Claustrophobia is defined as an intense, irrational fear of enclosed or confined spaces, often triggering anxiety, or panic attack attacks, which can occur in places like elevators, tunnels, or crowded areas. 

I must admit that I am a sufferer of claustrophobia and recently I had reason to undergo a PET scan. 

The closest I can analogize, was like leading the lambs to the slaughter. I had no idea that the scan involved an MRI like tunnel and, after an hour of chemical preparation, I was shown into a room where I encountered a torpedo shaped funnel, and was told that the scan would occur therein.

With my history and propensity, my anxiety began to build, and when I tried it out, I was cautioned that my arms had to be restrained to avoid movement.

No way!

Needless to say, I bolted and now I face a return engagement. I will be better prepared mentally and physically for a fear I know I must conquer.