Research on the Influence of X-ray Phase Contrast Imaging Parameters with Micro-focus Source

X-ray in-line phase contrast imaging enables weakly to absorb specimens to be imaged successfully with high resolution and definition. In this paper we use computer simulation method to analyze how each parameter influences the quality of the image. It can avoid wasting unnecessary time and materials in the course of experiment to get ideal images.

Improvements to conventional X-ray tube-based cone-beam computed tomography system

Conventional X-ray tube-based cone-beam computed tomography(CX-CBCT) systems have great potential in industrial applications. Such systems can rapidly obtain a three-dimensional(3D) image of an object.Conventional X-ray tubes fulfill the requirements for industrial applications, because of their high tube voltage and power. Continuous improvements have been made to CX-CBCT systems, such as imaging time shortening,acquisition strategy optimization, and imaging software development, etc. In this study, a CX-CBCT system is developed. Additionally, some improvements to the CX-CBCT system are proposed based on the hardware conditions of the X-ray tube and detector. A near-detector(ND)geometry condition is employed to obtain a sharper image and larger detection area. An improved acquisition strategy is proposed to simplify operations and reduce total imaging time. In the ND geometry condition, a simplified method called FBP slice stacking(SS-FBP) is proposed, which can be applied to 3D image reconstruction. SS-FBP is timesaving relative to traditional methods. Furthermore, imaging software for the CX-CBCT system is developed in the MATLAB environment. Several imaging experiments were performed. The results suggest that the CX-CBCT system works properly, and that the above improvements are feasible and practical.

Experimental research on the feature of an x-ray Talbot–Lau interferometer versus tube accelerating voltage

X-ray Talbot-Lau interferometer has been used most widely to perform x-ray phase-contrast imaging with a con- ventional low-brilliance x-ray source, and it yields high-sensitivity phase and dark-field images of samples producing low absorption contrast, thus beating tremendous potential for future clinical diagnosis. In this work, by changing the accel- erating voltage of the x-ray tube from 35 kV to 45 kV, x-ray phase-contrast imaging of a test sample is performed at each integer value of the accelerating voltage to investigate the characteristic of an x-ray Talbot-Lau interferometer （located in the Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, Japan） versus tube voltage. Ex- perimental results and data analysis show that within a range this x-ray Talbot-Lau interferometer is not sensitive to the accelerating voltage of the tube with a constant fringe visibility of ~ 44%. This x-ray Talbot-Lau interferometer research demonstrates the feasibility of a new dual energy phase-contrast x-ray imaging strategy and the possibility to collect a refraction spectrum.

Effects of Tube Voltage on Phase-Contrast Imaging for Different Microfocus X-Ray Tubes

In the past decade, phase-contrast imaging (PCI) has become a hot research with an increased improvement of the image contrast with respect to conventional absorption radiography. In this paper, effects of tube voltage (kVp) on propagation-based phase-contrast imaging have been investigated with two types of microfocus x-ray tubes, a conventional sealed x-ray tube with the focal spot size of 13 - 20 μm and an open x-ray tube with minimum focal spot size less than 2 μm. A cooled x-ray CCD detector with the pixel size of 24 μm was used to acquire digital images. Two thin plastic sheets with different thickness were used as radiography phantoms. Two different phenomena were observed for the two x-ray tubes. For the open tube, phase-contrast effect has a slight drop with the increasing of tube voltage, however, it is opposite for the sealed tube. A further investigation indicates that the variation of focal spot size causes the abnormal result for the sealed tube. It also shows that phase-contrast effect is more sensitive to focal spot size than tube voltage.

Simulating Medical Imaging X-Ray Tubes with Various Parameters Using BEAMnrc Monte Carlo Software

Context: Medical imaging has a wide range of applications in today’s society. Basic projectional radiography, CT scans, mammograms and a range of other advanced technologies all use x-rays to create a large number of examinations every day across the world. The most essential component of such medical equipment is the x-ray tube, which creates and produces x-rays. Objective: We describe and investigate an abstract model-geometry of a simple x-ray tube utilizing the open-source software package of BEAMnrc of the EGSnrcmp family, which is well validated by several studies over the years, for high and low energy photons generation. Methodology: Our research focuses on two different electron beam energies: 120 keV and 30 keV. The 120 keV is the typical energy for simple projectional radiographic exams and CT examinations, whereas the 30 keV is the typical energy of mammography. Results: Two different anode materials are used for each case, Gold (Au) and Tungsten (W) for 120 keV because these are the most common in projectional radiography and CT;Molybdenum (Mo) and Rhodium (Rh) for 30 keV because with these targets most mammography exams are carried out. The aim of this work is to show how the BEAMnrc software package can simulate effectively x-ray generation of low-energy photons which are utilized in modern medical imaging procedures. We describe useful information on anode-target characteristics, such as anode angle, anode material, and metal filter materials, based on previous quality studies even by using software other than BEAMnrc. Conclusion: We demonstrate that BEAMnrc can be efficiently used for Monte Carlo modeling of low-energy photons.

