In a computed tomographic imaging method and apparatus a subject in an examination region (14) moves axially as an x-ray source (12) rotates therearound. Views corresponding to a spiral path around a volume of interest in the patient are sampled, interpolated (46), and reconstructed (54) into a three-dimensional image representation (56). This process is repeated a plurality of times to generate a plurality of three-dimensional image representations of the same volume at time displaced intervals. The plurality of image representations are temporally interpolated (120) to generate a series of image representations, each one of which represents the same time or time intervals, i.e., a four-dimensional image representation that is linear in all four dimensions. A contrast agent may be injected into the patient such that the data represents the movement of contrast agent through the volume of interest. A reference image representation (126) of the volume of interest with no contrast agent is subtracted (124) from the four-dimensional image representation to generate a four-dimensional image (128) of the movement of the contrast agent through the volume of interest.