<unk>  is the oily contrast medium used for myelography. It's generic name is Iodophenylundecylic acid. It was introduced in 1944. It is no longer used today. A major drawback is the lack of resorption. Complete removal through aspiration is usually impossible after a procedure and the remaining droplets may lead to chronic irritation and severe arachnoiditis.
Patient #1: Remote history of having a myelogram
Pantopaque
Fair coin
Amnion
Ionic liquid
Floater
Wonder 
Sultiame
Wart