A few points:
- Most radiologists dictate into a system that has pre-set templates. So they're really only dictating a few specific words/phrases.
For the radiology dictation software, it is (I believe) actually voice recognition software. So it recognizes your voice, adjusting for your accent.
- Keep in mind that, even among radiologists for whom English is their native language, there is a huge variety in accents and pronounciation. Despite that, they all seem to manage just fine.
- All doctors dictate, not just radiologists. I am a non-radiologist, but I still dictate discharge summaries, admission H&Ps, etc. For that, it actually IS a question of transcription, so we are asked to speak slowly and to enunciate.
If you want to be a radiologist and English isn't your native language, you'll be fine. I've seen quite a few radiologists who spoke English with an accent, and they didn't seem to have major problems..