X-ray
X-rays or X-ray radiation was a high energy type of electromagnetic radiation. X-ray photons were used for medical and dental imaging, as well as weapons systems. They are also produced naturally by a variety of stellar phenomena, including pulsars and quasars.

Gosis' species used x-rays to get a look inside a lifeform. In 2152, Temec created a radiograph of Captain Jonathan Archer by using x-rays. ()

In 2364, Wesley Crusher reported that the deflectors of the  were being hit by X-rays. Worf adjusted the settings to compensate for the rays' effect. ()

Talarian warships used lasers that emitted x-ray radiation. ()

While working on a way to separate Tuvok and Neelix following their transporter accident, The Doctor referred to the use of barium as a contrast agent for the "primitive imaging technology called X-rays." ()

In 3190, the NSS T'Pau observed the Dark Matter Anomaly give off a spike in X-ray radiation before it unexpectedly dispeared, reappearing seconds later a thousand light years away. ()

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de:Röntgenstrahlung
Medical procedures
Radiation