We have developed a full-scale image quality (IQ) simulation model as a tool for X-ray system design, image quality optimization and patient dose reduction. The IQ model supports the (de-)composition of system level requirements and simulates several types of automatic X-ray control technique. The model is implemented in LabVIEW. The X-ray system is modeled in distinguishable components and processes, which allows isolation of sub-systems and exclusion of devices. All relevant patient dose and IQ items such as contrast, sharpness, lag and noise are calculated and additionally combined in IQ "figures of merit" (FOM). Some characteristic application examples will be presented: In a general image magnification study we compare magnification techniques, such as geometric enlargement, image intensifier zooming and digital processing. In an optimization study we apply a new IQ FOM that contains not only imaging properties of the system, but also detail information in terms of material, size and thickness. Combining the IQ simulation model with a Pareto trade-off algorithm appears to be a promising optimization approach. In addition to the mentioned employment, the IQ simulation model is also suitable for comparison studies on the performance of flat detectors versus image intensifier television detectors, application related studies and fine tuning of specific settings and adjustments, design of test objects and development of measuring methods.