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Design and Assessment Principles of Semiconductor Flat-Panel Detector-Based X-Ray Micro-CT Systems for Small-Animal Imaging
Published in Iniewski Krzysztof, Integrated Microsystems, 2017
Alejandro Sisniega, J. J. Vaquero, M. Desco
In the development of x-ray micro-CT systems, most approaches make use of detectors based on x-ray image intensifiers and charge-coupled devices (CCDs) to which a scintillator screen is connected either directly or using light guides (e.g., fiber optic plates) [7–9]. Recent developments in semiconductor detectors have made it possible to use new, compact devices—flat-panel detectors—for x-ray detection. These flat-panel devices can be categorized into two different groups according to the process carried out to convert the x-ray photons (primary quanta) to electric charges that are gathered and converted into a digital signal. The first approach makes use of photoconductors that directly convert the incident x-ray radiation into electric charges as secondary quanta. Devices that conform to this approach are called direct conversion flat-panel detectors. The second approach is based on scintillation screens that stop incident x-ray photons, thus producing optical photons as secondary quanta. These optical photons are then stopped by a photodiode array that provides the electric charges required by the device readout electronics. The detectors that implement this scheme are known as indirect conversion flat-panel detectors.
X-Ray-Based Imaging
Published in John G Webster, Minimally Invasive Medical Technology, 2016
Digital detectors come in several different forms. Image intensifiers with CCD cameras, storage phosphor screens, and solid-state selenium drum detectors are either being used clinically or being developed. A recently developed type of digital detector is the flat panel detector, which consists of an X-ray sensitive layer and an active detector matrix (Kamm 1997). Flat panel detectors are of either direct or indirect type. Using the direct method, X rays are converted to charge by a semiconductor layer of selenium, and the active detector detects electric charge. Using the indirect method, X-rays are converted to light by a scintillator layer, and the detector detects the light and converts it into electric charge. In either case, activated cells in the two-dimensional matrix correspond to a given pixel location.
Dimensional Metrology for Industrial Computed Tomography
Published in Paolo Russo, Handbook of X-ray Imaging, 2017
Jochen Hiller, Thomas S. Miller, Peter Hornberger
Thereby, many hundreds of 2D X-ray projection images from different angles are acquired via object rotation in between the cone beam of X-rays. The complete scanning times are in a wide range from a few minutes up to a few hours, depending on the voxel size and the wanted accuracy of the dataset. The pixels on the 2D flat panel detector are able to convert the X-rays into an electrical signal. This signal is digitized, and in this way, the shape of the projected object (see Figure 47.5, left) can be visualized by a gray value coded image. Here we utilize the fact that the intensity of the X-ray beam is partially attenuated by matter. On the right of Figure 47.5, we see that the attenuation of the initial intensity I0 depends on the thickness d of the object and the linear attenuation coefficient μ of the material. Therefore, object regions with longer penetration length appear darker on the projection image. Hence, X-ray photons are attenuated exponentially and follow the so-called Lambert–Beer law of attenuation I(d,E,ρ,Z)=I0e−μ(E,ρ,Z)d where I is the transmitted intensity.
Deep Learning Based Steel Pipe Weld Defect Detection
Published in Applied Artificial Intelligence, 2021
Dingming Yang, Yanrong Cui, Zeyu Yu, Hongqiang Yuan
The real-time X-ray imaging system used in this paper is shown in Figure 2. The system mainly consists of a welded pipe moving part, HS-XY-225 X-ray machine, PS1313DX high-speed digital panel detector, image capture card, and display part. In the welded pipe moving part, the spiral submerged arc welded pipe is moved using a transmission vehicle with four longitudinal rollers fixed on the vehicle for rotating the spiral submerged arc welded pipe. The X-ray machine is fixed to the wall on one side and deep into the pipe on the other side, emitting X-rays that penetrate the weld seam. A flat panel detector absorbs the X-ray photons that pass through the weld, creating electronic data that retains information on the attenuation of the photons. An image capture card is used to convert the electronic data into a digital image sequence, which is then transferred to a computer for processing and display. Limited to hardware performance, only eight X-ray images per second can be captured and processed.