A method processing an image dataset of radiation emergent from a test object after its irradiation by a suitable radiation source is described which comprises the steps of: generating an image dataset comprising a spatially resolved map of items of intensity data from the radiation emergent from the test object; further, resolving the intensity data items spectroscopically between at least two energy bands across the spectrum of the source; numerically processing the spectroscopically resolved intensity data items to determine a further spatially resolved dataset of data items representative of one or more orders of Compound Proton Number and/or effective mass thickness and/or a density; generating a segmented image dataset using the said dataset of data items representative of one or more orders of Compound Proton Number and/or effective mass thickness and/or a density. The method applied as part of a method for the radiological examination of an object and an apparatus for the same are also described.