1. A medical viewing system comprising: an X-ray image acquisition device with a source of radiation and an X-ray image detection module; an image processor; and a display; wherein the image processor is configured for: retrieving a three-dimensional image data set, generating a first two-dimensional projection of the three-dimensional image data set corresponding to a first viewing direction; and overlaying X-ray images onto the first two-dimensional projection constituting a first view; wherein the image processor is configured for generating a second two-dimensional projection of the three-dimensional image data set corresponding to a second viewing direction constituting a second view, wherein a first viewing direction vector and a second viewing direction vector enclose an offset angle α, wherein the display is configured for outputting a combination of the first view and the second view with the same scale in a side by side manner, and wherein the image processor is configured for generating at least one reference line extending on the first view and the second view and corresponding to an edge of an intravascular device to be monitored by the medical viewing system.