Antimatter
Antimatter, matter make everything; destroy each other releasing radiation; PET - positron emitting tomography uses this (positron is anti e-), used for brain scan; patient given e+ e+ emitting isotope, reaches brain via blood, each e+ travels mm until annihilated by e-, gamma photons prod. are detected; positron emitted when p+ turns n° in unstable nucleus (neutrino, v, also emitted) e+ emitters aren't natural,
manufactured by placing stable isotope (liquid, solid form) in path of p+ beam, nuclei absorbs some p+, become unstable