A technique for measuring the energy response of a PET tomograph using a compact scattering source

A technique is presented for verifying the energy calibration of a positron emission tomography (PET) scanner by measuring the energy response spectrum of its detectors. Singly scattered annihilation radiation provides a continuous energy reference source of coincident photons. The response of the scanner vs. scattering angle, and hence vs. energy is recorded within the sinogram. From these data, the position and resolution of discriminator levels which are set below 511 keV can be extracted. This is shown to be a useful diagnostic of the scanner's energy calibration, and of its response to scatter events in three dimensional (3-D) acquisitions.