X-ray Digital Radiography Research Articles

The function-transferring model construction for X-ray digital radiographic system

This paper is aimed at presenting a renovated model-building method of transfer function for industrial X-ray digital radiography based on the amorphous silicon X-ray flat-panel detector. The system, known as point-spreading function (PSF), is composed of three parts: the system geometrical dispersion with a non-spot power source, the scintillating screen dispersion and the aperture sampling of the pixel detector. For the innovation purpose, we have first of all established a mathematical simulation of the PSF and the modulation transfer function (MTF) on the basis of analyzing the intensity distribution of X-ray penetration area in each part and by taking Gaussian functions as a mathematical equation for depicting the transfer behavior of each part of the system. And, then, we have worked out the approximately effective bandwidth of the system from its half-wave width. And, finally, by taking the digital radiography based on the flat-panel detector for sampling, the paper has provided a theoretical foundation for the industrial X-ray radiographic testing and measurement operation. In addition, the author has also estimated the validation of the model through experiments and proved that the method helps to make high resolutions of the diacritical tiniest details in the work-pieces, which has shown and will show its technical rationality, technical appropriateness and practical working value.

An X-ray system for visualizing fluid flows

A unique flow visualization facility, based on X-ray imaging, has been developed to study, characterize, and measure various flow characteristics in large vertical systems that have internal diameters of up to 32 cm and are as tall as 4 m. This facility provides digital X-ray radiography and stereography imaging to visualize and time-resolve 3D flow structures in multiphase and opaque fluid flows at up to 60 frames/s. In addition, X-ray computed tomography (CT) imaging records local time-averaged phase distributions in multiphase flows with a spatial resolution of less than 0.5 mm (∼0.15% of a 32-cm-diameter object). The X-ray hardware and image processing software for this facility are described. Selected imaging results are then presented for various single and multiphase fluid flows.

Monitoring Microstructural Evolution, Crack Formation, and Damage Characteristics near Crack Tip in a Highly Filled Elastomer-Using Digital Radiography X-ray Techniques

In this study, the change of microstructure, the formation of cracks, and the change of damage characteristics near the tip of a propagating crack in a highly filled elastomer containing hard particles embedded in a rubbery matrix were investigated using digital radiography X-ray techniques. Experimental findings reveal that the degree of inhomogeneity of the material's microstructure and the number of non-propagating cracks increase as the applied strain is increased. Also, the damage characteristics near the crack tip are highly dependent on the loading history.

Instruments and detectors on the base of scintillator crystals ZnSe(Te), CWO, CsI(Tl) for systems of security and customs inspection systems

Results of experimental studies of detector arrays scintillator-photodiode (S-PD) and scintillator-photoreceiving device (S-PRD) used for X-ray digital radiography have shown that there exist further possibilities to increase spatial resolution of this system up to 2–3 line pairs per mm. Theoretical analysis and experimental studies show that the two-energy detection method not only allows one to detect organics on the background of metal, but also substantially increases (by 3–5 times) the detection ability of the system as a whole, especially if parameters of the S-PD pair are optimized, in particular, when ZnSe(Te) is used in the low-energy circuit. A possibility to distinguish, in principle, between substances with insignificant differences in atomic number has been theoretically proven—by transition to multi-energy radiography. 3D-imaging has been realized using S-PD detector arrays. On base of theoretical and experimental search was installation of several types of inspection systems for control objects with square size 0.4×0.6–2.5×3.5m.

High-speed digital radiography using structured CsI screens

We report on the development of a high-speed digital X-ray radiography system based on a microcolumnar CsI(Tl) scintillator optically coupled to a CCD. The new system is capable of acquiring 248 × 248 pixel images at the speed of 100,000 frames per second. The performance characteristics of CsI(Tl) screen in relation to the high-speed X-ray imaging requirements are described and compared to those of a commercial screen (Gd 2O 2S(Pr)). Additionally, representative X-ray imaging data acquired with the CsI(Tl) screen at 100,000 fps are presented.

X-ray radiation detectors of “scintillator-photoreceiving device type” for industrial digital radiography with improved spatial resolution

Main types of photoreceivers used in X-ray digital radiography systems are luminescent screens that transfer the optical image onto charge collection instruments, which require cooling, and semiconductor silicon detectors, which limit the contrast sensitivity. We have developed and produced X-ray radiation detectors of “scintillator-photoreceiving device” (S-PRD) type, which are integrally located on the inverse side of the photodiode (PD). The receiving-converting circuit (RCC) is designed for data conversion into digital form and their input into PC. Software is provided for RCC control and image visualization. Main advantages of these detectors are high industrial resolution (3–5 line pairs per mm), detecting activity up to 20μm, controlled sensitivity, low weight and small size, imaging low (0.1–0.3mrad) object dose in real time. In this work, main characteristics of 32-, 64- and 1024-channel detectors of S-PRD type were studied and compared for X-ray sensitivity with S-PD detectors. Images of the tested objects have been obtained. Recommendations are given on the use of different scintillation materials, depending upon the purpose of a digital radiographic system. The detectors operate in a broad energy range of ionizing radiation, hence the size of the controlled object is not limited. The system is sufficiently powerful to ensure frontal (through two walls) observation of pipelines with wall thickness up to 10cm.

