Medical diagnosis systems based on artificial neural networks Are there any medical diagnosis systems that are already used somewhere that are based on artificial neural networks?
Yes, there are many, actually. A Google search turned this paper Artificial Neural Networks in Medical Diagnosis (2011) by Al-Shayea up. 

Not only are they used in disease diagnosis, but even with things like prescribing medicines. In fact, the top project for a hackathon at my school analysed thousands of research articles, and took a patient's medication history as input, to best recommend them specific medicines. Check it out.