Actually, there is a lot of conflicting information online, but the official AIIMS prospectus is quite clear. Yes, you are eligible, provided you meet the specific subject requirements.

However, some websites claim you need a B.Sc. in Nuclear Medicine specifically, while AIIMS allows candidates from allied or related subjects to apply. Your B.Sc. in Radiology (http://b.sc) and Imaging Technology falls directly into this "allied" category