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Semiconductor Sensors for Direct X-Ray Conversion
Published in Yallup Kevin, Basiricò Laura, Iniewski Kris, Sensors for Diagnostics and Monitoring, 2018
In general, radiation detectors can be operated in integrating or counting modes. In integrating mode, the charge information is sampled over an integration time and converted to a digital signal. In counting mode, the process in direct-conversion detectors, the total number of events is measured by counting the charge pulses, as illustrated in Figure 5.2. In addition to this, the energy of each absorbed photon can be obtained by measuring the total charge or pulse amplitude of each photon. Direct-conversion detectors thus offer a spectral resolution of the incoming radiation. The additional spectral information leads to the well-recognized benefits of photon-counting technology: lower noise, higher efficiency, and better spatial resolution. X-ray imaging applications benefit from direct conversion as it requires less image filtering to obtain the same image resolution or the same amount of image filtering to obtain better image resolution.
Industrial Radiography
Published in Paolo Russo, Handbook of X-ray Imaging, 2017
New applications take advantage of photon counting technology to improve the sensitivity (Walter et al. 2016). The image information is processed in the computer and a cross-section is reconstructed. Specialized tomographic routines were developed to reconstruct such a three-dimensional (3D) image of the weld (Redmer et al. 2006; Ewert et al. 2012a). This method is very sensitive to indicate cracks and lack of fusion. The depths and shape of these defects can be reconstructed and measured. Figure 30.29 shows the image of a reconstructed crack in an austenitic girth weld in comparison to a cross-sectional metallography.
Raman-Based Distributed Temperature Sensors (DTSs)
Published in Arthur H. Hartog, An Introduction to Distributed Optical Fibre Sensors, 2017
Photon counting, as implied by the name, is a set of techniques in which the detectors are designed to respond with a clearly detectable pulse when a single photon is detected. The output, being already in quasi digital form, suffers little further degradation in the subsequent parts of the signal chain, and very small power levels (in the aW regime) can be detected. However, these techniques are limited in the maximum signal that they can detect before overloading.
inHEART Models software – novel 3D cardiac modeling solution
Published in Expert Review of Medical Devices, 2023
Leah A. John, Brett Tomashitis, Zain Gowani, Dan Levin, Chau Vo, Ian John, Jeffrey R. Winterfield
inHEART Models provide an increasingly valuable tool for planning and executing safe and effective VT ablations. The system provides superb detail in scar characterization and in defining cardiac anatomy, particularly specific structures such as coronary arteries [13]. However, areas for improvement remain. One relates to the issue of CT-related noise which can sometimes impede necessary scar characterization. When there is a significant degree of noise or artifact, substrate characterization often becomes challenging, and scans cannot be adequately processed for interpretation. Currently, technological advances are being developed to address some of these issues and potentially lead to substantial improvements in imaging quality. The introduction of PCD-CT will take late iodine enhancement CT to a new level that could represent the future of cardiac imaging [37]. This new technology uses a direct conversion X-ray detector allowing for X-ray photon energies to be directly recorded as electronic signals. The use of a photon counting detector improves spatial resolution and iodine signaling while still allowing multi-energy imaging. This is particularly useful in cardiac imaging. Dual source PCD-CT allows multi-energy CT images of cardiac structures at high temporal resolution. Furthermore, PCD-CT permits energy thresholds to be set which eliminates noise and reduces artifact [38].