My entire scene for this final project is basically the heart... which is a very complex piece of anatomy to model accurately. I have used Mimics so far to sort through 240 slices of CT scans and create a heart. I then imported the heart into Maya and cleaned it up a bit. I tried extruding and changing some things, but the mesh that is on the heart is currently a mess so nothing was really matching up. I went with this for a while and created a plane slicing through the heart, showing the chambers. It is messy on the edges because I decided then to re-create the heart by hand and then "stitch" this plane into place.
So now I have taken my model into 3DS Max in order to create a mesh that I can actually work with. This process is called re-topology. It is quite tricky, but basically you create one polygon at a time over the existing object. I've almost completed this process... here are some screen shots.