I recently had occasion to pick up a CD full of medical images and needed to display those images on my Mac. When Photoshop failed to support the DICOM format, a google search turned up OsiriX, a “100% Free DICOM/PACS Viewer for MacOS X”.
The GPL open source OsiriX medical imaging software worked exactly as promised: fast and easy-to-use. It read the data directly from the CD without fuss and loaded it into an interactive framework which, if you try to think like a radiologist, rather than a normal person, made perfect sense.
There are options out the wazoo. You can import data, export data and query the data database. You can work with two and three dimensional data and time series “4D” data for heart studies. You can adjust the color lookup tables, magnify, and mensurate. You can store pictures and source data on your iPod or burn data to recordable discs or produce a text report. In short, you can thoroughly inspect all kinds of radiological medical data in a well thought-out interface.
As a final note, I personally use a two-button scroll-wheel mouse on my Mac, which turned out to be exactly the right kind for this program. You can interactively assign the left and right mouse functions to manipulate the image while using the scroll wheel to move between images in a given series.
Read more about the OsiriX project over at Apple.