If for any reason you had to undergo a MRI, you should have a CD or DVD containing the information of this medical examination in a DICOM format (Digital Imaging and Communications in Medicine).
On Mac, two "free" applications are able to use and manipulate such format, iRad, and the well-known OsiriX which is now a reference in this field.
The new version of OsiriX is now available and this third opus is compatible with Leopard. This application is a perfect example how one can benefit from Mac OS X resources and layers while providing a typical easy to use Mac interface. One can even export data to iPod, or MRI specialists can even use iChat share display option to visualize results while lively commenting data.
A 64-bit Pro version of OsiriX is available for 149, it brings support for larger amount of RAM as well as higher performance