the new scanners would find an underwear bomb (tm). Obviously one could design experiments to find out, given access to a machine, operator, and clever IED.
So: obviously the Fed's machines cannot detect an artfully concealed bomb of sufficient size to down a pressurized airliner. Otherwise, they'd publish the evidence.
Sometimes "no comment" is a comment.
I saw a transmission x-ray machine being advertised as revealing all the bodily cavities. Nice. Obviously a transmission vs. backscatter machine is like gamma to alpha rays.