The concept of "x-ray" is generally just fingerspelled.
But you may see some people do a version of the sign that uses an "X" hand and then shows a ray of light.
X-RAY (version 2)
Show the fingerspelled letter "X" then hold up a "crushed-O" hand (aimed downward and to the center) and move the hand downward and to the center as you open it up into a palm-down "5-hand." What you are doing is using a version of the sign for "beam or ray of light" to represent the "ray" portion of the sign.
Like I said, most of the time we just spell "x-ray." The "X" + "ray of light" version could be useful for certain situations in which you might want to show exactly what is being x-rayed by aiming your beam of light at a particular body part or area of the body.
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