Its space. When it comes to radiation, an X-Ray machine is by far the least of their worries. Astronauts come back from space missions utterly glowing with radiation.
Admittedly the cancer rate amongst astronauts isnt THAT much higher (just under 1/3 of astronaut deaths compared to just over 1/5th of the general population), but this is also a cohort that have mostly been non smoking tea-totaller health conscious non-junk-eating people so its definitely a thing.
Like yeah, over exposure to medical X-Rays is totally a risk factor, but astronauts go into space knowing that space is actively trying to radiate them, freeze them, burn them, pop their lungs, boil their blood and suffocate them. Its a soldiers gambit really.