On Friday, December 15, 2023, ASTRO submitted comments on the Nuclear Regulatory Commission’s (NRC) regulatory basis for their upcoming emerging medical technologies rulemaking. The regulatory basis serves as a precursor to the proposed rule, providing background, proposed policy, and technical changes to current regulations, and identifies different approaches to addressing regulatory issues. The rulemaking will focus on two areas: Rubidium-82 generators and moving technologies (such as Gamma Knife and Y-90 microspheres) from 10 CFR 35.1000 into the regulations. Currently, these and other technologies are regulated by guidance. ASTRO urged NRC to ensure that the fundamental requirements found in current licensing guidance documents are maintained.