? First Y90 isn't a natural isotope and quickly decays to Zr90. It's Radiogel (Y90 dispersed in gel that solidifies at body temperature) that is now well over two decades old. The sad fact is to date Radiogel hasn't helped a single human because until 2023, RDGL didn't do the obvious to verify containment were applied: direct imaging of Radiogel placement over 10 days or so.