1. A method for facilitating comparison of image data from a given medical imaging protocol with archive image data, comprising: obtaining subject image data from a scan of a subject using the medical imaging protocol; obtaining archive image data differing from the subject image data in a given variable; determining a modifier usable to reduce the difference between the archive and subject image data; using the modifier to modify one of the subject image data and the archive image data to reduce the difference; and comparing the modified archive or subject image data with the subject or archive image data.