I prefer the Canon Digital SLR camera's with a fixed (non-zoom lens 50mm). You do not need a top of the line camera body most of my clients are using the Canon Rebel base model, or the Nikon Digitla SLR base model.
If you want have publication quality photos that adhere to the ASPS Photographic Standards you will also need off camera lighting and system for taking the photos from the same position when doing before and after shots.
Most of the doctors websites have photos that are out of registration with yellow or blue color cast.