It is known that high dose X-ray irradiation increases the probability of cancer development in humans. Therefore, the dose decrease at every X-ray imaging event is a major goal, especially during CT tests, where the applied dose is generally a multiple of a few single radiographic imaging doses. Using narrow energy X-ray beams instead of wide energy X-rays has several advantages. First, it reduces the beam hardening effect, when the output beam (after the patient) is harder, i.e. it consists of a higher ratio of high energy X-ray photons than the input beam. Imaging with narrow energy X-rays also provides lower scatter noise than using wide energy X-rays. As a result we can obtain high signal to noise (S/N) ratio X-ray images while using much lower dose than with a regular x-ray beam. The paper points out how we can generate narrow energy X-ray beams by using special materials for which the K edge absorption peak falls into the diagnostic X-ray energy range. Furthermore, it will be shown that contrast agent materials such as Iodine are more effective when combined with the right K edge filter material.© (2011) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.