Gamma-ray imaging exploiting the Compton effect

Another basic method uses directional information from a point-like positron source placed in front of an object to be examined. A position detector behind the source measures 511 keV γ rays from positron annihilation to determine the direction of the correlated 511 keV γ rays used to probe the object. Detecting the probing γ ray after Compton scattering off the object in time coincidence to the position determining γ ray enables to map the matter distribution in the object. Among other applications the method can be employed for the detection of land mines.