Each state is different. Find the PA state Dental Assistant Association, or something like that, and see if you can find out information through that route. Here in New Jersey, to get your license you must first complete a ridiculously long course (25 hours lecture, 15 hours lab, then 30 hours of clinical work) before you can take the DANB or state dental radiography test, then assuming you pass it, you can apply for your state license. I just finished up the 4th week of my course. I'm taking a 3-hours/once a week/15 week course.
I hope for your sake PA is not as uptight about who they hand out x-ray licenses to.