What elements compound is used to produce x-ray images?
An ordinary x-ray machine such as in medicine or an airport
scanner, consists of a cathode and an anode situated in an
evacuated glass envelope.
Once accelerating voltages are over 50 000 Volts, x-rays will be
generated at the anode.
Ordinary cathode materials suffice, and these commonly have a
tungsten heater, maybe with a thorium coating, for this material
emits electrons easily when heated.
The anode is the source of the x-rays, and commonly is angled
such that the x-rays emitted will not travel straight back to the
cathode. Because of the energies involved, the control of the
direction of the x-rays is rather limited (read very difficult) and
trying to focus the x-ray beam is indeed difficult.
Control of the beam is often accomplished by having a small
tubular opening in an x-ray opaque material, thus simulating an
attempt at collimation.
There are however x-ray sources that do not directly generate
their own radiation, they instaed encapsulate a radioactive source
which has inbuilt radiation properties. Cobalt 60 for example may
be a source of neutrons, and one common use of this high energy
source is for sterilizing medical equipment. Of course it is also
used as a source for medical x-rays as well. In appearance, this
material superficially looks like iron, and there has been at least
one incident where a C60 source has been recycled (along with other
scrap, in an horrific error) into reinforcing bars.
It may be that Cs137 is also used as an x-ray source, but my
brief search failed to find a reference.