X-Ray Computed Tomography (XCT) Scanning Parameters Effects on the Hounsfield Unit (HU) Measurements for AA2011

Abstract

X-ray computed tomography (XCT) is a powerful technique that can detect internal defects and differentiate between different materials making XCT a valuable non-destructive evaluation (NDE). However, when X-ray CT is employed as an NDE method, the scanning parameters and methodology are often underreported leading to a lack of consensus on the optimal scanning parameters to use when analyzing a particular metal or alloy. In this study, 16-bit X-ray CT scans are employed to characterize AA2011. Four parameters are investigated: scan (voxel) resolution, tube voltage, tube current, and sample size (thickness). Two sample disks are scanned simultaneously at an image bit depth of 16-bit. Mean and standard deviation Hounsfield Unit (HU) values are calculated which are then used to develop a predictive model for these two values. The model equation is used to produce surface plots to determine desired scanning parameters combination for characterizing AA2011 HU mean and standard deviation values. It is concluded that higher scanning resolution (smaller voxel), larger tube voltage and tube current settings, and thicker samples result in smaller of standard deviation HU values and converged mean HU values when scanning AA2011.