I think these machines will not be able to give 100% accurate result. In studies of this type there will always be errors. But even if this percentage of accuracy is high, then this will benefit humanity.
I'm not knowledgable enough to say if these machines will work fine or not.
I'm more thinking about the morality of the system. Imagine this machine tells you that you may have cancer on an airport.. before a very long flight ... what would go through your mind?