NEW : ACLU says passengers ' detailed images violate privacy , not dignity . New machines use radio frequency to scan passengers for hidden objects . They 'll be used on passengers selected for secondary screening . FBI says blurred image , remote location of passengers protect privacy .
NEW : ACLU says machines ' detailed images violate privacy , assault dignity . New machines use radio waves to scan passengers for hidden objects . They 'll be used on passengers selected for secondary screening . TSA says blurred image , remote location of scanner protect privacy .