CT Multiscan: Using Small Area Detectors to Image Large Components

Abstract

The small size and dynamic range of the best two-dimensional X-ray detectors are impediments to the use of three-dimensional X-ray computed tomography (3D-XRCT) for 100 percent inspection of large ceramic components. The most common industrial 3D-XRCT systems use a “rotate-only” geometry in which the X-ray source and the area detector remain stationary while the component placed between them is rotated through 360 deg. This configuration offers the highest inspection speed and the best utilization of X-ray dose, but requires that the component be small enough to fit within the X-ray/detector “cone.” Also, if the object is very dense, the ratio of an unattenuated X-ray signal to that through the longest path in the component may exceed the dynamic range of the detector. To some extent, both of these disadvantages can be overcome by using “Multiscan CT,” i.e., scanning small overlapping regions of a large component separately while maximizing the X-ray dose to each. The over lapping scans can then be combined seamlessly into a single scan with optimal contrast.

Analytic reconstruction algorithms for triple‐source CT with horizontal data truncation

“…As we know, large field of view (FOV) CT imaging methods are attractive in both clinical/preclinical and industrial applications. Regarding the large FOV scanning configurations, the rotation-translation (RT) multiscan [15][16][17] and rotation-translation-translation (RTT) multiscan 18 are representative implementations in engineering. This kind of scanning usually is implemented based on a single source with fan-beam truncation in a horizontal direction.…”

“…This kind of scanning usually is implemented based on a single source with fan-beam truncation in a horizontal direction. The corresponding algorithms include BPF-type and FPBtype with appropriate data rebinning, [15][16][17][18] where the data rebinning step not only increases computational cost but also decreases reconstruction accuracy. Moreover, an off-set multiscan configuration and the corresponding BPF-type algorithm were reported, 19,20 which can achieve a larger FOV than the RT or RTT scanning configurations using the same equipment.…”

Reconstruction Method for Nonconcyclic Dual-Source Circular Cone-Beam CT with a Large Field of View

“…To solve this problem, several multiscan modes have been developed to acquire the complete projection data. Of them, the rotation-translation-translation (RTT) multiscan mode [1,2] and rotation-translation (RT) multiscan mode [3,4] are typical. In fact, RT and RTT multiscan modes not only acquire completed projection data, but can also reduce the differences of the flux intensities detected by different detector cells.…”

Characterization of Melt Infiltrated SiC/SiC Composite Combustor Liners Using Meso- and Micro-NDE Techniques

“…Use of small X-ray area detectors for computerized tomography data acquisition of large components has been demonstrated, using as components 20-cm-diameter CMC combustor liners (Sivers et al 1996). Figure 6 shows images of 3-mm-thick SiC/SiC CMC combustor liners and indicates how interior dekarninations are directly detectable.…”

“…Argonne National Laboratory (ANL) has been developing several NDE techniques primarily for mesoscopic (>0.2 mm) characterization of CMC material systems (Pillai et al, 1997;Spohnholtz 1999;Sun et al 1999;Sivers et al 1996). These NDE techniques include inflaredbased thermal imaging used to measure thermal diffusivi~, air-coupled ultrasound systems that do not require water coupkm~impact acoustic resonance methods for determining elastic modulus and darnping factors; X-ray imaging technology (primarily tomographic imaging) for verifying internal component damage, e.g., tbroughwall damage on turbine engine combustor liners, transition ducts, etc.…”