certain corrections were made to the original model,and the final model achieved a very low relative error in the simulation experiment.The model can also be optimized for quantitative neutron photographic analysis using iterative algorithms to obtain realistic neutron photographic images more quickly.At the end of the article,the model is extended to consider the case of energy spectrum hardening by introducing a temperature correction parameter.

Does shifting to professional emergency department staffing affect the decision for chest radiography?

BACKGROUND: The study aims to determine whether shifting to professional emergency department(ED) teams leads to a higher rate of radiologic workup.METHODS: We retrospectively analyzed a total of 2,000 patients presenting to the ED of a tertiary teaching hospital in two time periods: group 1(G1) comprised 1,000 consecutive patients enrolled from December 21, 2012 to January 5, 2013(all patients were examined by an internal medicine specialist);group 2(G2) comprised 1,000 consecutive patients enrolled from December 21, 2018 to January 3, 2019(all patients were examined by an emergency physician).RESULTS: The chest X-ray(CXR) was performed in 40.6% of all patients. There was no difference in the frequency of CXR(38.9% in G1 vs. 42.3% in G2, P=0.152). More CXRs were performed in G2 patients older than 65 years, in female patients older than 65 years, in patients presenting during the evening and night shifts or off-hours, in patients with a history of malignancy, in patients with gastrointestinal bleeding, and in patients with bradycardia, but fewer in patients presenting with arrhythmia. No difference in the rates of pathological CXR was found(47.3% in G1 vs. 52.2% in G2, P=0.186). Compared with G2, higher sensitivity and specificity were obtained for the binary logistic regression model predicting pathological findings in G1.CONCLUSIONS: Shifting to professional ED teams does not increase radiologic workup. By implementing deliberate usage of ultrasound, some self-governing procedures, case-oriented investigations, and center-specific recommendations, unnecessary radiologic workup can be avoided. Professional ED teams could lead to a higher standard of emergency care.

Development of Brief Image Quality Evaluation Criteria for Digital OrthoPantomography （OPG） Images in Dental Radiography

An OPG （orthopantmography） is an extra-oral radiographic imaging method which provides a panoramic or wide view of both jaws and teeth on a single image. Digital OPG images provide high contrast with more details of the dentitions. The research main objective was to produce sophisticated and effective criteria that can be used by any radiographer with sound knowledge to identify common errors of digital OPG images and to increase the concern of high frequency of errors to minimize them to give an optimum image quality. The study was designed as retrospective cross sectional study. Hundred digital OPG images are evaluated by three qualified radiographers who had dental radiography experience and four student radiographers. Paired t-test was used to see the difference between the responses of radiographers and student radiographers. Kruskal-Wallis Test was used to see difference between each evaluator. Possible errors of OPG were divided into four main categories （identification, artifact, anatomical coverage and patient positioning）. Each main category consists of sub-categories. Values of subcategories were given according to their importance to get the total of 100% for each main category. The results showed that there is no significant difference between radiographers and student radiographers’ responses and also between each evaluator. Hence it shows that the criteria were an easy understandable and user-friendly tool. And results showed the frequent error category was loss of anatomical coverage and frequent error was absence of positioning the tongue against the palate.

General Radiography as Clue for the Working Diagnosis: Sacrospinous Ligament Calcification Leading to Left Ureteric Calculus with Non-Functioning Kidney

General radiography leaves enough clues for the ongoing diagnostic evaluation of the patient. The important clues can save a lot of time lost and other unnecessary investigations in the management of the patient illness. Sacrospinous ligament connects the sacrum with the pelvis. This in fact stabilizes the pelvis as it provides the support. This is important as this is helpful in supporting the vaginal vault in cases of prolapsed uterus in females. We report a 50-year-old male who had come for his intravenous pyelography for left ureteric calculus and was found to be having multiple other associated findings like osteophytosis, bilateral ilial horns and bilateral sacrospinous ligament calcifications. The clue was that of calcification and hardening of left sacrospinous ligament which has led to the formation of left side ureteric calculus. This ureteric calculus has caused great progressive damage to the left kidney by causing gross hydrouretero-nephrosis due to complete obstruction.

