You could look in the private sector, this is where most of the action in medical imagery happens. Note it is often noted as radiology but it is now much more than this.
Company such as
The biggest trade show about radiology in the Americas (possibly the world) is organized by the RSNA and is held every year around the american thanksgiving. A good place to get an almost complete list of companies involved in some way with medical imaging would be to look at the list of participating exhibitors. It will give you a good starting point to investigate these companies, their offering and by looking at the kind of jobs they are looking you will get a feel of the technology behind the solution.
Another alternative is to go for research. Many universities and colleges have programs that deal with some aspects of medical imagery. You could get a job there as a research assistant or as programmer to assist the researcher with implementing their solution. Many of them are brilliant with their ideas but have very poor skills at implementing them. The end results is that many very good ideas die because they cannot get the code right.
There are also countless start-ups and smaller companies that do a lot of great work, though these will require a bit more research on your part.
It is a vast and very interesting field of work for programmers to be in. Most system dealing with radiology will employ a very divers array of skills ranging from vanilla database driven system, integration of heterogeneous systems all the way to very deep 3d modelling and complex math algorithm. Whatever your skill set I'm quire sure you will find your match. Also you can always get in the company with a certain skill set and gain access to more interesting challenges from the inside.
I hope this helps, I wish you best of luck.