Hey Craig, if you don't recall a specific reason for why the x-rays are being done, then it's probably for monitoring only. Your rheumy has this new toy and is probably having all of her mtx patients do the x-rays. I wish my rheumy had a digitial x-ray machine.
MTX lung is not good, but it is very rare. If you're not having any lung sx, don't worry about it.
El