Thick films of X-ray polycrystalline mercuric iodide detectors

Polycrystalline HgI2 thick film detectors are among the leading semiconductor materials to be used as direct converters in X-ray digital radiography. Their properties along with a survey of the properties of alternative materials, such as PbI2 or A-Se, will be given. The preparation of HgI2 detector plates, both by direct evaporation (Physical vapor deposition, (PVD)) and by binding the individual crystallites with polymeric glue, forming screen-printed (SP) detector plates, will be described. The microstructure of the PVD thick films showing a columnar morphology, as determined by SEM measurements, will be shown. The X-ray response to radiological X-ray generator of 85kVp using the current integration mode will be reported for both PVD and SP films. Finally, some X-ray images taken at Xerox–Parc using HgI2 polycrystalline detectors will be shown.

Digital radiography using an EBCCD-based imaging device

In the last few years, large efforts were devoted to the development of new intensified imaging systems to be applied mainly in medical radiographic devices for the reduction of the dose irradiated to the patient but also in high-energy physics for particle tracking or in astronomy for low-light imaging. Among a number of different image-intensifier systems, electron-bombarded charge coupled devices (EBCCD) present interesting characteristics providing the opportunity to be used also for special application such as X-ray imaging in industrial field. For this purpose, a prototype EBCCD image-intensifier tube suitable for X-ray digital radiography (DR) and computed tomography (CT) has been set up by the Physics Department of the University of Bologna (Italy) and Geosphaera Research Center of Moscow (Russia). Results concerning tests of EBCCD device and DR analysis of industrial components are presented and discussed.

Optimization of Cd1–xZnxTe Detectors for Digital Radiography

In this study, measurements of the electrical and detection parameters of the Cd1-xZnxTe detectors, within the x-ray diagnostic energy range, have been performed with the aim of optimizing the image quality parameters of these solid-state-ionization detectors. Namely, the leakage current and system capacitance of the x-ray imaging system have been measured as they relate to signal parameters. Similarly, the detected signal and noise contributions were measured and related to the radiation exposure and tube current setting. Furthermore, the detector contrast has been experimentally determined. The experimental results indicate that Cd1-xZnxTe detectors have low leakage current, high resistivity, and high detector contrast resolution. Therefore, they appear to be very attractive for imaging applications with applications in x-ray digital radiography.

Experimental study of LEC GaAs detectors for X-ray digital radiography

In previous studies, various semi-insulating LEC GaAs crystals were irradiated with photons in the diagnostic energy range (20–100 keV), in view of a possible application in digital radiography. Solid-state and irradiation measurements, together with Monte Carlo simulations, have indicated good candidates for this application among the crystals we have investigated. In this paper we present results concerning the detection characteristics (detection efficiency, charge-collection efficiency and energy resolution as functions of the bias voltage) of one of these materials and the images obtained by a pixel detector made on the same material and a bump-bonded electronic system.

Electrical characterization and detector performances of a LPE GaAs detector for X-ray digital radiography

The electrical characteristics of a LPE n-type GaAs crystal have been fully measured. The experimental results were used to build a model, including the parametrization of the electric field inside the crystal, and to study the features of such material as a detector in view of a possible application for digital radiography. The predictions of a Monte Carlo based on this model are in very good agreement with the measured performances of this crystal when used as a detector for X-rays in the diagnostic energy range.

48938 In process characterization of gallium arsenide crystals by X-ray digital radiography and computed tomography : Nondestructive Characterization of Materials IV. Edited by C.O. Ruud, J.F. Bussiere and R.E. Green. pp. 179–186. Plenum Press (1991)

48938 In process characterization of gallium arsenide crystals by X-ray digital radiography and computed tomography : Nondestructive Characterization of Materials IV. Edited by C.O. Ruud, J.F. Bussiere and R.E. Green. pp. 179–186. Plenum Press (1991)

Comparison of different GaAs detectors for X-ray digital radiography

Two different GaAs crystals, one LEC and one LPE, have been irradiated with photons of various energies, to compare their response in view of a possible application for digital radiography. Experimental results include I–V curves, charge collection efficiency, detection efficiency and energy resolution as a function of bias. A comparison is made with a simulation program that takes into account X-ray interactions, electric field and charge trapping inside the material.

Evaluation of elemental and compound semiconductors for X-ray digital radiography

We present a comparative study of the performance of elemental and compound solid state crystals of possible use in X-raY digital radiography. The general purpose EGS4 code was used to simulate photon-electron transport in the energy range 20 to 60 keV. The efficiency and the energy resolution, as a function of X-ray energy, are calculated and correlated to the different physical characteristics of the crystals considered.

Use of EGS4 for the evaluation of the performance of a silicon detector for X-ray digital radiography

The general-purpose EGS4 code has been used to evaluate the efficiency, the energy and the spatial resolution of a silicon crystal with double-side microstrips readout to detect X-rays in the diagnostic energy range (10–100 keV). A single crystal configuration, a sandwich arrangement with a high- Z converter foil in between two crystals and a multicrystal configuration have been investigated. The simulation with a low energy spectrum X-ray beam and a breast phantom has shown that this type of detector would be of valuable use in mammography applications: breast calcification with a diameter smaller than 500 μm can be easily identified.

Comparison between digital radiography and conventional X-ray radiography in the diagnosis of lung cancer

Comparison between digital radiography and conventional X-ray radiography in the diagnosis of lung cancer

Quantitative Diagnosis Using X-ray CT and Digital Radiography

Quantitative Diagnosis Using X-ray CT and Digital Radiography