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.
You can learn
American Sign Language (ASL) online at American Sign Language University ™
ASL resources by Lifeprint.com © Dr. William Vicars