There are three main branches of radiology that you can go into. There is general radiography, which is focused on using x-ray machines to create images and discover broken bones, diseases, tumors and the like. You might get an associates degree in general radiography or complete an x-ray technician certificate at a community college or technical/vocational school to get these sorts of jobs. Either way you will need to be licensed with your states radiation safety department and certified through the American Registry of Radiologic Technologists (ARRT).
Another radiography job that might interest you is the radiologic technologist, which is a slightly more specialized and higher paying job than the x-ray technician. Since you will need to learn some additional imaging techniques and have more responsibilities, a certificate program will not be sufficient. You will need to complete an associates degree in radiologic technology from a school that has been accredited through the Joint Review Committee on Education in Radiologic Technology. Then you can get licensed in your state and take the ARRT certification exam.
Ultrasound or nuclear medicine is the third career path in radiology you might take. There is a higher level of training required for this type of job than there is for both x-ray technician and radiologic technologist jobs. You will need to get an Associates of Applied Science in Sonography or Nuclear Medicine and sit for a challenging certification exam, and then go through the state licensing process just like all the other radiology career paths.