Rubidium-82

Rubidium-82 decays with a physical half-life of about 76 seconds, essentially entirely by positron emission, and behaves biologically as a potassium analogue that is extracted by viable myocardium in proportion to blood flow. Because the half-life is far too short to survive transport from a cyclotron, it is instead produced continuously by a strontium-82/rubidium-82 generator: the roughly 25-day parent 82Sr is bound to a column and the daughter is eluted with saline directly into an automated infusion system at the point of injection.

Alongside 13N-ammonia it is one of only two PET myocardial perfusion tracers with FDA approval in the United States (marketed as CardioGen-82, and successor generator products), and its extremely short half-life allows a full rest-and-pharmacologic-stress study to be completed in around 20-30 minutes with very high patient throughput, since a decayed dose clears within minutes and cannot be reused. Because trace amounts of the parent 82Sr and the contaminant 85Sr can break through the column, US regulations (10 CFR 35.204) cap the breakthrough at 0.02 microcurie of 82Sr and 0.2 microcurie of 85Sr per millicurie of 82Rb eluted, and generators require daily quality control.

Unlike an on-site cyclotron tracer, 82Rb needs no local radiochemistry infrastructure at all beyond the generator and infusion pump, which is why it has spread to community cardiac PET programmes that could never support 13N-ammonia or 15O-water.