[mr_mitm]

We call it "Röntgenstrahlung" (X-rays), "Röntgengerät" (X-ray machine), "Röntgenaufnahme" (X-ray picture). We even made a verb out of it, even though that's probably colloquial: "Wir müssen Ihr Bein röntgen" (we need to X-ray your leg).

[neuromanser]

Rentgen is a noun in Czech meaning 1. the machine, 2. the picture, the root of an adjective (rentgenový), Amd the root of a verb (rentgenovat).