Chemical Analysis of Hydroxyapatite Artificial Bone Powders by Energy Dispersive X-Ray Fluorescence Spectrometry(EDXRF)

Stoichiometric hydroxyapatite(HA)nanoparticles were synthesized by a wet chemical method.Calcium nitrate tetra hydrate used as calcium source and dibasic ammonium phosphate used as phosphorous source.Calcium nitrate tetra hydrate and dibasic ammonium phosphate solutions were prepared by dissolving the salts in distilled water.Stoichiometric hydroxyapatite nanoparticles used by artificial bone powders and synthesized by a wet chemical method were analyzed using EDXRF method.The concentrations of K,Ca,Ti,V,Cr,Fe,Ni,Cu,Sr and Pb for artificial bone powders have been determined.Besides,Calcium contents were evaluated according to the agitation time and temperature in the production process.

Naso-jejunal tube insertion-interface between radiology and endoscopy

A survey was performed to identify the practice associated with endoscopic placement of naso-jejunal(NJ) tubes. We had a total of 236 responses, of which 228 responded to the frequency of requesting X-rayafter placing NJ tubes. The responses suggested that there was a strong variation in the practice. The practice was independent on clinicians' area of interest, hospital setting or experience in endoscopy. Currently there are no accepted guidelines on this. Hence, we advise hospitals to have robust local guidelines until there is internationally agreed consensus.

Energy spectrum of multi-radiation of X-rays in a low energy Mather-type plasma focus device

The multi-radiation of X-rays was investigated with special attention to their energy spectrum in a Mather-type plasma focus device （operated with argon gas）. The analysis is based on the effect of anomalous resistances. To study the energy spectrum, a four-channel diode X-ray spectrometer was used along with a special set of filters. The filters were suitable for detection of medium range X-rays as well as hard X-rays with energy exceeding 30 keV. The results indicate that the anomalous resistivity effect during the post pinch phase may cause multi-radiation of X-rays with a total duration of 300 ± 50 ns. The significant contribution of Cu-Kα was due to the medium range X-rays, nonetheless, hard X-rays with energies greater than 15 keV also participate in the process. The total emitted X-ray energy in the forms of Cu-K and Cu-K/3 was around 0.14 ± 0.02 （J/Sr） and 0.04 ±0.01 （J/Sr）, respectively. The total energy of the emitted hard X-ray （〉 15 keV） was around 0.12± 0.02 （J/Sr）.

Reducing Radiation Dose by Using Pulse X-Ray Apparatus

Pulse X-ray diagnostics is capable of reducing the radiation exposure considerably. As for pulse X-ray diagnostic machines, which form pulses with the duration of 0.1 μs, using them one can get outstanding results in this area. This fact can be explained by the long period of luminophor persistence in intensifying X-ray luminescent screens. In this paper we present experimental data, comparing radiation doses, measured at pulse X-ray apparatus and apparatus of constant radiation.

Reduction of the Radiation Dose by Decreasing the Tube Current without Degradation of Low-Contrast Detectability on Abdominal Multi-Detector Row CT: A Phantom-Based Study

As use of the lowest acceptable radiation dose during routine diagnostic imaging is important, we determined the optimal tube current without degradation of low-contrast detectability on abdominal multi-detector row CT (MDCT). CT scanning was performed with a Catphan®?500 phantom. The optimal tube current was 300 mA on 64-MDCT and 160 mA on 8-MDCT, with a fixed voltage of 120 kV. Reduction of the radiation dose in abdominal CT scanning by lowering the tube current proved to be feasible.

In-situ observation of porosity formation during directional solidification of Al-Si casting alloys

In-situ observation of porosity formation during directional solidification of two Al-Si alloys (7%Si and 13%Si) was made by using of micro-focus X-ray imaging.In both alloys,small spherical pores initially form in the melt far away from the eutectic solid-liquid (S/L) interface and then grow and coagulate during solidification.Some pores can float and escape from the solidifying melt front at a relatively high velocity.At the end of solidification,the remaining pores maintain spherical morphology in the near eutectic alloy but become irregular in the hypoeutectic alloy.This is attributed to different solidification modes and aluminum dendrite interactions between the two alloys.The mechanism of the porosity formation is briefly discussed in this paper.

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.

Phase-contrast Imaging Simulation Based on a Micro-CT System

Propagation-based phase-contrast imaging was simulated based on paraxial Fresnel-Kirchoff diffraction integral and spherical wave illumination. Under a developed micro-CT system parameters, the effects of focal-spot size and imaging geometry on phase-contrast imaging have been investigated using a 2-mm-thickness polystyrene edge phantom. An equivalent mono-energy was used to substitute the polychromatic spectrum of the micro-focus X-ray source. To consider effects of focal-spot size and detector resolution, the obtained phase-contrast image with an ideal point source was convolved with source intensity distribution and point spread function of detector. Simulations show reasonable influences of the two parameters which are in good agreement with experimental results.