1. A method for generating an at least three-dimensional display data set of a time parameter relating to chronological spreading of a contrast medium introduced into a vessel system, wherein a series of chronologically successive x-ray images of digital subtraction angiography from at least two different projection directions showing the chronological spreading of the contrast medium is used, the method comprising: determining a three-dimensional position for at least one correspondence point, correspondence region, or correspondence point and correspondence region defined, in each case, in at least one x-ray image of a projection direction; for each three-dimensional position, determining a time parameter assigned to the three-dimensional position, the determining of the time parameter comprising evaluating time-intensity curves assigned to the correspondence points or the correspondence regions over the series; and displaying the at least three-dimensional display data set formed from the three-dimensional positions with the assigned time parameters.