The review and prospect of neutron radiography in China

Neutron radiography is one of radiography non-destructive testing.It is a valuable complementary of X and γ rays radiography.The present status and history of neutron radiography in China was described briefly,facilities of neutron radiography and their development were introduced in this paper.

Specimen Radiography for MRI-Guided Biopsies

Background: Specimen radiography is important for the biopsy of breast microcalcifications, and MRI is limited in the detection of microcalcifications. It is unknown whether or not the presence of microcalcifications on MRI-guided biopsies is significant. Purpose: To determine whether specimen radiography of MRI-guided biopsy samples provides any added benefits in tissue assessment. Materials and Methods: This is an IRB-approved, HIPPA-compliant retrospective review of MRI-guided biopsy reports whose tissue underwent specimen radiography from 2010 to 2017. Pathology reports were queried to compare samples with and without calcium and reviewed to determine if calcifications correlated with the lesion of interest. If there was a correlation, the original MRI was reviewed. Final pathology reports were also reviewed if excision was performed. Results: A total of 889 patients ages 22 - 85 were included with 140 (15.7%, 140/889) containing calcifications. Of 140 specimens, 119 (85.0%, 119/140) cases separated the calcifications. A total of 41 (34.5%, 41/119) were malignant or high-risk lesions/atypia of which 15 (36.6%, 15/41) showed a higher-grade lesion in the specimen containing calcium. Out of these 15, 4 (26.7%, 4/15) were pathologically associated with calcium;however, pathologic diagnosis was not dependent on the presence of calcifications. All 4 were high-risk lesions and none were malignancies. MRI in these cases showed three enhancing masses and one non-mass enhancement. None were upgraded at excision. Conclusion: The presence of microcalcifications on MRI-guided biopsies does not aid in tissue assessment and does not impact pathologic diagnosis. Specimen radiography provides no added benefits in the setting of MRI-guided biopsies.

图像融合技术在Computed Radiography影像中的应用研究

将图像融合技术应用于CR(ComputedRadiography)技术中 ,有效改善影像的信噪比 (signal-to -noiseratio)。运用双IP(ImagePlate)技术采集人体体模影像后 ,在变换域进行图像配准。建立融合图像的数学模型 ,基于此模型对配准完成的源图像实施不同权重的加权计算得到融合图像。结果 融合图像信噪比源图像可提高 30 %左右。结论 将图像融合技术应用于CR技术可有效改善影像质量 ,有助于提高诊断的准确性。

Evaluation of an asymptomatic COVID-19 patient post-surgery with chest radiography: A surgeon’s dilemma

Routine chest radiography is not a requirement in post-surgery cardiac bypass patients.However,the safety of abandoning routine chest radiographs in critically ill patients remains uncertain.Surgery in an asymptomatic coronavirus disease 2019(COVID-19)patient presents additional challenges in postoperative management.Chest radiography remains a valuable tool for assessment of all patients,even a stable one.Management of surgical patients as an emergency in an asymptomatic COVID-19 case remains a surgeon’s dilemma.

The Use of Esophageal Radiography in the Location of Atrial-Septal Puncture: Clinical Analysis of 486 Cases

Objectives To determine the safety and value of esophageal radiography as a means of locating transseptal puncture. Methods 486 patients who underwent transseptal puncture were randomized into two groups. An esophagus radiographic method of locating tansseptal puncture site was applied in the study group （n = 243 ） and modified-Ross locating method was used in the control group （n = 243 ）. After successful location, transseptal puncture was made. We observed the success rate and incidence complications in the 2 groups. Results Left atrium impression in the study group was clearly seen. Nonetheless in 120 cases of control group, the left atria silhouette was not clearly visualised. The success rate of locating transseptal puncture site in the study group and control group were 100% and 50. 6% respectively （ P 〈 0. 001 ）. The success rate of transseptal puncture in the study group and control group was 99. 6% and 45.7% respectively （ P 〈 0. 001 ）. There were no complications associated with puncture in the study group and pericardial tamponade occurred in 1 control patient. Conclusions The esophagus radiographic method of locating transseptal puncture site is accurate, safe and simple to perform. Transseptal puncture has a high success rate with few complications.