There is disclosed a method and apparatus for generating data for a two-dimensional image which identifies different classes of property of an imaged subject, this being done by separately rendering volumetric data classified into those different classes and, from all of those separate renderings, choosing one datum for use in the two-dimensional image as an image pixel. This being repeatable for each datum to be used in the two-dimensional image—thereby, for example, to selectively build-up the data for whole of the two-dimensional image as a mixture/combination of different classes of data. The data for the two-dimensional image may be colour coded for visually distinguishing data of different classes. Thus when applied to the image enhancement of tissues subjected to contrast agent uptake in patients kinetic information may be incorporated into the volume renderings to enable tissues of different enhancement and kinetic characteristics to be identified as such.