Building on some of my previous worked that examined this topic in New York State, a team of researchers recently published its analysis of the diffusion of digital mammography in the US in the journal Cancer. Digital mammography went from being all but nonexistent in 2001 to nearly universal in 2014, as seen in this graphic:

The analysis looked at drive times from residences to facilities to see which areas were being underserved in 2014. These included rural areas and areas with majority Native American populations. Read the abstract here (the paper itself is behind a paywall for the moment).