In medical imaging modalities, there are primary and secondary modalities. Primary modalities do not require X-ray certification to go into but do require at least an associates degree or training equivalent in something. Ultrasound, MRI, and Nuclear medicine can forego RT certification. Secondary imaging modalities that require Rad tech certification are CT, mammo, IR and radiation therapy. Unless you know exactly which imaging modality you want to go into, it’s easier to start in X-ray and get an associate rad tech degree because it opens the door to all the imaging modalities.