Questions to consider before buying a 3D printer

[curious aardvark]

couple of things:
1) you absolutely need to know what your budget is. Metal printers start at around the $50,000 mark.

2) sla and fdm are probably not going to be much use to you, other than for 'rough' prototyping. For final use you'll most likely need a nylon powder based sls system - starting at around the $10,000 mark.
A polyjet system might also be suitable as they tend to have more available materials.

3) for small parts like the nozzle thing you posted the picture of - scanning is not the way to go. Simply design from scratch. Looking at that part, it would take about an hour for me to replicate with a set of digital calipers and my cad software. It would take much much longer to try and get an accurate scan and convert it into a model. And even then it would be nowhere near as accurate as the designed from scratch model.

4) there is software that can convert mri/cat scans into printable 3d models. For things like eye sockets - that's currently your best option. Or as awerby suggests possibly use a soft silicon to make a mould.

Industrial quality scanners start at around the $20,000 mark.
For most 'things' it is quicker and more accurate to design from scratch.

But you need to get a definite top end of your budget before you can even begin to start considering equipment.