The Reason of Photons Angular Distribution at Electron-Positron Annihilation in a Positron-Emission Tomograph

It is shown that photon angular distribution of electron-positron annihilation is consequence of Doppler’s effect in the reference frame of the electron and positron mass center. In the reference frame bound with electron the photon angular distribution is absent. But it is replaced by the Doppler’s shift of photon frequencies. The received results can be used in work of a positron-emission tomograph.