Radiologists overlook 1/3 of cancer cases. This may sound sensationalist but it came from this study outlined at ScienceDaily.com. Here is the full quote:
When people are asked to search for an item that will appear only once in 100 images, they might miss as many as a third of the objects they're supposed to be finding. Studies of radiologists looking at images to find cancer have shown similar error rates.
I think this fact provides new evidence in support of the use of computer aided diagnosis (CAD). It is happening but the progress is very slow. Screening seems the most appropriate starting point. It could be cancer or blood work (see the article on cell counting).
"Fortunately for the bottom lines (and bottoms) of radiologists everywhere, medical image analysis seems to be a lot tougher problem than top-40 musical analysis." 
Other image analysis examples