They make monitors specific to your purpose, and they cost a pretty penny. From my understanding these types of monitors are not the best for colors or motion, but incredible for grey-scale still images.
The manufacturer of you X-ray machine should have recommendations. What's the resolution of the pictures? It should be an non-glare display and probably pre-calibrated to display the gray scales properly, like the Dell UltraSharp U2713H
They make monitors specific to your purpose, and they cost a pretty penny. From my understanding these types of monitors are not the best for colors or motion, but incredible for grey-scale still images.