Discriminability of selected periods III‒IV elements in photon-counting computed tomography using a pixelated CdTe detector

This study introduces a new approach in photon-counting computed tomography (CT) for elemental discrimination in periods III and IV of the periodic table of elements, which have not been covered by conventional methods that rely on the K-absorption edge of the target element. The present method features a pixelated CdTe detector with positional sensitivity and energy resolution. The authors changed its energy threshold level to determine the worthiness of counting an energy deposition by an X-ray photon in a pixel rather than changing the tube voltage in accordance with the target element as in the conventional method. The differences between the images are visualised on a scatter plot against various threshold levels, which clearly separates iron (atomic number 26) and copper (atomic number 29) with minimal overlap after normalising the CT values of aluminium and air to 0 and -1000, respectively. The discriminability was quantified using the Bhattacharyya coefficient. This elemental discrimination method does not rely on the K-absorption edge of the target element and can therefore be broadly applied to other elements in non-destructive (non-invasive) industrial and biomedical CT inspections.