The introduction of PET scans that can image more than one radiotracer simultaneously could revolutionize oncology by enabling the first truly biologically individualized radiotherapy, explains Ceothán Gormley . Multiplexed PET A pure positron-emitting radiotracer generates 511 keV annihilation photons, with the PET scanner recording the photon pair as a coincident event called a “double” (blue). Some other positron-producing radiotracers emit a positron plus an additional gamma particle, creating a “triple” event (red). (Courtesy: E C Pratt et al. Nat. Biomed. Eng. 10.1038/s41551-023-01060-y )"> Multiplexed PET A pure positron-emitting radiotracer generates 511 keV annihilation photons, with the PET scanner recording the photon pair as a coincident event called a “double” (blue). Some other positron-producing radiotracers emit a positron plus an additional gamma particle, creating a “triple” event (red). (Courtesy: E C Pratt et al. Nat. Biomed. Eng.…