1. An x-ray/gamma ray imaging apparatus, the apparatus including a pixilated x-ray/gamma ray detector comprising a detector member configured to detect incident x-ray/gamma ray wavelength photons a position for a body under test, an x-ray or gamma ray source, and a structure configured to perturb the energy spectrum, each lying on a common axis, wherein the source is arranged to direct an x-ray/gamma ray energy spectrum along the common axis to impinge upon the structure configured to perturb the x-ray energy spectrum, and a positioned body/object under test, wherein said structure and the position for the body under test lie between the source and the detector member wherein the said structure comprises at least three adjacent regions, each region different to immediately adjacent regions and configured to perturb the x-ray energy spectrum differently, wherein the difference between adjacent regions includes at least one of: thicknesses of material forming adjacent regions; the presence of material forming adjacent regions; and the type of material forming adjacent regions, the apparatus further comprising image processing software and a database, wherein the database stores information indicative of at least one of: material type; material thickness; and material type and thickness, said information related to the effect of an x-ray/gamma ray energy spectrum of a similar source on a combination of the structure and the at least one material over period of time sufficient to allow the centre of fluctuation of the x-ray/gamma ray energy spectrum to be ascertained, wherein the structure comprises repeating arrays each array comprising the at least three adjacent regions, each region different to immediately adjacent regions and configured to perturb the x-ray energy spectrum differently, and wherein the image processing software is configured to execute a materials identification algorithm to determine a selected one of: the material type; the material thickness; and the material type and thickness of the body through which the x-ray wavelength photons have passed, and wherein the image processing software compares outputs of pixels of the detector with information stored in the database and processes the outputs of the detector according to a noise reduction algorithm that uses information from the database.