1. A method of inspecting a liquid article comprising: performing a DR imaging on the liquid article to generate a transmission image; determining from the transmission image at least one positions at which CT scan is to be performed; performing dual-energy CT scan at the determined positions to generate CT image data; determining a density and atomic number from the generated CT image data; judging whether at least one point defined by the density and the atomic number determined from the CT image data falls into a predetermined region in a two-dimensional space of density-atomic number; and outputting information indicative of that the liquid article is dangerous or not.