CAT Trap

Imagine you're being forced into a gravelike tube made of strong and hard metal, that you cannot escape. It doesn't matter whether you protest or not. Once there, you're subjected to uncomfortably bright light, and ominous, threatening, loud sounds fill what little air you have left for breathing.

A stock element of horror and thriller media: As part of a medical examination, the protagonist is put in a CAT, PET or MRT scan tube. Cue the ominous loud sounds those machines make, and possibly some claustrophobia-induced nighmarish visions. Bonus points if the subject is already claustrophobic, paranoid or otherwise psychologically fragile. Extra bonus points if the tube turns out to malfunction in some hellish sort of way.

Note that this is about the claustrophobic imagery and feeling itself, not about what caused it or where it leads.

It's Truth in Television for people with actual claustrophobia.

If there are actual ghosts involved, this occurs as an illustration of Haunted Technology.

Might overlap with Artifact of Doom. Can have It Won't Turn Off as a side-effect.

Has naught to do with Ghost in the Machine or Ghost in the Shell. Not necessarily connected to Digitized Hacker, though the potential is there. Nothing to do with standardized testing either.

Examples of CAT Trap include:

Film

In Ghost In The Machine, while a serial killer is undergoing a CAT scan at the hospital, a surge of lightning courses through the building, and his soul is transformed into electrical energy. He then uses the electrical grid and computer networks to continue his killing spree.
The Exorcist had a variation - as one transcript puts it, a huge machine, two pieces on either side of Regan's head and a piece above
The Broken
The mentally ill girl in Dark Floors (the Lordi monster film) is put into a CT machine and shortly thereafter begins to freak out. It's also where she starts when the monsters make the night start over again, something only she can remember.

Live Action TV

Inverted in Scrubs where Elliot claims she uses a broken MRI machine as her "own little coccoon" when she's feeling stressed.
In The X-Files episode "Theef", the poor doctor's poor wife is literally grilled in one of those.
One of the challenges in Gaki no Tsukai involves a MRI scan. And has the contestants terrified.

Video Games

One full level of Condemned 2 was a hallucination you had while in a CT tube.

Real Life

For many people, claustrophobia is perfectly real, and a CT or MRI tube can easily trigger that. That's why they developed the Open MRI.