Cathode ray and Fluoroscope

Cathode ray noun - A beam of electrons emitted by the cathode of an electrical discharge tube.

Fluoroscope and cathode ray are semantically related. in picture of inside a body topic. In some cases you can use "Fluoroscope" instead a noun phrase "Cathode ray", when it comes to topics like inside look.

Fluoroscope noun - An X-ray machine that combines an X-ray source and a fluorescent screen to enable direct observation.

Cathode ray and fluoroscope are semantically related. Sometimes you can replace phrase "Cathode ray" with "Fluoroscope", this terms are similar.