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 PET tomographs by measuring the energy response spectrum of its detectors. Single scattered 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 in 3D acquisitions.