An x-ray/gamma ray imaging apparatus includes a pixilated x-ray/gamma ray detector (3) including a member configured to detect incident x-ray/gamma ray wavelength photons, a position for a body under test (2), an x-ray or gamma ray source (1), and a structure configured to perturb the energy spectrum (6), each lying on a common axis. The source is arranged to direct an x-ray gamma ray energy spectrum along the common axis to impinge upon a structure configured to perturb the x-ray energy spectrum and a positioned body/object under test. The structure and the position for the body under test lie between the source and the detector member, and the structure includes at least three adjacent regions, each region different to immediately adjacent regions and configured to perturb the x-ray energy spectrum differently. Detected photons are subject to a random noise reduction algorithm.
