X-ray machine vision is used throughout the short story to scan the belongings of subway passengers in America. The X-ray machines not only scan objects, but also rematerialize them and strip them of any danger. The protagonist learns from a colleague about how the X-ray machines actually work, and fantasizes about avoiding them.
One time, Hoffman told me that the machine they use at security checkpoints isn’t really an x-ray machine. The government confiscates everything you put in; whatever emerges from the machine may look indistinguishable from what went in, but it has in fact been reconstituted. Atom by atom, the new objects are assembled, printed, and returned to the passenger. The process takes but an instant because our technology is so advanced. The new objects conform perfectly to the new American national security standards, with all elements deemed dangerous removed. If the objects contained any gasoline, it would be turned into water; if there were a gun, the bullets would be turned into rubber; if a computer contained harmful knowledge, it would be deleted and replaced with sanitized information.