1. A method for visualizing a body volume, wherein a data set whose data values represent said body volume is displayed on a display unit two- or three-dimensionally, in which method: a synthesized representation is calculated from at least two selected diagnostic data sets which are not identical and have a predefined spatial allocation with respect to each other, wherein each of said data values of said synthesized representation is calculated as a mathematical function of at least one data value of each of said selected data set, and said synthesized representation is displayed on the display unit, wherein it is established by way of a criterion for each pixel of a selected data set whether said pixel is assigned to an image background or not, and those pixels which are assigned to an image background are not taken into account when calculating the synthesized representation.