Considering how oblivious some companies are to the difference between $0.02 and 0.02 cents, milli and micro might be way beyond the ability of some TSA technicians to understand.
Of course these new machines cannot fail the exact same way as the Therac 25. But could they fail in a new, unpredicted way? I dunno. I am not familiar enough with how the backscatter machines are implemented to be able to predict how they could fail. But I maintain neither are most of the people who defend these machines as safe.
http://usatoday30.usatoday.com/yourlife/health/healthcare/go...
I think "nobody would notice" is a pretty accurate description of what would happen in that case.