The invention relates to an imaging system for imaging an object, wherein the imaging system is adapted for scanning the object in accordance with a scan parameter. The imaging system comprises a projection image generation unit (15) for generating a two-dimensional projection image of the object. A model provision unit (16) provides a three-dimensional model of the object, and a registration unit (17) registers the three-dimensional model with the two-dimensional project ion image. A scan parameter determination unit (18) determines the scan parameter from the registered three-dimensional model.