1. A method for automatic detection of a contrast agent inflow in a blood vessel of a patient with a computed tomography (CT) system, the method comprising: providing, using a computer device, statistical average values of principal components of a previous evaluation of a multiplicity of statistically comparable CT representations by, determining a multi-dimensional position of distinctive points of anatomical structures including a multi-dimensional position of at least one blood vessel or an ROI for the at least one blood vessel, carrying out a per CT representation principal component analysis, and calculating the statistical average values of the principal components; carrying out, using the computer device, a multiplicity of chronologically progressive scans in at least one section plane; progressively calculating, using the computer device, CT representations for respective datum; determining, for each CT representation and using the computer device, a multi-dimensional position of distinctive points of recognizable anatomical structures, except with regard to the at least one blood vessel or the ROI for the at least one blood vessel; determining, using the computer device, principal components for each CT representation; determining, for each CT representation and using the computer device, a deformation vector from the statistical average values of the principal components to the determined principal components; determining, for each CT representation and using the computer device, a transformation of the multi-dimensional position of the at least one blood vessel or the ROI for the at least one blood vessel; determining, using the computer device, a change in image values as a function of time in a region of the at least one blood vessel or the ROI of the at least one blood vessel over a multiplicity of the CT representations at respectively transformed positions of the at least one blood vessel or transformed ROI for the at least one blood vessel; and when a first threshold of the image values is exceeded, using the computer device to perform at least one of outputting the image values in the region of the at least one blood vessel or the ROI of the at least one blood vessel, and triggering an action.