The first technetium-99m generator, unshielded, 1958. A Tc-99m pertechnetate solution is being eluted from Mo-99 molybdate bound to a chromatographic substrate. In the 1960s and 1970s Brookhaven researchers introduced and developed the first instant kit methods for rapid and convenient on-site labeling of technetium-99m radiopharmaceuticals. Today, technetium-99m is the most widely used imaging isotope in nuclear medicine.