I just checked with one of our Nuc. Med. Techs for confirmation: most Nuc. Med. programs (yes there are organized programs) require one be a Radiologic Technologist ("Rad. Tech") in order to be considered for the program. Check out your particular state requirements.
Also, the Rad Techs, while licensed in a particular state, also must pass a national exam, which the administering governing body is fast moving towards the Nuc Med techs obtaining a Bachelor's degree from an accredited Nuc Med program.
I suggest if you're interested, to do an online search for Nuc Med programs in your state/area, and then inquire about their respective requirements.
You may need to decide between being an RN and being a Rad Tech/Nuc Med Tech, depending on how much time and $$ you want/are able to invest in education. You won't be able to work as both, simultaneously, even though having an RN makes you a more valuable part of the team, IMO. (Also, no facility will pay you double wages for your RN; you'll receive the Nuc Med Tech pay, if you are hired/work in that capacity.
An RN's scope of practice and focus is very different from that of a Nuc Med Tech (I highly respect both!
Check into both, and I wish you luck. --- D