1. A method for a separate three-dimensional representation of arteries and/or veins of a vascular system in an examination object based upon a tomography x-ray device, comprising: implementing a mask pass of the x-ray device with N projections at N angular positions about the examination object without a contrast agent; implementing a first filler pass of the x-ray device about the examination object with M measured projections at M of the N angular positions after an injection of a contrast agent, where M<N; implementing a second filler pass of the x-ray device about the examination object with N−M measured projections at N−M of the N angular positions directly following the first filler pass; reconstructing a composite three-dimensional volume data record from an intermediate data record, said intermediate data record being determined from the data records resulting from the mask pass, the first filler pass and the second filler pass by subtraction and combination; calculating a reprojection data record for arteries by reprojection of the angular positions of the first filler pass from the composite three-dimensional volume data record and/or calculating a reprojection data record for veins by reprojection of the angular positions of the second filler pass from the composite three-dimensional volume data record; and calculating a three-dimensional volume data record for arteries and/or a three-dimensional volume data record for veins by weighting the composite three-dimensional volume data record taking into account the respective measured projections and the respective calculated reprojections.